Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
Method for encapsulating semiconductor components mounted
on a carrier tape
The present invention concerns a method in accordance with
the preamble of claim l for encapsulating semiconductor
components mounted on a carrier tape.
Owing to an increased packaging density in electronics,
owing to defects noteced in wire-bonded components encapsu-
lated by ~eans of a polymer, and owing to the requirements
on automation, a carrier-tape technique known per se (Tape
Automated Bonding) has been developed. Normally, in the met-
hods for automatic setting and handling of components,
unprotected semiccnductor components mounted on a carrier
tape are used. The unprotected components are subject to en-
viromental effects and mechanical damage in connection with
the handling of the components or of the products including
components. This is why it is necessary to encapsulate the
semiconductor components on the tape so that the tape and
the components can be used in automatic machines, just like
uncapsulated components can.
In the methods of protection of carrier-tape components
known in prior art, only the face of the semiconductor piece
is protected, as disclosed, e.g., in the publication GB A
2,009,504 (H 01 L 21/94), or the semiconductor piece and the
conductors extending frorn same are protected, so that the
component is difficult to handle in automatic setting
machines.
It is an object of the present invention to provide a more
practical method for the encapsulation of components mounted
on a tape.
The invention is based on the idea that each component and
the conductors extending from the component are protected by
means of the encapsulation polymer up to a desired distance
~ ~Sd ~
from the component. In the method, the polymer is spread by
means of a dispenser device onto the semiconductor
componentr The spreading of the encapsulation pol~ner beyond
the desired area is prevented by using agents that reduce
the surface energy, and an encapsulation tape.
In the method in accordance with the present invention, the
spreading of the encapsulating polymer is limited in a cont-
rol~ed way. The components encapsulated in accordance with
the method are easy to handle, because the encapsulating po-
lymer does not contaminate th~ support area functioning as
an aligning and handling plane while, however, protecting
the conductors extending from it towards the component,
which is a great advantage owing to the protection from
moisture offered thereby, in particular in the case of high-
voltage components. Components encapsulated by means of this
method can be used in the same way as surface connection
components after the connecting conductors of the component
have been bent.
The use of a fluoropolymer of low surface ener~y in order to
limit the spreading of the encapsulating polymer is known
per se, e.g., from the publication SE B 11 401,056 (H 01 L
21/56), wherein it is used in the drop protection of a semi-
conductor wire-connected onto a substrate. In the present
invention, the large moistening angle due to the low surface
energy, and a suitable encapsulating tape have been applied
for the preparation of an encapsulation of specified shape
and dimension for carrier-tape components before their
connection to the component plate.
More specifically, the method in accordance with the inven-
tion is characterized by what is stated in the character-
izing part of claim 1.
By means of the method in accordance with the invention, it
is possible to prevent access of moisture into the component
in a highly efficient manner.
The invention will be examined in the following in more de-
tail by means of the exemplifying embodiment in accordance
with the attached drawings.
Figure la shows an encapsulated component as viewed from
above.
Figure lb is sectional view of the component of Figure la,
taken along the line A-A.
Figure 2 is a sectional view of an apparatus for the
application of the polymer film limiting the spreading of
the encapsulation polymerO
Figure 3a shows a component being encapsulated, as viewed
from above.
Figure 3b is a sectional view of the component of Figure 3a,
taken along the line B-B.
Figure 4 is a sectional view of a final component.
Figure 5 shows one embodiment of the method in accordance
with the invention as an operating diagram.
By means of the encapsulating polymer coating 1, the area 19
inside the annular support area 2 of the carrier tape 6 tthe
so-called ILB area) is protected. This area 2 comprises the
TAB (Tape Automatic Bonding) component 3 and its connecting
conductors. The encapsulating method comprises nine steps Pl
to P9 (Fig. 5) as follows:
STEP 1
Into the encapsulating apparatus, a TAB or carrier tape reel
5 is inserted, the carrier tape 6 is taken off the reel, and
the carrier tape 6 is fed forwards, and the spacer tape 7 is
removed. The carrier tape 6 may be made of, eg., a polyimi-
de, a polyester, or glass fibre epoxy. The other reel 8 in
the apparatus is provided for the encapsulating tape 9. The
.
B
function of the encapsulating tape 9 is to prevent spreading
of the polymer to underneath the component 3 and the annular
suppor~ area 2. The encapsulating tape 9 moves forwards si-
multaneously with the carrier tape 6.
STEP 2
The surface energies of the support area 2 of the carrier
tape 6 and of the encapsulating tape 9 must be sufficiently
low in order that the encapsulating polymer 26, 13 should
not moisten them. This prevents spreading of the polymer 26
to underneath and onto the support area 2. The support area
2 is "stamped" from above and from underneath by means of
stamps 10, 11, whose cross-sectional shape is similar to the
shape of the annular support area 2 (Fig. 2)o By means of
the stamps 10, 11, a polymer film 24, 25 of a low surface
energy is pressed on both sides of the support area ~ (fig. 2).
The polymer to be absorbed onto the stamps 10, 11 has been
dissolved into the readily volatile solvent. The en-
capsulating tape 9 is guided through a basin 12 containing
said polymer solution 13, whereby the tape 9 becomes coated
with the polymer. Alternatively, it is possible to use a
tape whose surface energy is sufficiently low, in which case
the tape need not be coated.
STEP 3
The carrier tape 6 and the encapsulating tape 9 pass through
a warm-air blast 14, 15. In the warm-air blast 14, 15 the
solvent of the polymer used in the preceding step is evapo-
rated. The blast 14, 15 also removes any loose paticles
possibly present on the semiconductor component 3.
STEP 4
The encapsulating tape 9 is guided to underneath the carrier
tape 6 so that it is pressed evenly against the bottom of
the semiconductor piece 3. From this step up to step 8, the
encapsulating tape 9 is tightly fixed on the bottom of the
semiconductor piece 3. The encapsulating tape 9 prevents
5'~
flow of encapsulating polymer 25 to a level lower than the
bottom face level of the semiconductor piece 3 (Fig. 3b).
STEP 5
The encapsulating tape 9 and the carrier tape 6 above it are
heated in the first oven zone 16. The encapsulating polymer
26 moistens the face of the component 3 better when it is
warm.
STEP 6
The encapsulating polymer 26, eOg., epoxy, polyurethane, or
silicon, is spread first onto the face of the semiconductor
piece 3, thereupon onto the ILB area 19. The dosage of the
polymer 26 is carried out by means of a dispenser 17, and
the spreadig by shifting the dispensing tip 18 relative the
area to he protected~ Some encapsulating materials require
preheating in order that they should spread evenly onto the
face to be protected. The viscosity of the encapsulating
polymer is reduced and its moistening capacity increased if
the dispensing tip 18 or the polymer container (not shown)
is heated.
STEP 7
The encapsulating polymer 26 is hardened in the second oven
zone 20.
STEP 8
The encapsulating tape 9 is removed from underneath the en-
capsulated TAB components mounted on the carrier tape 6 onto
the reel 21. At this stage, if necessary, a hot air blast
22 is used to heat the encapsulating tape 9. On heating,
the tape 9 becomes softer, whereby it becomes detached more
readily from the encapsulating TAB components 3.
STEP 9
The carrier tape 6, provided with the encapsulating TAB com-
ponents 3, and the spacer tape 7 are passed onto the reel 23
one above the other.
