Note: Descriptions are shown in the official language in which they were submitted.
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AUTOMATED MANUFACTURING CONTROL SYSTEM
Field of the invention
The present invention relates to PCB assembly plants using surface mount
technology.
Background of the invention
In a PCB assembly plant, there is a large number of electronic
components, which must be assembled on a PCB with the use of
automated production machines of various kinds, following a number of
pre-determined specifications and processes. These activities must be
performed for multiple products, each one having a unique combination
of materials and corresponding tooling and machine programs. In general
the complexity and risk of errors is directly proportional to the quantity of
different products that must be produced on a given assembly line and the
resulting production changeovers.
In most of these environments a human operator is the central element
responsible to interface with the various other elements of the
manufacturing system, including the movement of the material, the proper
operation of the equipment, the process control and the data transfer
between the various elements.
Manual data transfer
In a manufacturing environment, each time that a human is required to
perform a given task represents an opportunity for error. This is a growing
concern since the quantity and complexity of human interactions tend to
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increase with the increasing complexity of the products being
manufactured and the associated manufacturing systems.
The type of information that is associated with electronic components and
their packaging generally falls within one of the following categories
Identification data : Manufacturer, Part Number or Model, Lot Number,
etc.
Physical data : dimensions, quantity, temperature rating, etc.
Process data : Process step, history, status, time, process parameters,
expiration date, etc.
This data needs to be read, verified, modified, stored into a system or a
machine at multiple stages of the production process. This is normally
done through the intervention of an operator. In the simplest case, the data
will be read visually and written on a piece of paper or entered in a
computer system, with the use of a keyboard.
Auto ID Technology
In order to ease the burden for the operator and to reduce the risk of
human errors, there exist a number of Automatic Identification (Auto ID)
techniques that are used at various stages of a PCB assembly. These
systems, such as barcode, RFID, Optical Character Recognition, are often
used to provide a simple identification of an object and their primary
benefit in this case is to reduce the time and possible errors associated
with the manual entry of this information.
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Barcode Technology
One general inconvenient of using barcode labels to identify electronic
products is the fact that their installation and removal can generate static
electricity, which can damage sensitive electronic devices. In addition, a
sufficiently large flat area is required to apply a barcode label. This is
often restrictive in the world of electronics packaging due to the ongoing
trend toward smaller and denser products. Finally all barcode readers
require direct line-of sight with the barcode label. This can be a major
restriction toward complete automation of the reading operation.
RFID Technology
In addition to barcode labels, which have now become fairly common on
many standard materials and containers, some manufacturing systems
take advantage of the greater capabilities associated with the use of Radio
Frequency Identification (RFID) technology. A typical RFID system is
always made up of two components: the transponder, which is located on
the object to be identified and the interrogator or reader, which,
depending upon design and the technology used, may be a read or
write/read device (in this text - in accordance with common usage - the
data capture device is always referred to as the reader, regardless of
whether it can only read data or it is also capable of writing).
The RFID technology offers multiple benefits when compared to other
alternatives such as barcode. Some of the key benefits from the
perspective of factory automation include the greater flexibility in
packaging, greater and more flexible read-range and larger data storage
capability.
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Another very significant benefit of RFID technology is related to the read
and write capability (as opposed to read only). In addition to recording the
identity of the object, it is also possible to track its current state (e.g.
processing level, quality data), and the past and future (desired end state)
of the object.
There are two possible methods of controlling a system based upon object
data: central and decentral control. In the first method, all elements of the
system must be connected, through a network or other means, with a
common database in a central computer. In this case, a unique
identification number can be stored on a RFID transponder to access all
of the relevant data stored in the database.
In the second method, the use of readable and writable data carriers opens
up the possibility of controlling a system locally, i.e. completely
independently of the central process computer. Material and data flow
become interlinked. In a manufacturing environment this is very
significant since it may be impractical to have all machines and
manufacturing systems connected to a single network and central
database. This is especially true when a manufacturing process is made up
of multiple production steps which may be performed in separate
autonomous plants.
Tooling Identification
In the field of electronics manufacturing, a transponder is integrated in a
component feeder which is used to feed electronic components to an
automatic placement machine. Details of this prior art can be found in
patent US5713125. The benefits and shortcomings of this method can be
found hereinbelow in the section "Feeder Set-up Validation".
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Carrier Identification
There exist other applications and prior art relative to the use of RFID
technology to identify temporary production carriers. In one application, a
transponder is inserted in a magazine that cal-ries wafers through multiple
operations (ref. W00002236). In this case, the identification data is
relative to the main product being manufactured. In a different
application, transponders are inserted in a pallet, which carries material
between various processing stations. Other relevant prior art is described
in DE19745228.
These applications are limited to a single type of carrier and they offer a
limited range of applications and a limited interaction with external
systems.
General disadvantages of existing systems
A number of independent Auto ID based systems are commonly used in a
PCB assembly environment and the actual shortcomings of each system
will be reviewed in detail in the following section. The major drawback of
these methods however is the fact that they have not been designed from a
complete integrated systems approach which means that they cannot
address all of the data transfer applications of a given material and
associated earner during its complete life cycle. At the same time, many
systems are not designed to enable complete automation of the data
transfer and verification of the physical location of the material.
In the current electronics manufacturing environment, there are many
Auto ID applications using traditional barcode based identification for
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which the infrastructure and industry standards are well developed. There
are also a few isolated RFID applications but these systems tend to be
costly and difficult to implement due to the lack of standardization. As
such, it appears critical that any investment in RFID technology must be
leveraged by enabling multiple applications with the same transponders
and readers, and a higher level of automation than is possible with
barcode technology.
Example : Identification of trays and reels containing electronic
components
Depending on the relative size and cost of each type of components, they
may be individually marked during their manufacturing process (Fig. 2).
However in general the electronic components are tracked by batch
number and physically they are managed by individual reels, trays or
stacks of trays.
The reels and trays are standard containers which are used as a packaging
and shipping container as well as a convenient mean to feed components
to an automated placement machine.
It is a common practice for the manufacturers of electronic components to
apply a barcode label to the reel which contains the electronic
components (Figs. 3a and 3b). The data, which is normally found on the
barcode labels, includes the part number (supplier and/or customer), batch
number and quantity of the components on the reel. One common
problem in this case is the fact that there is no recognized standard
barcode label to identify reels of components. In order to simplify and
standardize the information format for the operators, some card assembly
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locations apply their own labels to each reel of component prior to
releasing them to the production area.
The standard IC trays, by virtue of their physical characteristics, do not
lend themselves well to traditional barcode identification. Their standard
outline does not offer a flat surface of sufficient size to apply a typical
barcode label (Fig. 4a). In cases like this, the identification data is
usually
not attached directly to the container. For example, the part number and
batch number can be written on a separate element such as a bag, sheet of
paper, edge of a shelf, etc. The obvious disadvantage of this method is
that it is easy for the operators to misplace or mix-up a tray during normal
handling and to lose the association between the data and the material.
The following section describes specific applications where the
manufacturing systems require proper identification and process control
associated with the reels and trays of components.
Tracking of moisture sensitive components
There exists a great variety of electronic components that are made up of
plastic or organic materials which tend to absorb ambient moisture in a
manufacturing environment. Because of the high temperatures
experienced during solder reflow of the components on the printed circuit
boards, these components can suffer internal damage in the form of
cracks and delamination if they are allowed to absorb too much moisture
prior to the actual reflow cycle. This problem has been well documented
and there are some industry standards that specify the proper shipping,
storage and handling procedures for moisture sensitive electronic
components.
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The standard procedure dictates that the moisture-sensitive components,
which are typically packaged in trays or reels, must be placed by the
manufacturer inside of sealed dry bags with desiccants and humidity
indicators. The bag seal date must be indicated on the label because there
is a maximum specified shelf life for storage of the components in the dry
bags (Fig. 4c). The user of these components, which is located at the card
assembly plant must verify that the expiration date has not been exceeded
prior to opening the package.
Once these bags are opened at the card assembly locations, there is a pre-
determined number of hours or days to which the components can be
exposed to ambient air prior to placement and reflow. The maximum
exposure time varies for each component and this data is also found on a
label which is located on the dry bag.
In a typical production environment, the actual number of hours and days
of exposure must be tracked manually for each individual tray and reel of
moisture sensitive components. This information can be recorded on
labels applied to the reels or protective bags or it can be logged on
separate sheets of paper.
There exist provisions in the standard to account for storage time in a dry
environment. This means that the clock of the total exposure time can be
suspended while the product is maintained in a dry cabinet for example
but the cumulative time must be tracked once the parts are returned to
production.
This manual tracking process is very cumbersome and not very reliable
which results in considerable inefficiencies. Furthermore, due to the high
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risk of human errors, the quality and reliability of the manufactured PCBs
is not completely assured.
Another common concern relative to moisture-sensitive components is
the risk associated with the rework procedure. Whenever components
have been over-exposed, the standard recommends that they be dried at a
given temperature for a given period of time. There are normally two
options available: a first drying process at room temperature and a faster
process at high temperature. A problem can arise whenever the plastic
Garner cannot stand the higher temperature. If the operator is not aware of
this limitation, he may use the wrong temperature which will result in
melting the carrier with the components and a significant waste of
valuable material.
Feeder Set-up Validation
On a typical placement machine, multiple reels of electronic components
must be installed on feeders and these feeders must be loaded at the
proper location on a placement machine (Figs. 8a and 8b). Since many
components have the same physical packaging, but different electrical
values, it is easy for an operator to load the wrong reel or the wrong
feeder at the wrong location and the placement machine may not be able
to detect the error. In this case, multiple PCBs can be assembled with the
wrong components. In order to avoid this kind of error, it is often required
that a different operator performs a second verification that the proper
parts are loaded at the proper location. This verification process takes
valuable operator and machine time and it is not completely error-free.
In order to reduce the above concerns, there exist versions of automated
verification systems that are aimed at reducing this risk of human errors.
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These systems are not available for every type of machine and they tend
to be proprietary to each model of equipment. The vast majority of these
systems require the operator to use a manual barcode reader to scan the
part number data located on the barcode label on the reel of each
component. This must be done at a specific point in time during the
process of loading the reels on the feeders or the feeders on the machine.
Depending on the exact characteristics of the placement machine and
associated feeders, this validation process may or may not need to be
repeated each time that the feeders are loaded or removed from the
machine. If the feeders themselves are equipped with a memory, the
material data can be temporarily kept on the feeder and automatically
recognized by the machine when the feeders are re-loaded. The major
disadvantage of all these systems is that the process must be repeated
every time that the reels are removed from the feeders. These
considerations are mostly significant in a high-mix production
environment where reels of components must be frequently removed and
re-loaded from the placement machine. Furthermore, there exists no
method to do this verification with some of the other types of carriers
which do not have any automatic identification, such as trays and tubes.
Partial tray information
A typical placement machine normally picks and places components,
using a placement head carrying one or more spindles fitted with vacuum
nozzles. This head usually picks components directly from the trays
located in a specific feeder and in a specific sequence, for example
starting with the top row up moving down and by column from left to
right. The placement machine normally starts with a full tray and it will
remember the pick position of the last component that was picked from a
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specific tray. This information is normally kept in the memory of the
machine until there is a power shutdown or whenever a tray is removed
from the machine.
In a production environment, it is very rare that a tray or a stack of trays
will contain the exact number of components required for a given
production batch. Hence, every time that a product change-over is
performed, there is a significant number of partial trays that are removed
from the machine to be kept in temporary storage. In order to insure a
"first in, first out" material usage and to avoid the multiplication of
partial
trays, they are normally the first ones to be re-loaded in the placement
machine for the next production run that requires this specific part
number. Since the placement machine cannot recognize whether a partial
tray or a full tray has been loaded, the operator must enter this data
through the user interface of the placement machine. The operator must
look at the partial tray and indicate exactly which pockets are empty and
consequently where the machine will start picking. This step must be
repeated for each partial tray that is loaded in the machine which
consumes valuable operator and machine time during product change-
over. In addition, there is a risk that the operator will forget to enter the
data or enter wrong data in the placement machine. This can result in
further production down-time and even damaging fragile and expensive
components.
Component traceability and real-time inventory on a placement machine
In addition to the part number data located on the barcode labels of the
reels, some placement machines can also use additional information, such
as lot or batch number and quantity. In one example, the lot number is
read from the label at the same time as the part number and this data is
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used to keep a history file containing full traceability of which lot of
component was used to build which lot of PCB. This information can be
required due to the critical nature of the product being manufactured, such
as military or medical devices.
In a similar system, the quantity of the components is also read from the
barcode label at the same time as the part number and this information is
kept in a local memory in the feeder or in a central database in the
machine. This data can be updated as the machine is picking and placing
components from that specific feeder. Some systems offer the possibility
of re-printing a new barcode label with the revised quantity when the
reels are removed from the feeder.
Once again, there exists no such system for components that are packaged
in other types of carriers without automatic identification, such as trays
and tubes.
Inventory and physical location of material in production
In the process of PCB assembly, it is common to have hundreds of
different electronic components that must be assembled on a single PCB.
Often, a critical production run cannot be started because of only one
missing type of component. In some cases it is possible that there exists
another reel or tray of components somewhere on the production floor but
it cannot be quickly located.
In a typical manufacturing plant, the inventory control system can identify
whether a specific lot of material has been released from the stockroom to
the production area but this does not provide a sufficient level of detail to
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quickly and efficiently locate the said material or to find out the
remaining quantity.
In some cases, the control systems that are associated with the placement
equipment can provide reports of the exact types and quantities of
components that are located on a specific placement machine. However,
this information is lost as soon as the reels and trays are removed from the
machine (or when the reels are removed from the feeders if they have a
local memory). In addition it is not possible to obtain a rapid and accurate
inventory of the trays and reels that are stored in various boxes, shelves,
carts, cabinets or other temporary storage areas on the production line.
In addition, in order to perform this type of physical inventory, it is
required that each reel be handled by an operator. The reels are normally
stored side-by-side and they must be pulled from their storage location to
enable the labels to be visually seen or to provide the required line-of
sight for the barcode reader. Because of the nature of a reel, it is not
possible either to determine the remaining quantity of components
without unwinding the tape.
There also exist some handling difficulties specific to the trays. In most
cases, the components are held within their respective pockets by the
bottom of the next tray which is stacked on top of it. This means that
there is normally an empty tray on top of each stack that is used as a
protective cover. This cover tray may prevent the operator from seeing
how many parts are left on the first tray which is often partially filled. If
there are no top trays, then the parts can easily be dislodged from their
pockets through normal handling and cause damage to the sensitive
component leads.
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The above considerations can lead to a significant waste of time for
employees trying to locate material, to potentially damaging components,
and to a resulting production downtime and subsequent delivery
problems.
Inter plant information transfer (Fig. 7)
In general, the electronic components and/or its packaging have to be
transferred from one facility to another for subsequent processing. In this
case it becomes even more difficult to transfer and share product and
process information through a central network.
Semiconductor Packaging Plant to Card Assembly Plant
The semiconductor packaging plant is often referred to as the first level of
electronics packaging. This level of production normally starts with
complete wafers received from the wafer manufacturing plant. The end
product is a batch or lot of complete electronic components, which is
properly packaged in reels or trays and ready to be assembled on a printed
circuit board (PCB). The information required by the next level of
assembly, which is the card assembly plant, is located on one or more
labels which may be applied directly on the reel or on the protective bags
and boxes.
Some of the information on these labels is available in a barcode format,
which typically includes, but is not limited to : supplier ID, part number
(supplier and customer), lot number, quantity. Additional data is
sometimes printed on the label only in a text format, for example JEDEC
moisture sensitivity level, maximum exposure time, packaging date and
time, etc.
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Tray Manufacturer to Semiconductor Packaging Plant
In this application, the tray manufacturer is the company that makes the
plastic injection-moulded container. There are many basic parameters
associated with each tray that can be required by the semiconductor
packaging plant.
In many cases, the basic information data relative to the tray itself is
embossed in the plastic moulding. This can include the name or logo of
the manufacturer, the part number or model description, the engineering
change or revision number, the batch number or date of manufacture (e.g.
Month/Year), the maximum temperature rating, etc.
It is important to note that during the later steps of the semiconductor
packaging process, the tray can be used as a component carrier. In this
case, and prior to final packaging, the operators must verify that they are
using the proper type of tray. If the wrong tray is used, this can result in
damage to the electronic components during later shipment and
processing. This can cause mechanical damage to sensitive component
leads.
Another common issue relates to high temperature processing such as
drying moisture sensitive components prior to final packaging in sealed
dry bags. This operation can be done at a temperature of 125°C and the
operator must ensure that the tray is rated for this temperature. Otherwise
the tray will melt and damage the components that it contains.
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Recycling of trays and reels
It is common practice for the card assembly plants to collect all of the
empty containers and to send them to a recycling company. This will
typically consist of large boxes full of mixed trays and reels of various
types and models. The recycling company will start by sorting the trays,
according to the manufacturer, part number or model description, EC#,
etc. The trays and reels will also be inspected and cleaned before being
resold to the original manufacturer or directly to a semiconductor
packaging plant.
Design and assembly data
In addition to the identification elements of the materials required during
normal production, there is a large quantity of design data required for the
initial set-up of the various production systems and machines. This data is
normally stored in each machine program database for later use
In most cases, the components will be placed and/or removed from the
tray by automatic machines. In order to create the initial machine
program, some physical dimensions data must be measured precisely on
the tray, for example the respective location of each pocket of the tray.
This information can be transferred directly from the tray manufacturer to
the user via a detailed mechanical drawing and a technician or
programmer must enter this data in the machine.
In the case of electronic components, it is very common for the placement
machines to use sophisticated vision systems to verify that the proper type
of component is being placed, to inspect its critical dimensions, and to
perform a best fit alignment based on actual physical dimensions. In
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many cases, this data must be obtained by measuring individual
components or it may be available from a detailed mechanical drawing
supplied by the component manufacturer. In both cases a technician or
programmer must input all of the required elements of information for
each new component or product.
Summary of the invention
The present invention relates to a system which greatly reduces the level
of interaction required from an operator relative to the data exchange,
physical verification and process control associated with the movement of
electronic components, tooling and operators in a PCB assembly plant.
This is achieved by the use of data carriers which are attached to the
components, their packaging, including reels, trays and tubes, the
removable tooling and the operators. These data carriers can store all the
relevant identification, material and production data required by the
various elements of the manufacturing system. Various readers, integrated
with controllers and application software, are located at strategic points of
the production area, including production equipment and storage areas, to
enable automatic data transfer and physical verification that the right
material is at the right place at the right time, using the right tooling.
The present invention also provides a data carrying device adapted to be
temporarily attached to trays, reels, etc., and comprising a support
member adapted to be detachably mounted to the trays, reels, etc., and a
transponder, or the like, carried by the support member. More
specifically, the support member can take the form of a clip adapted to
grip a rail of a tray, or a pouch adapted to be adhesively mounted to a side
of a reel.
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Brief Descriution of the drawings
Having thus generally described the nature of the invention, reference will
now be made to the accompanying drawings, showing by way of
illustration a preferred embodiment thereof, and in which:
Fig. 1 a shows a Printed Circuit Board (PCB);
Fig. 2 shows an electronic component and identification;
Fig. 3a shows a tape and reel packaging;
Fig. 3b shows a reel identification and packaging;
Fig. 4a shows a tray;
Fig. 4b shows a tray identification and packaging;
Fig. 4c shows moisture sensitive labels for sealed bags and shipping
boxes;
Fig. 5 shows tubes and cassettes;
Fig. 6 shows a material flow in a card assembly plant;
Fig. 7 shows a material flow inter-plant;
Fig. 8a shows a placement machine;
Fig. 8b shows a tape feeder for a placement machine;
Fig. 9a shows a clip for a tray;
Fig. 9b shows a sliding clip for tray;
Fig. 9c shows a supporting pouch for a reel;
Fig. 9d shows a peel-off supporting pouch for a reel;
Fig. 10 shows a flowchart for moisture sensitive components tracking
system;
Fig. 11 a shows a base station comprised of a reader and controller; and
Fig. 1 lb shows an antenna, the coupling element of a reader.
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Description of the~referred embodiments
The invention will now be described with reference to its application with
the assembly of printed circuit boards.
In general, the present invention relates to a material data communication
system which is part of a production control system. The material data
communication system includes data capture devices, control modules,
power supplies, communication hardware and software to transfer the
captured data. In this instance, the data capture devices employ radio
frequency identification (RFID) tracking technology for capturing data
from passive data-carrying devices which are attached to the production
material. In the following text, we will refer only to the RFID technology,
although any other technology could be used for data transfer and capture.
Components of the control system
1. The transponder, which is attached to the components, their packaging
(including reels, tray, tubes and cassettes), the removable tooling and the
operators. 2. The readers, which are located at strategic points of the
manufacturing system
3. The controllers which process the data acquired by the readers
Definition of transponder
The transponder, which represents the actual data-carrying device of an
RFID system, normally consists of a coupling element and an electronic
microchip. When the transponder, which does not usually possess its own
voltage supply (battery), is not within the interrogation zone of a reader, it
is totally passive. The transponder is only activated when it is within the
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interrogation zone of a reader. The power required to activate the
transponder is supplied to the transponder through the coupling unit
(contact-less) as is the timing pulse and data.
The transponder also includes a protective packaging for the electronic
device and associated coupling element (antenna), and a mechanical
structure to facilitate its attachment to the object to be identified. The
attachment method can be temporary or permanent, based on the most
practical and cost-effective solution for each application.
Definition of reader
The interrogator or reader, depending upon design and the technology
used, may be a read or write/read device. A reader typically contains a
radio frequency module (transmitter and receiver), a control unit and a
coupling element to the transponder. In addition, many readers are fitted
with an additional interface (parallel or serial communication) to enable
them to forward the data received to another system (PC, robot control
system, etc.).
The coupling element (antenna) must be optimized for each application in
accordance with the basic requirements of the specific RFID technology
(frequency), the mechanical constraints and the electromagnetic
limitations and interferences, in order to provide an adequate read range
in combination with the transponder. In some applications, many
transponders can be at the same time in the range of a reader and the
system must be designed with the appropriate anti-collision software and
hardware.
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Definition of controller
A controller is the system that receives and processes the data acquired by
the reader. In the simplest form, the controller can be integrated with the
reader in a portable hand-held unit and this can be used only to display
information contained on a transponder. This portable unit can be fully
autonomous or it can be connected, continuously or punctually, to a host
computer through a docking station, radio-frequency communication or
other means.
The controller can be a fixed stand-alone system integrated with a reader
into a conveyor, production machine, storage area or any other strategic
location. In this case, the controller contains a CPU and application
software to accomplish a given function including reading or writing
information on a transponder. The controller can also be a central host
computer which is used for enterprise data management or dedicated to a
specific function such as statistical process control.
Due to the nature of a PCB assembly plant, a typical application may
include multiple controllers, with a combination of stand-alone and
centralized software controls. These controllers can be, if required, linked
together, or to any other computer or controlling unit, in order to access
databases, share data or simply send commands or status.
Semi-Automatic RlW operation
Depending on the nature of the application, it may be preferable to use a
semi-automatic reader. The semi-automatic designation means that the
system requires the intervention of an operator to perform the read/write
cycle. This intervention can simply consist of bringing one or more
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objects with a transponder in the field of a specific reader or to bring a
portable reader close to one or more specific transponders. The operator
intervention can only consist of starting a specific read/write cycle by
pushing a button or selecting a proper software command from a PC user
interface. An example of such a reader is shown in Fig. l la. The coupling
device (antenna) of this station is shown in Fig. 1 lb.
Fully Automatic RlW operation
A fully automatic read/write operation implies that no human intervention
is required. This is applicable when a reader is integrated, for example, in
a conveyor or automated machine. The read/write cycle may be
continuous or it can be triggered by appropriate sensors and software or
other automatic control systems.
Modular System Architecture
In order to maximize the benefits of an investment in a system based on
this invention, it is preferable that it can handle many different
applications.
The typical data structure would be different for each type of packaging
and transponder. For a given type, it would be very beneficial to have a
single data structure that can accommodate all potential applications,
closed-loop and inter-plant. In this context, it must be recognized that the
same packaging may be used in more than one environment and that
some data elements might be common to multiple steps while others may
be required only for individual applications.
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IS' example : Transponders on reels and trays
Given the existing infrastructure of barcode identification and the
relatively high unit cost of a typical transponder, the present example is
based on the use of a temporary mean to attach the transponder, with
different designs adapted to each format of packaging. In this case, the
transponders are used in a closed loop cycle. For this reason, the benefits
of the system must be more important that the additional cost associated
with the attachment and removal of the transponders, including the initial
data entry. Any application would become even more advantageous if the
card assembly plant can receive the reels and trays from its suppliers with
the transponders already attached thereto and with the data already
present in the proper format.
In this application it is important that the shape and location of the
transponders do not affect the normal handling, storage and use of the
reels and trays during production. The ease of use (attachment and
removal) of these transponders is another important factor.
The transponder for reels must not interfere with most common tape
feeders of automated placement equipment. The transponder for trays
must allow the trays to be stacked and it must not interfere with most
common tray feeders of automated placement equipment.
Figs. 9a and 9c illustrate proposed devices to attach the transponders
temporarily respectively to the trays and reels:
a) In the first case (Fig. 9a), the tag is encapsulated in a plastic clip
that will be attached to the trays. View 1 of Fig. 9a shows the clip
attached to the tray, whereas View 2 includes a pair of perspective
views of the clip alone and View 3 includes side and rear views
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thereof. This clip is made out of process compatible materials that
are ESD (electrostatic discharge) sensitive, that can sustain at least
125 °C and that will not contaminate parts with ionic residues or
other incompatible contaminants. This clip can also be sized to
accommodate a small bar code or label where tray or part
identification can be written. This clip is shaped in a manner that it
will accommodate the JEDEC standard for the trays by gripping to
one of the rails at the two ends of the tray. This is done by the L
shape at the end of the clip that is designed with the right
tolerances to fit the female portion of the rail of a JEDEC standard
tray. This L shape can be seen in Views 2 and 3 of Fig. 9a (i.e. the
3D views and the side view). As the cross-section of the rail of the
tray is the same along it's whole length, the clip can slide thereon
and be placed anywhere on this rail. In order to insert the clip, one
can slide it from one end of the rail. Another way to place this clip
on the tray would be to squeeze it such as to open it wide enough
so it clears the larger portion of the rail, then insert it to mate with
the female portion of the rail on the other side of this larger portion
and finally release it so that it grips the rail. Similarly to the first
method of insertion, to remove the clip, it will have to be slid to
the end of the rail. In order to accommodate all tolerances of this
rail, the clip is spring loaded. In Fig. 9a, the loading is given by
standard coil springs that are inserted between the two moving
parts. It also could be given by any other type of spring, as long as
the tolerances and the force match those required. Another
example of loading is given in Fig. 9b. The clip is built in only one
part that is spring loaded with an integral spring. The properties of
this spring are given by its shape and the properties of the material
used. This clip uses the same features as the earlier clip of Fig. 9a
to grip to the tray. Another way to build this clip, not illustrated
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here, would be to use a metal that has the right properties to give
the right loading. This clip would also use the described features of
the tray to grip it.
b) In the second case (Figs. 9c and 9d), the transponder is in the form
of a small disk, the size of a nickel (5 ø). It will be inserted in an
adhesive holding pouch that will accommodate the transponder
temporarily. This pouch is made out of ESD sensitive material,
designed and sized to accept the transponder easily, hold it
strongly to the reel while in use on the production line and release
it easily at the end. The first design in Fig. 9c is made with a flap
on the non adhesive side of the pouch. This flap, once the
transponder is inserted, is turned over and glued on the adhesive
portion, thereby covering a small portion of the adhesive material
and closing the open end of the pouch. Using the rest of the
adhesive material, the pouch is glued to the reel. In order to ease
the removal of the transponder, once it is not required on the reel
anymore, the pouch can be equipped with dotted lines or other
means to weaken the plastic of the pouch. The second design
shown in Fig. 9c is a straight pouch with an opening at one end. It
also has a slot on the sticky side of the pouch that will enable one
to enter the transponder easily (back loading). Once the pouch is
glued, this slot is not available anymore. The pouch is sized to be
barely larger than the diameter of the transponder and the latter
will therefore not fall off the pouch without a human intervention.
In order to remove the transponder, one can simply push it towards
the open end (top end of Design 2 in Fig. 9c). Other ways to
remove the transponder from a pouch include the weakening of the
top side of the pouch making it easy to peel off, as shown in Fig.
9d. There also exists other means to hold the transponder on the
reel inspired by the adhesive pouches, such as for instance the use
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of double sided sticky tape (reusable or non-reusable), VelcroTM,
reusable or non-reusable glue applied directly on the transponder
or any other means to hold or glue the transponder to a flat surface.
Example of data structure : transponder attached to a tray with electronic
components
Tray Identification
Manufacturer
Part number
Revision or Engineering change number
Date code
Component Identification
Manufacturer
Manufacturer part number
Customer part number
Date code or lot number
Quantity
Partial tray 1 S' row
Partial tray 1 S' column
Process Data
JEDEC level
Maximum exposure time
Current exposure time
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Status flag (inside dry environment or normal production floor)
Attachment of the transponders for trays and reels
In this application, the transponders are first attached to reels and trays
when the latter are unpackaged, i.e. before being released to the
manufacturing area. If the trays are always handled in stacks, and given
that the placement machine is always starting to pick from the top tray of
a stack, it is possible to attach only one transponder to the bottom tray of
each stack. This reduces the number of transponders to attach and the
associated handling of the trays.
Transfer of Identification Data
After the transponders have been attached, the information to be entered
on the transponders is normally taken from the labels located on the bags
or the box containing the reels and trays. Alternatively, this information
can be transferred before the transponders are attached. They would then
follow the material by being attached to the bags or boxes, using a pouch
or some other means. The attachment to the trays, tubes or reel would
then take place when the parts are unpacked. This data is either scanned
with a standard barcode reader, entered manually or both, and it is
transferred to the transponder. This can be achieved with the use of a set-
up station, equipped with a reader, personal computer and application
software (Fig. l la). This information typically includes the part number,
date code and quantity and it can be used for multiple applications,
including, but not limited to the following:
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Material Identification
The first benefit from this is the ability to clearly identify the content of
any particular tray, anywhere on the production floor. A portable reader
of RFID tags can be used to display the PN (i.e. Part Number), the LN
(i.e. Lot Number) and the Qty (i.e. Quantity) associated with each
transponder. This was not previously possible due to the absence of
material identification on a standard plastic tray. This information can
also be listed on a computer display. This list would be refreshed as the
information is changed and the material is moved.
Moisture sensitive components tracking system (Fig. I D)
There exists a great variety of electronic components that are made with
plastic and organic materials which absorb ambient moisture in a
manufacturing environment. Because of the high temperatures
experienced during solder reflow of the components on the printed circuit
boards, these components can suffer internal damage in the form of
cracks and delaminations if they are allowed to absorb too much moisture
prior to the actual reflow cycle. This problem has been well documented
and there are some industry standards that specify the proper shipping,
storage and handling procedures for moisture sensitive electronic
components.
The standard procedure dictates that the moisture-sensitive components,
which are typically packaged in trays or reels, must be placed by the
manufacturer inside of sealed dry bags with desiccants and humidity
indicators. The bag seal date must be indicated on the label because there
is a maximum specified shelf life for storage of the components in the dry
bags (Fig. 4c). The user of these components, which is located at the card
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assembly plant must verify that the expiration date has not been exceeded
prior to opening the package.
Once these bags are opened at the card assembly locations, there is a pre-
determined number of hours or days to which the components can be
exposed to ambient air prior to placement and reflow. The maximum
exposure time varies for each component. This information is indicated
on a label which is located on the dry bag.
In a typical production environment, the actual number of hours and days
of exposure must be tracked for each individual tray and reel of moisture
sensitive components. There exist provisions in the standard to account
for storage time in a dry environment. This means that the clock of the
total exposure time can be suspended while the product is maintained in a
dry cabinet for example but the cumulative time must be tracked once the
parts are returned to production.
For components that are categorized to be moisture-sensitive, the bags
containing the components in trays or reels are typically opened only
when the material is required in production. In this case, the standard
level of sensitivity and the maximum exposure time in hours or days are
also clearly indicated on the bag or box containing the reels or trays. This
information is transferred on the transponders at the same time as the
material identification. A record of the time and date relative to the
opening and the maximum exposure limit is transferred when the bag is
opened. Additional information relative to the carriers themselves, such as
temperature rating, can be read directly from the carriers and written on
the transponders at the same time.
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The same, or a similar, set-up station is used to record material movement
in and out of a controlled dry air environment. The software takes into
account the fact that the clock of total exposed time is suspended when
the moisture-sensitive components are properly stored. It will furthermore
accommodate all dispositions of the standard for moisture sensitive parts.
A manual portable reader can be used to verify the remaining exposure
time of each individual tray and reel on the production floor. This
verification can be done during a new set-up or at specified intervals of
time (once per shift). This information can also be found on a
computerized list that specifies all moisture sensitive devices presently
used and their respective remaining exposure time. This list could also
include the location of the parts (machine and feeder location). Additional
information could be added, as required. Similarly, lists of parts in dry
cabinets, ovens and dry bags could be added with the proper information
for each process (exposure time remaining, location, bake time remaining,
quantity, etc.). These lists would provide a real-time, centralized and
easy-to-access database of all moisture sensitive devices in an assembly
plant. They would, in a single operation, enable any operator to
understand the physical inventory, the location of the parts and their
status.
A further refinement of this system would take into account the ambient
temperature and humidity measured by sensors on the production floor
and would adjust the expiration date and time accordingly, as specified by
the standard.
Whenever components reach their exposure limit, provided that this
information is written on the transponder, the system can verify whether
the carrier is capable to withstand the high drying temperature and
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prevent an operator from using a high temperature process with a low
temperature tray.
Such a system can also ensure that the right process steps are followed in
the right order with the moisture sensitive devices. Different flags can be
used to ensure that conflicting processes are not permitted. For example,
one should not be able to put parts in a dry cabinet if the parts are still
loaded on a machine or in a bake oven. Another example is the use of the
bake process. The standard allows only one bake process without
supplier's consultation. Once again, the use of flags enables this control.
Integration to dry cabinet, drying oven and placement machine
For the previous application, a higher level of automation can be achieved
by integrating readers and a suitable controller in the dry storage areas,
drying oven and in the placement machine.
This integration can be done at different levels. In the simplest form, it
can consist of a stand-alone controller with a dedicated reader and
application software, located in close proximity to the dry cabinet, drying
oven or placement machine. In this case, the operator needs to scan the
transponders by bringing the trays or reels in proximity to the reader,
within the range of the antenna, each time that the material is moved in or
out.
Depending on the application the software may be used simply to update
the information in a database or on the transponder. For example, when
reels and trays are scanned before being placed inside a dry storage area,
the status flag is switched to "inside dry environment". Whenever the
same trays and reels are scanned after being taken out of the dry storage
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area, the expiration date and time are recalculated based on a pre-
determined set of rules, and reset on the transponder. At the same time the
status flag is switched back to "in normal production environment". The
status flag is used to make sure that the operator did not forget to scan the
transponders when the material was entered or removed from dry storage.
According to the needs of each specific application, the user interface
may consist of a simple set of visual or audible signs to indicate a "good
read" or to indicate a process alarm. It may also include a complete
display and keyboard. In this application, a display could, for example,
indicate the remaining exposure time each time that the material is
removed from dry storage.
In the case of a production equipment which possess its own controller or
CPU, the reader/controllers may also be directly connected to the
equipment, using a standard (RS-232, SECS/GEM) or custom
communication hardware and software interface. This would enable
automatic data transfer and potentially request actions from the
production machine, such as the activation of an interlock or the
generation of error messages. The highest level of integration consists of
installing a reader directly inside the machine envelope and to use the
controller and software of the actual production machine to perform the
appropriate process control.
By integrating antennas at strategic locations, it is possible to transfer the
necessary data and update the information on the transponders with no
operator intervention, thereby improving the efficiency of the operations
and reducing the risk of errors. The following examples demonstrate
practical solutions relative to the control of moisture-sensitive
components.
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On a placement machine, before a reel or tray of moisture-sensitive parts
exceed the specified time limit, a pre-alarm can be generated to advise the
operator to take appropriate action. If the material is expired, the system
can also engage an interlock to prevent the placement of the components
by the machine.
On a dry storage area, such as a dry cabinet, a reader and associated
controller can be integrated to automatically register the material moving
in and out of the cabinet and to update the expiration date and time and
status flag on the transponders accordingly.
On a drying oven, a reader and associated controller can be integrated to
automatically register the material being dried and to reset the expiration
date once the drying cycle is completed. In addition, it can also prevent
use of the oven if the container (tray or reel) is not compatible with the set
temperature.
Feeder Set-up halidation
A further development of the integration to a placement equipment
includes a feeder set-up validation. In this application, the transfer of the
part number information from the transponder on a reel can be made
faster and in a more automated manner than with a traditional barcode
label. This can be done through the use of a dedicated set-up station or
hand-held reader, whichever is more practical for the specific machine.
This application can also be extended to components in trays, which is
not possible with prior methods.
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A further refinement of this application consists of integrating readers
directly onto the placement machine thereby enabling complete
automation of the verification process.
Set-up validation
The previous application can be taken further if the removable tooling is
tagged. The validation would not only be for the raw material but could
include the validation that all the right peripherals are used. All this could
be triggered automatically if the product being assembled was tagged as
well. It would then identify itself and start the validation process.
Update of Remaining Quantity
Another benefit from this new approach is to allow the update of the
remaining quantity directly on the transponder on the reels, even when
they are removed from the feeders, without having to manually write the
revised quantity on a label or to reprint a new barcode label. This also
enables a similar application for components in trays which is not
possible with prior methods. Ultimately, the readers can be fully
integrated in the placement equipment such that no local memory is
required on the feeders and no manual scanning operation is required
from the operator.
Partial tray information
This is a further development from the present invention relative to the
integration with a placement machine. Every time that a partial tray needs
to be removed from the machine, the information relative to the last
component picked is first transferred to the transponder attached to the
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tray. This data can be recorded with a row number and column number
for example. Then, the tray can be stored temporarily and the partial tray
information is uploaded to the placement machine during the next set-up.
This system reduces significantly the operator intervention, which reduces
the set-up time and potential damage to components.
Traceability
Yet another further development is to transfer the lot number or batch
number information associated with each reel to enable complete
traceability of the components used to assemble a specific batch or serial
number of PCB. Once again, this is also true for components in trays, and
this is not possible with prior methods. This process could be fully
automated if the PCBs were tagged as well.
Real-time inventory control and physical location of material in WIP
The information on each transponder can also enable real time inventory
control of the tagged material on the production floor. As described in the
previous placement machine integration, the exact quantity and location
of each reel and tray of components loaded on every machine is already
available locally. The next step consists of integrating readers at other
material storage locations, which mainly consist of various shelves,
cabinets and carts. This can be achieved in many different configurations,
by increasing the number of readers based on the level of resolution that
is required and the overall cost of the system. At one extreme, the
transponders can be scanned with a hand-held reader when they enter a
given section of the manufacturing floor. Another option is to integrate
one reader for each storage unit, each shelf, each section of each shelf,
etc. In order to reduce the cost of the overall system, many antennas can
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be multiplexed through a single read/write card controller. The integration
of all the individual elements in a single network allows for centralized
real-time inventory control.
A storage area can include additional features to simplify the interface
with the operator. For example LEDs can be located at each individual
storage area to indicate the location where the material needs to be placed
or removed. A more sophisticated system can include a series of digital
displays to show information relative to the material in a given storage
area. Computer lists with defined location can also be used.
One of the obvious benefits of this system includes the ability to rapidly
locate any specific reel or tray of components.
Inter plant information transfer (Fig. 7)
The above applications can be further enhanced by using the same
transponders between various manufacturing locations in the supply
chain.
In this case, the transponders can still be attached temporarily but it may
be more practical to attach them permanently. This can be done through
the use of an external device that is attached to the object to track.
Another alternative is to insert the transponder directly inside the object,
during the initial fabrication process (e.g. plastic moulding) or at a
subsequent operation, such as drilling a hole in the earner.
In the context of an inter-plant application it becomes critical that all the
elements are designed to be compatible with each other and to
accommodate the various requirements from each different application.
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This means that the transponders, readers and associated software must be
designed as a complete system. The common elements of an inter-plant
system are the transponder technology and its communication and data
structure.
Semiconductor Packaging Plant to Card Assembly Plant
From the perspective of the card assembly plant, it would be very
beneficial to receive, from their component suppliers, the trays and reels
already equipped with transponders containing the information required,
such as part number, lot number, quantity, JEDEC moisture sensitivity
level, packaging date and time, etc. In this case, all the relevant data can
be used to automate the receiving of the components and initiate the
proper applications.
Carrier Manufacturer to Semiconductor Packaging Plant
In one embodiment of the present invention, all the data relative to the
manufacture of the tray is written directly on the transponder at some
point in the manufacturing process. This information may include the
following : manufacturer, part number, EC#, description, physical
dimensions, maximum temperature rating, etc.. This information can be
read by an operator, using a hand-held reader, to insure that the proper
tray is being used for the proper product in a given process.
At the same time, the transponder can be used to store information
relative to the components that it contains, including identification data,
process data, physical data, etc. From a different perspective, similar
applications and benefits can be derived during the component
manufacturing process as was described in the card assembly process.
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A further refinement of this invention consists of integrating readers in
the automated equipment that handles the trays at various operations.
Recycling of trays and reels
Recycling companies can greatly benefit from the presence of a
transponder on the trays to be recycled. This allows a rapid and accurate
recognition and classification of any tray such that it can be sorted out
more efficiently. This identification method can eventually enable higher
levels of automation and reduce errors in the sorting process.
Before returning the trays to the original manufacturer or directly to a
semiconductor packaging plant, the recycling company can verify that the
proper information is indicated on the transponder attached to the tray and
it can remove any additional data that was associated with the previous
usage.
For example, the information to be left on the transponder might include
the same data that was provided by the original tray manufacturer, as
described earlier. It may also contain information relative to the recycling
process, such as the recycling company, the number of recycling loops,
etc. However, it might be desirable to remove other data that is no longer
relevant such as the data relative to the electronic components that it
contained.
Design and assembly data
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Provided that there is a sufficiently large memory available on the
transponder, the containers can also be used to automatically transfer the
basic data required for the initial set-up of the production equipment.
Whenever a new component is loaded on a placement machine this allows
the automatic transfer of the required information such that the machine
can program itself without human intervention. This can include all
physical dimensions relative to a shipping tray, including the data relative
to the matrix of rows and columns. It can also include the data relative to
the components themselves, including package type, number of leads,
lead length, etc.
Another alternative consists of using the basic material identification
(manufacturer, part number) to access an external database which
contains the required design data in a format that can be uploaded to the
production machine. This database can be maintained by the tray and
component manufacturers and it can be accessed through the Internet.
Automatic machine start-up
Furthermore, from the previous application, if the PCBs are tagged, the
appropriate information could be available from the tag or from an
accessed database in order to program the placement machine for a given
part number. Once the machine is loaded with the PCB and the
appropriate raw material, it programs itself to do the assembly.
Routing of parts
Once the PCBs are tagged, the routing to the next process step can be
automated. The PCB can route itself, depending on certain quality or
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process reports. For example, a decision to go to inspection, rework or the
next assembly step can be taken, depending on certain results in the actual
process step.
Quality certificate
It would also be possible to keep track that the parts have seen all the
required process steps and passed all quality checks. This would ensure
that the outgoing product conforms to quality standards, similar to a
personalized ISO 9000 certificate.
Integration to the business process
This invention, as it relates to data acquisition and processing, will
influence greatly the business processes in a manufacturing plant. It can
influence one or many of the following processes:
1. Shop floor management system. This system will now be linked to
a real time data acquisition system. It will then be possible to know
various information such as the following:
a. Yield loss at a given operation
b. Percentage of reworked parts
c. Raw material used per lot
d. Units produced per hour at a given operation
e. Production lots movements
f. Estimate of the time remaining before a job comes out of
production
g. Overall equipment efficiency
h. Raw material movements
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2. Production line and cost improvement. With the information listed
above, it will be possible to know exactly where are the pinch
points and the less efficient sectors. The line improvements can
then be directed to the right places.
3. New product introduction. As all the product information can be
available directly to the different process centres and equipment, a
new product can program itself on the automated equipment with
no or minimal human intervention. This makes it possible to
introduce a new product rapidly on a manufacturing line.
4. Prototyping and small production lots. Furthermore, machine
changeover from a product part number to a different one can be
automated. This reduces greatly the time needed for a changeover
and makes it possible and economically viable to reduce the
production lot size.
5. Transparency with the customers. As all this information is
available in real time, it will be possible to post it on the Internet,
with the right security access, available to customers.
6. WIP and inventory tracking. This information can now be
uploaded in real time to a central system (ERP, MRP or other).
7. Costing. As all the information relative to raw material utilization,
yield (percentage of good parts), rework, tool utilization and labour
is available for any given lot, it is possible to determine precisely
it's cost.
8. Projections. Having all this historical information available, it will
be much easier to make projections on the following:
a. Equipment and tooling required for a given amount of
production
b. Manpower required
c. Raw material required
d. Costing
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