U.S. patent application number 09/809781 was filed with the patent office on 2002-09-19 for semiconductor card and method of fabrication.
Invention is credited to Bolken, Todd O., Corisis, David J..
Application Number | 20020131251 09/809781 |
Document ID | / |
Family ID | 25202202 |
Filed Date | 2002-09-19 |
United States Patent
Application |
20020131251 |
Kind Code |
A1 |
Corisis, David J. ; et
al. |
September 19, 2002 |
SEMICONDUCTOR CARD AND METHOD OF FABRICATION
Abstract
A semiconductor card includes a printed circuit substrate and
one or more semiconductor components, such as dice or packages,
mounted to the substrate. The substrate is initially a segment of a
strip containing several substrates. The substrate is defined by a
peripheral opening in the strip, and is connected to the strip by
connecting segments. The card also includes a plastic body molded
to the substrate and having notches that initially align with the
connecting segments. The notches provide access for severing the
connecting segments, and also enclose any slivers of substrate
material resulting from severing of the connecting segments. A
method for fabricating the package includes the steps of providing
the strip, and providing a molding apparatus configured to mold the
plastic body to the substrate. The molding apparatus includes pins
configured to contact the connecting segments to form the notches.
A system for performing the method includes the strip, the molding
apparatus and a punch apparatus for severing the connecting
segments.
Inventors: |
Corisis, David J.;
(Meridian, ID) ; Bolken, Todd O.; (Meridian,
ID) |
Correspondence
Address: |
STEPHEN A GRATTON
THE LAW OFFICE OF STEVE GRATTON
2764 SOUTH BRAUN WAY
LAKEWOOD
CO
80228
|
Family ID: |
25202202 |
Appl. No.: |
09/809781 |
Filed: |
March 16, 2001 |
Current U.S.
Class: |
361/760 |
Current CPC
Class: |
H01L 2924/181 20130101;
H01L 2224/49175 20130101; G06K 19/077 20130101; H05K 5/065
20130101; H01L 2224/05554 20130101; H05K 5/026 20130101; H01L
2924/181 20130101; H01L 2224/49171 20130101; H01L 2924/00012
20130101 |
Class at
Publication: |
361/760 |
International
Class: |
H05K 007/02; H05K
007/06 |
Claims
What is claimed is:
1. A semiconductor card comprising: a printed circuit substrate
having a circuit side, a back side and a peripheral edge, the
substrate comprising a plurality of conductors on the circuit side
and a plurality of external contacts on the back side in electrical
communication with the conductors; at least one semiconductor
component on the circuit side in electrical communication with the
conductors; and a plastic body molded to the circuit side and to
the peripheral edge, the plastic body covering the semiconductor
component and leaving the external contacts exposed.
2. The semiconductor card of claim 1 further comprising at least
one notch in the plastic body configured to enclose a portion of
the peripheral edge of the substrate.
3. The semiconductor card of claim 1 further comprising an
encapsulant on the circuit side encapsulating the semiconductor
component.
4. The semiconductor card of claim 1 wherein the plastic body
leaves the back side of the substrate exposed.
5. The semiconductor card of claim 1 wherein the plastic body
comprises an epoxy resin.
6. A semiconductor card comprising: a printed circuit substrate
which is initially a segment of a strip and initially connected to
the strip with a plurality of connecting segments; at least one
semiconductor component on the substrate; and a plastic body molded
to the substrate on the semiconductor component, the plastic body
comprising an edge portion and a plurality of notches in the edge
portion configured to enclose portions of the connecting segments
remaining on the substrate.
7. The semiconductor card of claim 5 wherein the substrate
comprises a peripheral edge and the plastic body is molded to the
peripheral edge.
8. The semiconductor card of claim 5 further comprising an
encapsulant on the substrate encapsulating the semiconductor
component.
9. The semiconductor card of claim 5 wherein the portions of the
connecting segments comprise at least one sliver contained in a
notch.
10. The semiconductor card of claim 5 wherein the substrate
comprises a circuit side wherein the plastic body is molded and an
exposed back side having a plurality of external contacts in
electrical communication with the semiconductor component.
11. The semiconductor card of claim 5 wherein the semiconductor
component comprises a semiconductor die wire bonded or flip chip
mounted to the substrate.
12. The semiconductor card of claim 5 wherein the semiconductor
component comprises a semiconductor package bonded to the
substrate.
13. The semiconductor card of claim 5 wherein the plastic body
comprises an epoxy resin.
14. A semiconductor card comprising: a printed circuit substrate
comprising a circuit side having a plurality of conductors thereon,
a back side having a plurality of external contacts thereon in
electrical communication with the conductors, and a peripheral
edge; at least one semiconductor component on the circuit side in
electrical communication with the conductors; and a plastic body
molded to the circuit side and peripheral edge and covering the
semiconductor component, the plastic body comprising an edge
portion and at least one notch in the edge portion configured to
enclose a selected portion of the peripheral edge such that an
outline of the card is not affected by a sliver on the selected
portion.
15. The semiconductor card of claim 14 wherein the sliver comprises
a portion of a connecting segment configured to attach the
substrate to a panel.
16. The semiconductor card of claim 14 wherein the notch has a
generally hemispherical shape.
17. The semiconductor card of claim 14 further comprising an
encapsulant on the circuit side encapsulating the semiconductor
component.
18. The semiconductor card of claim 14 wherein the semiconductor
component comprises a die wire bonded or flip chip mounted to the
substrate.
19. The semiconductor card of claim 14 wherein the semiconductor
component comprises a package having contacts bonded to the
substrate.
20. A semiconductor card comprising: a printed circuit substrate
comprising a reinforced organic polymer resin, the substrate
initially defined by a peripheral opening in a strip and attached
to the strip with a plurality of connecting segments, the substrate
having a circuit side, a back side with a plurality of external
contacts thereon, and a peripheral edge; at least one semiconductor
component on the circuit side in electrical communication with the
external contacts; and a plastic body molded to the circuit side
and to the peripheral edge and covering the semiconductor component
while leaving the back side exposed, the plastic body comprising a
plurality of notches configured to enclose portions of the
peripheral edge proximate to the connecting segments.
21. The semiconductor card of claim 20 wherein at least one portion
of the peripheral edge comprise a sliver of a connecting
segment.
22. The semiconductor card of claim 20 wherein the notches are
generally hemispherical in shape.
23. The semiconductor card of claim 20 wherein the plastic body
comprises a Novoloc epoxy resin.
24. The semiconductor card of claim 20 wherein the plastic body
comprises four notches.
25. A method for fabricating a semiconductor card comprising:
providing a strip comprising a substrate and at least one
connecting segment connecting the substrate to the strip; mounting
at least one semiconductor component to the substrate; molding a
plastic body on the substrate and over the semiconductor component;
and forming a notch in the plastic body during the molding step
configured to enclose an edge portion of the substrate proximate to
the connecting segment.
26. The method of claim 25 wherein the molding step is performed by
placing a pin in contact with the connecting segment to form the
notch.
27. The method of claim 25 wherein the substrate comprises a
circuit side and a peripheral edge and the plastic body is molded
to the circuit side and to the peripheral edge.
28. The method of claim 25 wherein the plastic body comprises an
epoxy resin.
29. The method of claim 25 wherein the substrate comprises a
reinforced organic polymer resin.
30. The method of claim 25 wherein the mounting step comprises wire
bonding or flip chip mounting the semiconductor component to the
substrate.
31. A method for fabricating a semiconductor card comprising:
providing a strip comprising a plurality of substrates, the strip
comprising a plurality of peripheral openings defining the
substrates and a plurality of connecting segments attaching the
substrates to the strip; mounting a plurality of semiconductor
components to the substrates; molding a plurality of plastic bodies
to the substrates; placing a plurality of pins on the connecting
segments during the molding step configured to form a plurality of
notches in the plastic bodies proximate to the connecting segments;
and severing the connecting segments using the notches to provide
access and to enclose portions of the connecting segments which
remain following the severing step.
32. The method of claim 31 wherein the severing step is performed
by placing cutters through the notches.
33. The method of claim 31 wherein the substrates comprise
peripheral edges and the plastic bodies are molded to the
peripheral edges.
34. The method of claim 31 further comprising encapsulating the
semiconductor components with an encapsulant and covering the
encapsulant with the plastic bodies.
35. The method of claim 31 wherein the substrates comprise circuit
sides wherein the semiconductor components are mounted and back
side which are not covered by the plastic bodies.
36. A method for fabricating a semiconductor card comprising:
providing a strip comprising a plurality of reinforced organic
polymer substrates, the strip comprising a plurality of peripheral
openings defining the substrates and a plurality of connecting
segments attaching the substrates to the strip; mounting a
plurality of semiconductor components to the substrates; providing
a molding apparatus comprising a plurality of mold cavities
containing a plurality of pins configured to contact the connecting
segments and to mold plastic bodies on the substrate having notches
aligned with the connecting segments; molding the plastic bodies to
the substrates using the molding apparatus; providing a punch
apparatus comprising a plurality of cutters configured to move
through the notches to sever the connecting segments; and severing
the connecting segments using the punch apparatus.
37. The method of claim 36 wherein the substrate comprise
peripheral edges and the notches are located proximate to the
peripheral edges and are configured to enclose portions of the
connecting segments which remain following the severing step.
38. The method of claim 36 wherein the mounting step comprises wire
bonding the semiconductor components to the substrate.
39. The method of claim 36 wherein the mounting step comprises flip
chip mounting the semiconductor components to the substrate.
40. The method of claim 36 wherein the mounting step comprises
bonding the semiconductor components to the substrate.
41. A method for fabricating a semiconductor card comprising:
providing a strip comprising a substrate and a plurality of
connecting segments connecting the substrate to the strip, the
substrate comprising a circuit side, a back side having a plurality
of external contacts and a peripheral edge; mounting at least one
semiconductor component to the circuit side in electrical
communication with the external contacts; molding a plastic body on
the circuit side comprising an edge portion on the peripheral edge;
forming a plurality of notches in the edge portion during the
molding step proximate to the peripheral edge; and severing the
connecting segments by moving cutters through the notches.
42. The method of claim 41 further comprising encapsulating the
semiconductor component prior to the molding step.
43. The method of claim 41 wherein the molding step is performed
using a mold cavity having a plurality of pins for contacting the
connecting segments.
44. The method of claim 41 wherein the plastic body comprises an
epoxy resin.
45. The method of claim 41 wherein the mounting step comprises wire
bonding, bonding or flip chip mounting the semiconductor
components.
46. A system for fabricating a semiconductor card comprising: a
strip comprising a plurality of reinforced organic polymer
substrates, the strip comprising a plurality of peripheral openings
defining the substrates and a plurality of connecting segments
attaching the substrates to the strip; and a molding apparatus
comprising a plurality of mold cavities containing a plurality of
pins configured to contact the connecting segments and to mold
plastic bodies on the substrate having notches aligned with the
connecting segments.
47. The system of claim 46 further comprising a punch apparatus
comprising a plurality of cutters configured to move through the
notches to sever the connecting segments.
48. The system of claim 46 the substrates comprise circuit sides,
back sides and peripheral edges and the molding apparatus is
configured to mold the plastic bodies to the circuit sides and to
the peripheral edges.
49. The system of claim 46 wherein the notches are configured to
enclose slivers of the connecting segments.
50. The system of claim 46 wherein the molding apparatus is
configured to mold an epoxy resin to form the plastic bodies.
Description
FIELD OF THE INVENTION
[0001] This invention relates generally to semiconductor
manufacture, and more particularly to an improved semiconductor
card, and to a method and to a system for fabricating the card.
BACKGROUND OF THE INVENTION
[0002] One type of electronic assembly containing semiconductor
components is referred to as a "card". Examples of cards include
multi media cards (MMC), memory cards, smart cards, and personal
computer memory card international association (PCMCIA) cards. The
present patent application refers to these types of cards as
"semiconductor cards". These cards are also sometimes referred to
as "daughter boards".
[0003] Typically, the card includes a printed-circuit substrate
(usually multilayer) that provides interconnection and power
distribution for semiconductor components, such as semiconductor
dice or packages, on the card. The card also provides interconnect
capability to a next level package, such as a mother
printed-circuit board. In addition to semiconductor components, the
card can include other types of electronic components such as
resistors, inductors and capacitors. Typically the components are
mounted to a circuit side of the board, and the external contacts
for the card are contained on an opposing back side of the
substrate.
[0004] In the past it has been common practice to encapsulate the
semiconductor components contained on the circuit side of the
substrate using a "glob top" encapsulant. The cards typically also
include a separate cover adhesively attached to the substrate,
which encloses all of the components on the circuit side of the
card. One shortcoming of this approach is that the cover can add
thickness to the card. For most applications it is desirable to
make the card as thin as possible. Also, the covers are typically
fabricated separately, and then attached to the substrate using an
adhesive. The cover represents a separate component which requires
additional process steps, and which is subject to detachment from
the substrate.
[0005] Besides being as thin as possible, another requirement for
these cards is that the peripheral outlines and dimensions of the
cards be as consistent as possible. A typical fabrication processes
is performed on a strip which is similar to a lead frame and
contains several printed circuit substrates. The individual cards
are then separated from the strip using a singulation step such as
sawing. Often the singulation step produces slivers, and roughened
portions on the edges of the printed-circuit substrate. These
defects can adversely affect the peripheral outline, dimensions and
appearance of the card. Specifications on the peripheral outline
and dimensions of cards, have been set by various industry standard
setting bodies (e.g., PCMCIA) Defects such as slivers of substrate
material, can make the peripheral outline of the card larger, such
that the card does not meet the specifications.
[0006] The present invention is directed to a semiconductor card in
which the components on the printed circuit substrate are
encapsulated in a molded plastic body, such that the card can be
made as thin as possible. In addition, the fabrication process
employs a strip of substrate material, and a singulation step,
designed to reduce defects, such as substrate slivers and
dimensional irregularities.
SUMMARY OF THE INVENTION
[0007] In accordance with the present invention, an improved
semiconductor card, and a method and a system for fabricating the
card are provided.
[0008] The card includes a printed circuit substrate, which
comprises an electrically insulating material, such as an organic
polymer resin reinforced with glass fibers. The substrate includes
a circuit side with a pattern of conductors thereon, a back side
with a pattern of external contacts thereon, and a plurality of
interlevel conductors which electrically connect the conductors on
the circuit side to the external contacts on the back side. The
substrate is initially a segment of a strip containing multiple
substrates. The strip is similar in function to a semiconductor
lead frame, and allows various fabrication processes to be
performed on several substrates at the same time. The substrate is
connected to the strip with connecting segments that are similar in
function to tie bars on a semiconductor lead frame. In addition, a
peripheral outline of the substrate is defined by a peripheral
opening in the strip.
[0009] The card also includes one or more semiconductor components
mounted to the circuit side of the substrate in electrical
communication with the conductors on the circuit side. The
semiconductor components can comprise bare dice wire bonded to the
conductors, bumped dice flip chip mounted to the conductors, or
semiconductor packages bonded to the conductors. The card also
includes a molded encapsulant on the circuit side of the substrate
which encapsulates the components. The card also includes a molded
plastic body which covers the encapsulant, the remainder of the
circuit side, and the edges of the substrate.
[0010] The plastic body includes one or more notches formed on edge
portions thereof in alignment with the connecting segments for the
substrate. Although most portions of the connecting segments are
removed during singulation of the substrate from the strip, some
portions of the connecting segments (e.g., slivers) can remain in
the notches following the singulation step. However, because the
notches are configured to enclose these remaining portions of the
connecting segments, the peripheral outline and dimensions of the
card can still meet specification. The notches in addition to
enclosing defects on the substrate also function to provide access
to the connecting segments for singulating the substrate from the
strip.
[0011] A method for fabricating the semiconductor card includes the
initial step of providing the strip containing multiple printed
circuit substrates. The peripheral outline of each substrate on the
strip is defined by the peripheral openings through the strip, and
each substrate is connected to the strip by the connecting
segments. In addition, the method includes the steps of mounting
the semiconductor components to the substrates on the strip, and
then encapsulating the semiconductor components.
[0012] Following the encapsulating step, a molding step is
performed to mold the plastic bodies to the substrates on the
strip. The molding step can be performed using a molding apparatus
having mold cavities configured to mold the plastic bodies to the
strips. The mold cavities include pins configured to contact the
connecting segments for the substrates, and to form the notches in
the plastic bodies in alignment with the connecting segments.
Following the molding, a singulation step is performed by severing
the connecting segments to separate the substrates from the strip.
During the singulation step, the notches provide access for
severing the connecting segments. In addition, any slivers from the
connecting segments remain in the molded notches such that the
peripheral outline of the card meets specification.
[0013] A system for performing the method includes the strip
containing multiple printed circuit substrates connected to the
strip by the connecting segments and defined by the peripheral
openings in the panel. In addition, the system includes the molding
apparatus having the mold cavities for molding the plastic bodies
to the substrates. The system also includes the pins in the molding
cavities configured to mold the notches into the plastic bodies and
to hold the connecting segments down during the molding step. The
system also includes a punch apparatus having cutters configured to
move through the notches in the plastic bodies to sever the
connecting segments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1A is an enlarged plan view of a semiconductor card
fabricated in accordance with the invention;
[0015] FIG. 1B is an enlarged bottom view of the semiconductor
card;
[0016] FIG. 1C is an enlarged side elevation view of the
semiconductor card;
[0017] FIG. 1D is an enlarged cross sectional view of the
semiconductor card, taken along section line 1D-1D of FIG. 1A;
[0018] FIG. 1E is an enlarged cross sectional view of the
semiconductor card, taken along section line 1E-1E of FIG. 1A;
[0019] FIG. 1F is an enlarged cross sectional view, equivalent to
FIG. 1E, of an alternate embodiment semiconductor card;
[0020] FIG. 1G is an enlarged cross sectional view of the
semiconductor card, taken along section line 1G-1G of FIG. 1E;
[0021] FIGS. 2A-2F are schematic cross sectional views illustrating
steps in a method for fabricating the semiconductor card in
accordance with the invention;
[0022] FIG. 3A is an enlarged schematic plan view of the
semiconductor card during fabrication, taken along line 3A-3A of
FIG. 2A;
[0023] FIG. 3B is an enlarged schematic plan view of the
semiconductor card during fabrication, taken along line 3B-3B of
FIG. 2B, and partially cut away;
[0024] FIG. 3C is an enlarged schematic plan view of the
semiconductor card during fabrication, taken along line 3C-3C of
FIG. 2C, and partially cut away;
[0025] FIG. 3D is an enlarged schematic plan view of the
semiconductor card during fabrication, taken along line 3D-3D of
FIG. 2D;
[0026] FIG. 3E is an enlarged schematic plan view of the
semiconductor card during fabrication, taken along line 3E-3E of
FIG. 2E;
[0027] FIG. 3F is an enlarged schematic plan view of the
semiconductor card during fabrication, taken along line 3F-3F of
FIG. 2F;
[0028] FIG. 4 is an enlarged cross sectional view taken along
section line 4 of FIG. 3F; and
[0029] FIG. 5 is a schematic view of a system constructed in
accordance with the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0030] Referring to FIGS. 1A-1G, a semiconductor card 10
constructed in accordance with the invention is illustrated. The
card 10 includes a printed circuit substrate 12, and a plurality of
semiconductor components 14 (FIG. 1E) mounted to the substrate 12.
The card 10 also includes an encapsulant 16 (FIG. 1E) on the
substrate 12 encapsulating the components 14, a plastic body 18
molded to the encapsulant 16 and to the substrate 12, and an array
of external contacts 20 (FIG. 1B) on the substrate 12.
[0031] The substrate 12 comprises an electrically insulating
material such as an organic polymer resin reinforced with glass
fibers. Suitable materials for the substrate 12 include
bismaleimide-triazine (BT), epoxy resins (e.g., "FR-4" and "FR-5"),
and polyimide resins. These materials can be formed with a desired
thickness, and then punched, machined, or otherwise formed with a
required peripheral configuration, and with required features. A
representative thickness of the substrate 12 can be from about 0.2
mm to 1.6 mm. As will be further explained, the substrate 12 is
initially a segment of a strip 30 (FIG. 3A) which is used to
fabricate several cards 10 at the same time.
[0032] As shown in FIG. 1B, the substrate 12 has a generally
rectangular peripheral shape but with one chamfered corner 22. The
substrate 12 includes a circuit side 24 (FIG. 1G) wherein the
semiconductor components 14 are mounted, a back side 26 (FIG. 1B)
wherein the external contacts 20 are located, and a peripheral edge
28 (FIG. 1B). As shown in FIG. 1G, the circuit side 24 of the
substrate 12 includes patterns of conductors 32 and contacts 36.
For simplicity only a few of the conductors 32 are shown. The
conductors 32 can comprise a highly conductive metal, such as
copper, and are configured to provide separate electrical paths on
the substrate 12 for the electrical components contained on the
card 10. The contacts 36 provide electrical connection points for
performing various electrical functions, such as testing the
semiconductor components 14, or other circuits and components on
the substrate 12. The substrate 12 also includes conductive vias
(not shown), or other interlevel conductors, that provide separate
electrical paths through the substrate 12 between the conductors
32, the contacts 36, the components 14, and the external contacts
20 (FIG. 1B).
[0033] In addition to the semiconductor components 14, the card
also includes various other electrical components 40 on the
substrate 12, such as resistors, capacitors and inductors in
electrical communication with the conductors 32 and with the
semiconductor components 14. The semiconductor components 14, the
conductors 32, and the electrical components 40 form a circuit 42
(FIG. 1G) on the substrate 12 that is configured to perform a
desired function (e.g., memory storage, sound production, video
production, product identification, etc.).
[0034] The external contacts 20 on the substrate 12 provide
connection points for sending signals to the circuit 42 or for
receiving signals generated by the circuit 42. The external
contacts 20 are configured for mating electrical engagement with
corresponding contacts (not shown) on a mother circuit board or
other electrical assembly (not shown). In the illustrative
embodiment the external contacts 20 comprise planar pads formed of
a non-oxidizing material such as gold. However, other
configurations for the external contacts 20 can be employed (e.g.,
bumps, pins, etc.).
[0035] As shown in FIG. 1E, the components 14 can comprise bare
semiconductor dice wire bonded to the substrate 12. In this case,
wires 44 are bonded to bond pads 62 (FIG. 1G) on the components 14,
and to corresponding bond pads 34 (FIG. 1G) on the substrate 12 in
electrical communication with the conductors 32. As also shown in
FIG. 1E, the encapsulant 16 encapsulates the components 14, the
wires 44 and the associated wire bonds as well. The encapsulant 16
can comprise a suitable curable polymer such as a "glob top"
material, an epoxy resin, or a silicone material deposited and
formed using a suitable process (e.g., molding, dispensing through
a nozzle). Depending on the encapsulant a curing step for the
encapsulant such as heating in a oven may also be required.
[0036] As an alternative to wire bonding, and as shown in FIG. 1F,
a semiconductor card 10A can include semiconductor components 14A
in the form of dice or packages flip chip mounted to a substrate
12A, or semiconductor packages (e.g., TSOPs, chip scale packages)
bonded to the substrate 12A. In either case, contacts 46A on the
components 14A, such as solder balls or C4 bumps, are bonded to
corresponding contacts on the substrate 12A. In addition, an
encapsulant 16A encapsulates the components 14A, and external
contacts 20A on the substrate 12A provide outside electrical
connection points for the card 10A. The card 10A also includes a
molded plastic body 18A substantially similar to the molded plastic
body 18 for card 10.
[0037] Referring again to FIGS. 1A and 1B, the molded plastic body
18 for card 10 completely covers the circuit side 24 of the
substrate 12. In addition, the molded plastic body 18 has a
peripheral outline that substantially matches, but is slightly
larger than the peripheral outline of the substrate 12. As will be
further explained, the molded plastic body 18 can comprise a
Novolac based epoxy formed in a desired shape using a transfer
molding process, and then cured using an oven.
[0038] As shown in FIG. 1B, the molded plastic body 18 also
includes an edge portion 52 that covers the peripheral edge 28 of
the substrate 12 but leaves the backside 26 of the substrate 12 and
the external contacts 20 exposed. In addition, as shown in FIGS. 1A
and 1D, the molded plastic body 18 includes a recessed face portion
48 configured to retain a label. The label, for example, can
comprise a preprinted sheet of paper having art work on one side,
and an adhesive on an opposing side. As also shown in FIGS. 1A and
1D, the molded plastic body 18 includes a groove 50 that functions
as a finger grip for handling the card 10.
[0039] As also shown in FIGS. 1A and 1B, the molded plastic body 18
includes notches 38 formed in the edge portion 52. In the
illustrative embodiment, the notches 38 are generally hemispherical
in shape, and extend completely through the edge portion 52 of the
molded plastic body 18. The notches 38 can also extend a short
distance into the substrate 12 such that the peripheral edge 28 of
the substrate 12 is slightly notched. In the illustrative
embodiment, there are four notches 38 consisting of two pairs
located on opposing longitudinal sides of the card 10. The notches
38 align with connecting segments 54 (FIG. 3A) of the substrate 12
that initially attach the substrate 12 to the strip 30. One
function of the notches 38 is to provide access for severing the
connecting segments 54 to singulate the substrate 12, and the card
10, from the strip 30 following the fabrication process. Another
function of the notches 38 is to provide an enclosed area for
containing rough edges of the substrate 12, or slivers of substrate
material, that may form during severing of the connecting segments
54.
[0040] Referring to FIGS. 2A-2F and 3A-3F, steps in a method for
fabricating the card 10 are illustrated. Initially as shown in
FIGS. 2A and 3A, the strip 30 containing the substrate 12, as well
as additional substrates 12 (not shown) is provided. The strip 30
can also be described as a panel similar in construction to a
semiconductor lead frame, and can include as many substrates as
desired (e.g., two to eighteen). The strip 30 facilitates the
fabrication process in that different operations, such as die
attach, wire bonding, molding and singulation can be performed at
the same time on multiple substrates 12. If desired, the strip 30
can be constructed from a commercially produced bi-material core,
such as a copper clad bismaleimide-triazine (BT) core, available
from Mitsubishi Gas Chemical Corp., Japan. A representative weight
of the copper can be from 0.5 oz to 2 oz. per square foot.
[0041] As shown in FIG. 3A, the strip 30 can include indexing
openings 56 that facilitate handling by automated equipment such as
conveyors, magazines, die attachers, wire bonders and molding
apparatus. In addition, the substrate 12 on the strip 30 can
include the conductors 32, the contacts 36 and the electrical
components 40, configured substantially as previously described, on
the circuit side 24 of the substrate 12. Similarly, the substrate
12 can include the external contacts 20 on the backside 26, and the
vias (not shown) which electrically connect the external contacts
20 to the conductors 32, to the electrical components 40 and to the
contacts 36.
[0042] The strip 30 also includes the connecting segments 54
configured to attach the substrate 12 to the strip 30. The
connecting segments 54 are similar in structure and function to tie
bars of a semiconductor lead frame. As also shown in FIG. 3A, a
peripheral opening 58 though the strip 30 defines the peripheral
outline of the substrate 12. The peripheral opening 58 is
continuous except where the connecting segments 54 are located.
[0043] Next, as shown in FIGS. 2B and 3B, the semiconductor
components 14 are mounted to the circuit side 24 of the substrate
12. Adhesive layers 60 (FIG. 2B) such as a curable adhesive (e.g.,
polyimide), or a tape material ("KAPTON" tape), can be used to
adhesively attach the semiconductor components 14 to the substrate
12. Also, a conventional die attacher can be used to perform the
attachment process.
[0044] As shown in FIG. 3B, the semiconductor components 14 can be
wire bonded to the substrate 12 by bonding the wires 44 to the bond
pads 62 on the semiconductor components 14 and to the bond pads 34
on the substrate 12. A conventional wire bonder can be used to
perform the wire bonding step. Alternately, instead of wire
bonding, a flip chip process (e.g., C4), or a TAB bonding process,
can be used to electrically connect the semiconductor components 14
to the conductors 32.
[0045] As another alternative, the semiconductor components 14A
(FIG. 1F) can include contacts 46A (FIG. 1F) such as solder balls
configured for bonding to the bond pads 34 on the substrate 12
using a solder reflow process. Alternately, the contacts 46A (FIG.
1F) can comprise conductive polymer bumps configured for bonding to
the bond pads 34 on the substrate 12 using a curing process.
[0046] As also shown in FIGS. 2B and 3B, following wire bonding,
the encapsulant 16 can be formed on the semiconductor components 14
and on portions of the substrate 12. The encapsulant 16 can
comprise a glob top material, such as an epoxy resin or silicone,
deposited using a suitable deposition process and then cured. As
another alternative the encapsulant 16 can comprise a Novolac based
epoxy formed in a desired shape using a transfer molding process,
and then cured using an oven.
[0047] Next, as shown in FIGS. 2C and 3C, the molded plastic body
18 is formed using a molding apparatus 64. The molding apparatus 64
can comprise a conventional transfer molding apparatus modified to
include pins 74 to be hereinafter described. The molding apparatus
64 includes a first plate 66 configured to contact the circuit side
24 of the substrate 12. In addition, the molding apparatus 64
includes a second plate 72 configured to contact the back side 26
of the substrate 12. If desired, the back side 26 of the substrate
12 can be protected by tape or other protective member during the
molding process.
[0048] The first plate 66 of the molding apparatus 64 includes a
mold cavity 68 in fluid communication with a pressurized source 70
of a molding compound such as a Novolac based epoxy. The mold
cavity 68 is adapted to receive the molding compound and to mold
the molded plastic body 18 over the encapsulant 16, and on the
circuit side 24 and peripheral edge 28 of the substrate 12. In
addition, the mold cavity 68 is adapted to define features of the
molded plastic body 18 such as the face portion 48 (FIG. 1A) and
the groove 50 (FIG. 1A).
[0049] The first plate 66 and the second plate 72 are configured to
apply pressure to the substrate 12 during the molding process to
prevent molding compound from forming on portions of the substrate
12 such as on the back side 26 thereof (i.e., to prevent "flash"
from forming). The first plate 66 also includes four pins 74
located within the mold cavity 68, which are configured to form the
notches 38 (FIG. 1B) in the molded plastic body 18.
[0050] As shown in FIG. 3C, the pins 74 align with the connecting
segments 54 which attach the substrate 12 to the strip 30. The pins
74 are configured to contact the connecting segments 54 during the
molding process. This forms the notches 38 (FIG. 1B) in the molded
plastic body 18 in exact alignment with the connecting segments 54.
The pins 74 are also configured to apply pressure to the connecting
segments 54, such that molding compound does not flow beneath the
connecting segments 54 and form "flash" on the back side 26 of the
substrate 12. In the illustrative embodiment the pins 74 are
generally cylindrically shaped and form the notches 38 with a
hemispherical shape. However, the pins 74 can have other
geometrical configurations adapted to form the notches 38 in other
shapes (e.g., square, rectangular, quarter moon, etc.).
[0051] Referring to FIGS. 2D and 3D, the molded plastic body 18 is
shown following the molding process. As shown in FIG. 3D, the
notches 38 in the molded plastic body 18 are aligned with the
connecting segments 54. However, the connecting segments 54 remain
intact such that the substrate 18 remains connected to the strip
30.
[0052] Next, as shown in FIGS. 2E and 3E, a singulating step is
performed to sever the connecting segments 54 and separate the
substrate 18 from the strip 30. For performing the singulating
step, a punch apparatus 76 can be provided. The punch apparatus 76
can comprise a conventional punch or press that includes cutters 78
configured to sever the connecting segments 54 at their point of
attachment to the substrate 18. The cutters 78 are sized and shaped
similarly to the pins 74, such that they are able to move through
the notches 38 to sever the connecting segments 54. The notches 38
thus provide access for the cutters 78 to the connecting segments
54.
[0053] Referring to FIGS. 2F and 3F, the card 10 is illustrated
following the singulating step but prior to removal from the strip
30. As shown in FIG. 3F, a peripheral outline 80 of the card 10 is
defined by the peripheral opening 58 through the strip 30. In
addition, the connecting segments 54 in the opening 58 have been
severed such that the card 10 can be removed from the strip 30.
[0054] Referring to FIG. 4, one of the notches 38 is shown in an
enlarged view. In this case, the connecting segment 54 was not
cleanly severed such that a sliver 82 of substrate material
remains. However, the sliver 82 is contained within the notches 38
such that the peripheral outline and dimensions of the card 10 will
meet specification. The notches 38 also function to shield rough
edges that may have resulted from shearing of the connecting
segments 54.
[0055] Referring to FIG. 5, a system 84 configured to perform the
method of the invention is illustrated. The system 84 includes the
strip 30 containing the substrates 12. In addition, the substrates
12 are defined by the peripheral openings 58 in the strip 30, and
are attached to the strip 30 by the connecting segments 54 (FIG.
3A). The system 84 also includes the molding apparatus 64 having
the pins 74 configured to contact the connecting segments 54 (FIG.
3C) during molding of the molded plastic body 18. In addition, the
pins 74 form the notches 38 (FIG. 1A) in the molded plastic body
18. The system 84 also includes the punch apparatus 76 having
cutters 78 configured to sever the connecting segments 54 (FIG.
3E).
[0056] Thus the invention provides an improved semiconductor card,
a method for fabricating the card, and a system for performing the
method. While the invention has been described with reference to
certain preferred embodiments, as will be apparent to those skilled
in the art, certain changes and modifications can be made without
departing from the scope of the invention as defined by the
following claims.
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