Note: Descriptions are shown in the official language in which they were submitted.
1~8gl~ i
An improvement in the prior art of temperature~pressure
laminated multi-layer printed circuit boards is shown and
claimed in U.S. Patent No. 3,660,726 issued May 2, 1972 and
assigned to the assignee of the present invention. In general,
the aforementioned patent involves a technique for forming a
multi-layer board by stacking a plurality of single layer
; printed circuit boards separated by insulative sheets, so
that a plurality of plated through holes in each of the boards
are axially aligned. ~n electrical contact, such as that
1~ used in a printed circuit card edge connector, is press fitted
down through each of the aligned plated through holes. Fric-
tional engagement of the contacts with the plated walls of
the holes mechanically joins the boards into a single un-
itary structure and connects each one of the axially aligned
~¦ conductive holes to form an electrical interconnection be-
tween the circuitry printed upon each one of the boards which
~¦ is connected to a plated hole.
When printed circuit card edge connectors, such as shown
in U.S. Patent No. 3,671,917 issued June 20, 1972 to A~mon et al
are arrayed on a backpanel (motherboard) to receive and connect
component bearing printed circuit cards (daughterboards), each
contact is either unused, connected to ground potential,
connected to a power supply voltage potential, or isolated from
¦ both supply voltages and grounds to carry a varying signal
voltage.
¦ Today, most of the active components mounted on daughter-
¦ boards are semiconductive in nature and, hence, require relative-
l ly low power supply voltages, e.g., on the order of 2 volts
¦ above ground. However, because of the large number of such
¦ components associated with each backpanel the power supply
~ distribution current requirements become quite large, e.g.,
! on the order of 50-300 amps. When, for certain applications,
very large currents are distributed through the printed con-
ductive traces of an epoxy motherboard, undesirable effects
i -3-
,, I
~gl~8
may result due to the normally negligible resistance of the
printed traces. For example, if there is a need to deliver
a current of 300 amps at a power supply voltage of 2 volts
through printed circuit board traces having a resistance of,
typically, one milliohm, a voltage drop will occur in accord-
ance with the formula: V=IR; which yields a drop of 0.30 volts.
This 15% decrease in power supply voltage is an unacceptable
design practice for providing a supply voltage which will relia-
bly power the components on the daughterboard. Of course, any-
time a conductor is carrying a substantial amount of current
there is resistance heating and the conductor must be able to
carry the required current without burning up.
Prior to the development of glass-filled epoxy printed
circuit interconnecting backpanels, discrete connectors were
often mounted on a relatively thich 50-60 mils metal current dis-
' tribution plate. This was sometimes done by drilling rows of ~ -
; ..
enlarged apertures in the plate to receive the contact tails
extending from each discrete connector. Prior to placing a -
-.
connector in position on a metal voltage plate, each contact
tail was threaded onto either a conductive hub, if the particu-
lar contact was to electrically interconnect with the metal
plate voltage; or insulative hub, if the partlcular contact
1 was to be a ground or signal contact. Although such metal
'~ plate backpanel systems could distribute large amounts of cur~
r, rent through the plate with very little IR drop, each inter-
connection between signal contacts had to be individually wired,
a techni~ue much more expensive and less reliable than printed
, circuit interconnecting backpanels. Prior art metal plate
systems have inherently had a certain amount of contact res-
l~30 istance loss since each contact to be electrically connected
to a plate is first inserted into a metal hub, introducing a
certain amount of surface contact resistance, and then the
- hub is inserted into a hole in the plate, introducing addition-
al contact resistance. In the present invention, contact
-4-
1(~ 8
resistance is lowered by press fitting contacts directly into
bare metal holes in the current carrying plate. The present
invention is concerned generally with incorporating the current
carrying abilities of a metal plate system into a multi-layer
printed circuit assembly.
A multi-layer assembly and method of manufacture in which
at least one printed circuit board and at least one metal current
carrying metal plate, all having aligned holes therein, are se-
lectively interconnected with one another and bonded together
~: by contacts press fitted through the aligned holes. More partic-
ularly, the invention involves the resulting product and a meth-
od for manufacturing a multi-layer printed circuit board from
a plurality of individual printed circuit boards including
glass-filled epoxy sheets having a pattern of conductive material
upon at least one surface thereof and plated holes in the boards
extending through and electrically connected with portions of
the conductive patterns. A conductive metal plate having en-
larged clearance holes selectively placed therein is coated
with a layer in insulative dielectric material and then p~for-
ated with smaller selectively placed connecting holes. The
boards and the plate are stacked to axially align the desired
holes. A conductive contact is press fitted through the aligned
plated through holes in the upper and lower printed circuit
boards to make electrical contact with the conductive patterns
adjacent the holes on the boards and to frictionally engage the
walls of the holes to mechanically join the individual boards
into a single, unitary multi-layer printed circuit board assem-
bly. Each conductive contact passes through either an insula-
;~ tion coated, enlarged clearance hole in the plate, and is there-
by insulated therefrom, or interferingly through a smaller con-
~3Q necting hole having bare metal insides for electrical connection
therewith.
: .
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b ~
~0~91(~8
For a more complete understanding of the present invention
and for further objects and advantages thereof, reference may
now be had to the following description taken in conjunction
i with the accompanying drawings, in which:
FIGURE 1 is an exploded perspective view of one embodiment
~ of a multi-layer printed circuit board assembly havlng voltage
fi and ground plates therein and constructed in accordance with the
present invention;
' FIGURE 2 is a perspective view of the assembled multi- :
layer printed circuit board shown in FIGURE l;
FIGURE 3 is a fragmentary side view of the multi-layer ~ :
printed circuit board assembly of FIGU~E 2, illustrating four
different voltage plates in a single composite multi-layer board
constructed in accordance with one aspect of the invention:
FIGURES 4A, 4B, and 4C are fragmentary cross-section
views taken at different locations along line 4-4 of FIGURE 2
` in order to illustrate different interconnection relationships ~.
' between a contact, the printed circuit boards and the voltage
:,
` and ground plates;
FIGURE S is an exploded perspective view of another
~ embodiment of a multi-layer printed circuit board assembly,j ~ having voltage and ground plates therein and constructed in
accordance with the invention;
FIGURE 6 is a perspective view of the multi-layer printed :
circuit board assembly of FIGURE 5; -
FIGURES 7A, 7B and 7C are fragmentary cross-section views
; taken at different locations along line 7-7 of FIGURE 6 in
order to illustrate different interconnection relationships
,. :
~ between a contact, the printed circuit baords and the voltage
f~ 30 and ground plates;
FIGURES 8A, 8B and 8C and illustrative frasmentary cross-
section views illustrating different interconnection relation-
ships between a contact, the printed circuit boards and the
f: -6-
~1 ~
10~9~08
voltage and ground plates in a two-board system of the same
embodiment of the invention as shown in FIGURES 4A-4C with a
three-board system;
FIGVRE 9 is a fragmentary top plan view of a current
distribution plate employed in the present inventlon illustrat-
ing alignment holes, clearance holes and connecting holes there-
in;
FIGURE 10 is an exploded perspective view of a further
alternate embodiment of a multi-layer printed circuit board
assembly having a metal plate thereon;
FIGURE 11 is a perspective view of the assembled multi-
layer structure shown in FIGURE 10;
FIGURE 12 is a cross-section view taken about the line
12-12 of FIGURE 11; and
FIGURE 13 is a cross-section view of an embodiment of the
invention employing a current carrying metal plate and a con-
ventional laminated multi-layer printed circuit board.
A present practice in the packaging of complex electronic
circuitry is to mount, both active and passive components on
printed circuit cards, referred to as daughterboards. Each ~ ;
printed circuit board comprises a sheet of insulative material,
such as a glass-filled epoxy resin referred to as G-10 or FR-4,
having a pattern o conductive material deposited on either one
or both faces thereof. In a double-sided board, interconnections
between selected parts of the circuitry on one surface of the
board are made with circuitry on the opposite surface by plated-
through holes which form electrically continuous paths between
~; the two surfaces. The pattern of conductive material on each
board interconnects the various components mounted on the
board and provides for external power and signal connections
~;~ by conductive regions which are spaced from one another along
one edge of the board.
-7-
~:
; .
~01~9108
~' :
Printed circuit board edge connectors are devices which include
a plurality of rigidly mounted, laterally spaced, bowed contacts and a
means for guiding the board into the connector so that each of the conduc-
tive regions spaced along the edge of the board electrically engage one
contact. An example of a printed circuit board edge connector is shown in
United States Patent No. 3,671,917 issued June 20, 1972 to Ammon et al
and assigned to the assignee of the present invention.
In most electronic systems it is necessary to interconnect the
circuit patterns on the surfaces of a plurality of different printed
circuit boards. With each daughterboard inserted into an edge connector,
interconnection can be made by wiring from the tail of each individual
connector contact to the tail of each different contact with which the `~
point is to make electrical connection. In such "hard wired" interconnec~
tion systems, power can be delivered to the components by mounting the
connectors on a current carrying conductive metal backplane and insulating
each connector contact to have a wired interconnection from the metal plate.
The current trend in electronic packaging, however, is to mount
each of the connectors on a large multi-layer printed circuît board, known
as a motherhoard or a printed circuit interconnecting backpanel. Vast
numbers of the previously hard wired interconnections can be eliminated ~-
ky forming the signal interconnections between connector contacts as part
of the printed pattern on one or more surfaces of multi-layer backpanel. ~ -
Power connections to the daughterboards can similarly be made, in most
instances, by either hard wiring to the proper connector contacts or through
the printed circuitry in the motherboard. Such an interconnecting back- '
panel for card edge connectors is shown and claimed in above mentioned
~nited States Patent No. 3,660,726.
,`~
.~, .
9108
However, for certain applications where the power
requirements are high and the voltage deviation tolerances are
low, it is di~ficult to deliver adequate power to the circuitry
through the printed circuitry on the motherboard. One of the
objects of the present invention is to incorporate full power
delivery capability into a relatively inexpensive multi-layer
interconnecting backpanel. Another object of the invention
is to incorporate one or more metal plates into a printed cir-
cuit board assembly to serve as an r.f. shield for signals
carried by printed traces on the circuit boards.
~i Referring to FIGURE 1 there is shown an exploded per-
; spective view of a multi-layer printed circuit board 10 con-
~, structed in accordance with one embodiment of the invention
and having a card edge connector insulator 11 mounted thereon.
The nearer end portion 12 of the insulator 11 has been re-
moved to better illustrate the contact portions within. The
multi-layer structure of the present invention comprises a
plurality of conventional printed circuit boards 13, 14 and
~, 15 (13-15), which may be either single or double sided. Each
of the boards 13-15 include a sheet of insulative material 16,
such as a glass-filled epoxy resin known as G-10 or FR-4,
having formed thereon a pattern comprising a plurality of
.~
conductive pathways 17. Enlarged pads 18 are formed at lo-
cations on the boards 13-15 which are designed to electrical-
ly connect with other points within the multi-layer array.
In a doublesided board, one of the pads 18 surrounds a hole
19 passing through the board and on the opposite side of the
hole is a matching pad 21. Each one of the holes 19 surrounded
by the pads 18 and 21 is preferably plated with a base layer of
~30 a conductive metal, such as lead material so that pads 18 and
21 are ~oined by a contlnuous metal layer forming the walls
of the plated-through hole. The inside diameter of a plated
hole may be typically on the order of about 40 mils in diameterO
.~, _ g _
~, ' ., ., , - , . . . '
lQ1~9~8
Still referring to FIGURE 1, each one of the individual
boards 13-15 is manufactured as a single printed circuit board
and is initially drilled before plating so that the holes in
the different boards having pads to be interconnected will be
in axial alignment with one another when the boards are stacked
in the multi-layer configuration. Registration of the holes
may be easily accomplished by drilling all of the boards
simultaneously on a jig or by using alignment holes (not
shown) and precision drilling equipment so that all the holes
in successively drilled boards are accurately positioned.
As shown in FIGURE 1, each one of the individual printed
circuit boards 13-15 are separated by a current carrying
metal plate. Lying between the upper board 13 and the center
board 14 is a voltage plate 22 and lying between the center
board 14 and the lower board 15 is a ground plate 23. Each
of the plates 22 and 23 include alignment holes 24 (FIG.9), ;~
clearance holes 25 connecting holes 26. -~ -
The holes 25 and 26 in the current carrying plates 22
and 23 are preferably drilled or punched using the alignment
holes 24 as a reference point. Thus, there is a hole, either ~ -~
~ . . ,
a clearance hole 25 or a connecting hole 26, in axial alignment ~
with each of the plated holes 19 in each of the printed cir- ;
cuit boards 13-15.
Each one of the plates 22 and 23 is preferabLy on the
order of 25 mils thick and is first drilled with clearance ;~
holes 25 in the desired locations. The drilled plates are
then coated with a layer of insulation 27 over all exposed
~`; surfaces of the plate, including the inner walls of the clear- -
ance holes. The insulative coating 27 may comprise teflon, ~- -
ployurethane, polyvinylchloride or a like plastic insulator -
with good dielectric properties, i.e., preferably with a
breakdown voltage in excess of 500 volts. The thickness
of the coating 27 is preferably in the range of 5-7 mils to .
-10- . ,,
, ~
~0~9108
ensure good insulation properties. The coating 27 may be applied
to the plates by spraying, immersion or any other acceptable
means of application that will yield a coating of generally
uniform thickness and assure coverage of the inside walls of
the clearance holes 25.
After application of the insulative coating 27 to the
'' plates 22 and 23, they are again drilled in preselected locations
to produce the connecting holes 26. Connecting holes 26 may
be typically on the order of about 40 mils in diameter, i.e.,
approximately the same as the inside diameter of one of the
plated holes 19 in the boards 13-15. Since the connecting
holes 26 are drilled after the application of the insulative
coating 27 to the plate, the insides of the connecting holes
26 will comprise bare metal.
Many prior art metal backpanels have used aluminum plates:
however, in these prior applications contacts were first fitted
into hubs or grommets and then the hubs, having vertical ser-
rations therein, inserted into apertures in the panels. For
contacts made of standard material, such as a phos-bronze,
aluminum has been shown to be too soft for receiving directly -~
~ press fitted contacts. Moreover, if the metal of the plate
,~ used in the present inv~ntion is too soft, then a press fitted
contact pushed metal ou'c of the receiving hole, and deforms
it with little memory; if the metal of the plate is too hard,
then the metal of the contact will shear off or be deformed ~-
(i.e., coined). For example, it has been found that a material
having the characteristics of annealed nickel silver or an- ~
nealed cupro-nickel CDA 725 with a Rockwell Hardness of about ~ -
85 on the F scale works satisfactorily as a material for forming
the plates 22 and 23 when used with standard phos-bronze con-
tacts.
As the boards and plates, shown exploded in FIGURE 2,
are brought together into a stack, the plated-through holes
,~
-11-
~ ,, ~........
``` 1t)89108
19 in the pads 18 and 21 on each of the boards 13-15 are in
axial alignment with one another and with either a clearance
hole 25 or a connecting hole 26 in each of the metal plates
22 and 23. It should be understood that certain ones of the
holes 19 in the individual single layer boards 13-15 may not
be aligned with holes on any other boards or plates but be
buried within the stack and serve only to interconnect cir-
cuitry from the upper to the lower surface of that one board.
When the boards 13-15 and the metal plates 22 and 23 are ~ '
stacked together with proper holes in the various elements in -~
axial alignment, conductive metal contacts 31 are press fitted
down through the axially aligned holes. Each metal contact
31 comprises a bowed connector portion 32 and a tail portion ~-
33 which are separated by a shoulder 34 and an enlarged shank
~ section 35 which is greater in width than the tail. A flange -
!~ portion 36 is located at the upper end of each contact. The
plated-through holes 19 in the boards 13-15 and the connect- `;~ ,
ing holes 26 in the plates 22 and 23 are slightly larger than `~
the tail portion 33 so that a contact 31 will pass readily
into the holes. The shank section 35 is slightly larger
than the diameter of the holes 19 and 26, which may typically
be on the order of 40 mils in diameter, so that when a con-
tact is press fitted down into the holes there is a snug i
; frictional engagement between the edges 35a of the shank sec- :
tion and the metal interior of the holes 19 and 26. In the ; -:
1 ~ . ::: .
contact embodiment shown, the rectangular cross-section may
be typically on the order of 25 mils by 40 mils, producing a
~` diagonal dimension of about 44 mils. Because of the size - -
difference between the shank section 35 and the inner walls ```-
of the holes 19 and 26, the material is deformed away from
the angular edges 35a to form a tight fit between the con-
;
tiguous parts. Each of the contacts 31 shown in FIGURE 1 -
include shank sections 35 having a rectangular cross-section
-12-
10~91~t3
defining four angular edges ~5a. The tail portion 33 of each
contact 31 is substantially square in cross-section as is re-
quired to permit wiring termination by æuch techniques as wire
wrapping.
- The embodiment of the present invention shown in FIGURE 1
is illustrated as an interconnecting backpanel for a printed
circuit card edge connector such as is shown in U.S. Patent No.
3,671,917 issued June 20, 1972 to Ammon et al. It should be
I understood that the contacts used in the present invention could
' be those protruding from the bottom of a discrete connector,
as long as the press fitting shank portions thereof were long
enough. Moreover, an interfering square poSt contact without a
connecting portion on either end could be used in forming the
assembly of the present invention.
, ll Once the contacts 31 are fully inserted into the stack of
¦ boards and panels (as shown in FIG~RE 2) the insulative housing
11 is placed over the protruding connecting portions 32. The
, ¦ housing 11 is preferably formed of a moldable insulative mater-
'~ ial such as nylon or other plastic and includes an outer shell
41 which is open at its bottom portion to allow the shell to fit
down over and receive the contacts 31. The shell 41 is partially
, closed at the top by two U-shaped sections 42 at the upper
~` : portion to define a top opening 43 through which a printed cir-
cuit daughterboard edge can be inserted to engage the contacts
31. The housing 11 is preferably divided into a plurality of
contact pair receiving chambers 44 by transverse wall sections
45. Each of the chambers 44 preferably receives a pair of con-
tacts 31 when the housing 11 is placed down over the contacts.
~ The housing 11 may be held in position by frictional engage-
j 30 ment between certain contact shoulders 34 and a slot 47 in cer-
tain of the transverse walls 45. An overhanging lip portion 46
is formed on the innermost part of the U-shaped edge sections 42
to contact the flanges 36 and preload each of the contacts 31.
¦ It should, of course, be apparent that the multi-layer
printed circuit board of the present invention could be made with
10~108
contacts having a different upper portion than the card edge
contacts shown herein, and further, if other types card edge con-
tacts are used, insulative housings of different types could be
employed. Further, any contacts used could have the tail portion
` removed either before or after press fitting.
Referring back again to FIGURE 1, only one pair of contacts
31 are shown for illustrative purposes but, of course, a plural-
ity of pairs of contacts would be installed, one in each of the
, l plated holes 19 in the upper printed circuit board 13. Contacts
1 ..
l¦ are preferably installed in rows in accordance with the teachings
of U.S. Patent No. 3,676,926, issued July 18, 1972 to Kendall,
assigned to the assignee of the present invention.
When the boards 13-15 and the metal plates 22 and 23 are
brought into an aligned stac~ and the contacts 31 are press fitted
, I down through the aligned apertures 19, 25 and 26, the frictional
'~ I en~agement between the contact shank 35 and the insides of the
plated holes 19 in the upper and lower boards 13 and 15 will
mechanically join the individual layers into a single, unitary
multi-layer printed circuit board. For this reason it is pre-
/ 20 ¦ ferred to use printed circuit board material on the order of at
~i least 1/32" or 1/16" of one inch thick for the top and bottom
`~ boards 13 and 15. To a certain extent, the frictional engage-
ment of the contact shank 35 with the inner walls of the con-
necting holes 26 will also assist in mechanically joining the
layers into a single unitary structure. The metallic inner walls
of each of the plated holes 19 and the connecting holes 26 through
which an individual contact is press fitted will be electrically
¦ interconnected with one another so that the potential thereof
¦ will be the same as that of the plate through which the connecting
T hole 26 is formed. Each contact will be electrically isolated
from a clearance hole 25 in a plate through which the contact
passes by both an air gap, due to the larger size of the clear-
¦ ance hole, e.g., on the order of about 85 mils, and by the
~, I
I
~f; ~ 1,
:10~91~8
several mil thick insulative coating 27 on the interior of each
clearance hole 25. Similarly, each of the plates 22 and 23 are
electrically isolated from the circuitry patterns 17 on any print-
ed circuit board surface lying adjacent the plate by the coating
of insulating previously placed thereon as described above.
During assembly of the structure shown in FIGURE 1, the
shank portion 35 of the left contact passes interferingly
through a plated hole 19 in the top board 13; passes interfering-
ly through the plated hole 19 in the center board 14, the con-
necting hole 26 in the plate 23 and the plated hole 19 in the
bottom board 15. Thus, all points in conductive contact with the
plated holes 19, through which the left contact extends, will be
at the same electrical potential as that of the plate 23 and
electrically isolated from the potential of plate 22.
Similarly, during assembly, the shank portion 35 of theright contact passes interferingly through the plate hole 19 in
the top board, the connecting hole 26 in the plate 22, the plated
hole 19 in the center board 14; passes with clearance through the
clearance hole 25 in the plate 23; and passes interferingly
~20 through the plated hole 19 in the bottom board 15. Thus, all
~¦ points in conductive contact with the plated holes 19, through
which the right contact extends, will be at the same electrical
; potential as that of the plate 22 and electrically isolated from
1 the potential of the plate 23.
f Either the left or the right contact could be modified into
a variable signal carrying contact by converting both of the
holes in the metal plates 22 and 23, through which the contact
passes, into clearance holes. Thus, only the plated holes 19
~ through which the contact interferingly passed would be electric-
f' 30 ally interconnected.
FIGURE 2 shows the multi-layer structure of FIGURE 1 after
a plurality of pairs of the contacts 31 have been fully press
fitted into each of the aligned holes in the stack of layers
-15-
~:;
~a~s~
and the unsulative housing 11 has been laid over to form a
printed circuit card edge connector system.
Assuming for the moment that the potential of the metal
current carrying plate 23 is fixed at ground (by external power
supply connections not shown), then the potential of the other
plate 22 would be fixed at some different power supply voltage
Vcc. In this connection, another aspect of the invention is shown
in FIGURE 3. There a side view illustrates a single continuous
ground potential plate 23 into which any contacts to be supplied
with Gnd are connected by connecting hole as described above.
However, FIGURE 3 shows that, instead of a single continuous vol-
tage plate 22 held at Vcc, the plate may comprise strips 22a, 22b,
~ 22c and 22d which are electrically isolated from one another by
i~ means of both the insulative coating on each and an air gap 51
located between adjacent ones of the strips. Thus, the multi-
layer assembly of the present invention provides for a number ; -
of different power supply voltages Vccl, Vcc2, Vcc3 and Vcc4
(one associated with each one sf the strips 22a-22d) being
available to each connector. ;
FIGURES 4A, 4B and 4C are cross-section views each illus-
trating a possible interconnection pattern between a contact shank
35 and the different components of the multi-layer structure of -~
FIGURE 1. FIGURE 4A shows a signal contact shank 35 passing in-
1 ~ -
terferingly through three aligned plated holes 19 in the boards
13-15 and being isolated from a fixed potential by passing through
clearance holes 25 in each of the plates 22 and 23. Again as-
suming that the plate 22 is fixed at a voltage Vcc, and the plate
23 is fixed at a ground potential Gnd, FIGURE 4B shows a voltage
contact shank 35 passing interferingly through three aligned
plated holes 19 in the boards 13-15; being connected to Vcc by
passing interferingly through a connecting hole 26 in the voltage
plate 22; and being isolated from Gnd by passing through the clear-
ance hole 25 in the ground plate 23. Similarly, FIGURE 4C shows
~ . ,
,.. .
~ -16-
i
9108
a ground contact shank 35 passing interferingly through three
aligned plated holes 19 in the boards 13-15; being isolated from
Vcc by passing through the clearance hole 25 in the voltage plate
t 22; and being connected to Gnd by passing interferingly through
' the connecting hole 26 in the ground plate 23.
,*
FIGURE 5 shows an exploded perspective view of a different
embodiment of the invention. Identical numbers have been used
i 1 for parts which correspond to those previously numbered and des-
cribed above in connection with FIGURE 1. FIGURE 5 shows a stack
l, of elements including a top printed circuit board 13 having pat-
terns of conductive areas 17 printed thereon. Also shown are a
¦~ pair of rows of plated-through holes 19 each one of which is sur-
rounded on one surface by an upper pad 18 and on the other surface
by a lower pad 21. Pairs of contacts 31, identical to the one
¦ illustrated, are inserted into each of the pairs of plated-
through holes 19 shown in the top printed circuit board 13. Be-
tween the top printed circuit board 13 and the bottom printed cir-
cuit board 15, there are located a pair of current carrying metal
plates 22 and 23. Each of the plates 22 and 23 is drilled in cer-
tain locations with clearance holes 25, on the order of about 85
i mils in diameter, and in other locations with connecting holes
26, on the order of about 40 mils in diameter. Adjacent to each
surface of each of the metal plates 22 and 23 there is located a
;~ sheet of insulative material 61, such as a polyester film sold
~¦~ under the trademark "MYLAR" preferably in the range of 3-7 miles
¦ in thickness.
¦ When all of the contacts 31 have been press fitted down
through aligned apertures in the printed circuit boards 13 and
15 and the plates 22 and 23, and an insulative housing 11 laid
over, the finished assembly will appear as illustrated in FIGURE
6. Each contact shank portion 35 will be in electrical contact
¦ with either one or neither of the metal plates 22 and 23. Each
one of the plates 22 and 23 will be electrically isolated from
¦ one another and from conductive circuitry 17 on a contiguous
'~"
,~,.
9108
printed circuit board by the interleaved sheets of insulative
material 61. Each contact shank portion 35 which passes through
a clearance hole 25 in a metal plate will be isolated there-
from by the air gap between the inner surface of the clearance
hole through the metal plate.
For example, and again assuming plate 22 is a voltage plane
and plate 23 is a ground plane, FIGURES 7A, 7B and 7C are cross-
section views each illustrating a possible interconnection pat-
tern between a contact shank 35 and the different components of
the multi-layer structure of FIGURE 1. FIGURE 7A shows a signal
contact shank 35 passing interferingly through two aligned plated -
holes 19 in the boards 13 and 15 and being isolated from both
ground and voltage potentials by passing through clearance holes
25 in each of the plates 22 and 23. FIGURE 7B shows a voltage
contact shank 35 passing interferingly through the two aligned -
plated holes 19 in the boards 13 and 15; being connected to a ~-
Vcc by passing interferingly through a connecting hole 26 in the
voltage plate 22; and being isolated from Gnd by passing through
the clearance hole 25 in the ground potential plate 23. FIGURE
7C shows a ground contact shank 35 passing interferingly through
the two plated holes in the boards 13 and 15; being isolated from
Vcc by passing through the clearance hole 25 in the voltage plate
22; and being connected to Gnd by passing interferingly through
. ~.
?'~ the connecting hole in the ground plate 23.
Returning again to the preferred embodiment of the invention
shown in FIGURES 1-4, it will be seen that there is shown a multi-
layer structure comprising three printed circuit boards 13, 14
and 15 and two metal Plates 22 and 23, i.e., the two metal Plates
22 and 23 are separated bY the center printed circuit board 14.
It should be noted, however. that tha sYstem of the invention
will oPerate properly in a two-Printed circuit board/two-metal
plate configuration. That is, the insulative coating 27 applied
-18-
.:, f
)8
to both of the metal plates 22 and 23 will allow them to be
Positioned adjacent one another with their contiquous surfaces
in contact.
FIGURES 8A-8C, is analoqous to FIGURES 4A-4C, and are shown
merely to illustrate the possible interconnection patterns between
a contact shank 35 and the different components of a two board/
two plate system of the type shown in FIGURES 1-4. If we again
assume that the upper plate 22 is a voltage plane and the lower
plate 23 is a ~round plane, FIGURE 8A represents a signal contact
shank 35 passing interferingly through the two plate holes 19 in
the boards 13 and 15 and being isolated frvm a fixed potential
by passing through the clearance holes 25 in the plates 22 and
23. The two metal plates 22 and 23 are isolated from one an-
other by the insulative dielectric coatings 27 on each one of the
plates. FIGURE 8B represents a voltage contact shank 35 passing
interferingly through the two aligned plated holes 19 in the top
and bottom boards 13 and 15; being connected to Vcc by passing
interferingly through a connecting hole 26 in the voltage plate ;
22; and being isolated from Gnd by passing through the clearance
25 in the ground plate 23. FIGURE 8C represents a ground con- ~-
'i tact shank 35 passing interferingly through the two plated -
holes 19 in the top and bottom boards 13 and 15; being isolated
from Vcc by passing through the clearance hole 25 in the voltage
plate 22; and being connected to Gnd by passing interferingly
,~ through the connecting hole 26 in the ground plate 23. -~
3 ~ FIGURE 9 is a fragmentary top plan view of one of the métal
current carrying plates 71 used in connection with the invention.
FIGURE 9 illustrates the use of three different type holes in `
the plate 71, i.e., alignment and registration holes 24, clear-
ance holes 25 and connecting holes 26. It should also be noted
that the connecting holes 26 will act as alignment holes and -
; serve to hold the plates in proper alignment with the printed
, . .
circuit boards a~ter contacts have been press fitted therein.
,
-19-
10~9108
Referring to FIGURE 10, there is shown another illustrative
alternate embodiment of the invention which comprises a stack in-
cluding a printed circuit board 13, having traces 17 thereon; an
optional intermediate layer of insulative material 61; and an up- ~
per current carrying plate 22. A plurality of rows of plated- ~;
through holes 19, surrounded top and bottom by pads 18 and 21.
As described above, the metal plate 22 is preferably first drilled
with clearance holes 25, covered with a coating of insulation 27,
:.:: . .
and then drilled for connecting holes 26. '~
A pair of rows of contacts 31, having press fitting shank
portions 35, and shoulder portions 34, are inserted down through
both the clearance holes 25 and the connecting holes 26 into the
plated holes 19 in the board 13. '~
As shown in FIGURE 11, the insulative shell 41 is then
placed down over th,e contacts 31 and held thereon by friction-
al engagement between certain contact shoulders 34 and slots 47
in certain ones of the transverse walls 45. In this configura-
tion, i.e., with the metal plate 22 forming the top layer of the ,'~"
assembly, the forces holding the insulator to the contacts also
- . ~
'` 20 assist in holding the plate to the underlying layers, such as the `~ ,~- ~ printed circuit board 13. Thus, a discrete connector, having
~'~' press fitting contact portions extending from the bottom of the
insulator, can be used to form a multi-layer assembly and hold a
'~ top-mounted metal plate in position. Of course, the insulator '
,~ could not be removed from such a discrete connector to repair any
i damaged contacts.
;~i FIGURE 12 is a cross section view taken about the line 12-12
of FIGURE 11 and illustrates how the left contact of the pair
shown is isolated from the plate 22 by passing through the clear-
, ~ ~
~ 30 ance hole 25. The right contact, on the other hand, is electric-
r.~., .
i. .0
ally connected to the plate 22 by passing interferingly through '~
~, the connecting hole 26.
, ~ ~ ,
-20-
lV8
The technique of holding the current carrying metal plate
by a connector insulator might also be used with a conventional
multi-layer printed circuit board. For example, in FIGURE 13
there is shown a conventional multi-layer printed circuit board
which has been formed by temperature and pressure lamination tech-
niques. The holes therein are formed and plated after lamination
so that there is a continuous wall of metal extending form the
upper to the lower surface of the board. As in certain other em-
bodiments of the invention, an insulation coated metal plate
overlies the upper surface of the board with connect.ing holes in
alignment with certain plated holes and clearance holes in align-
ment with others. A contact is press fitted through the aligned -
holes and an insulator laid over. Electrical interconnection
between plated holes in the board and the metal plate is accom-
plished in the same fashion as previously described embodiments.
If the current carrying metal plate were affixed to the bottom
of a printed circuit board assembly, it could be held securely
in place by means such as bolts or rivits.
Having described the invention in connection with certain
~;~20 specific embodiments thereof, it is to be understood that fur-
ther modifications may now suggest themselves to those skilled ;
in the art and it is intended to cover such modifications as ~ ~
fall within the scope of the appended claims. ~ -
~ ~.
-21-
:,
