U.S. patent application number 10/925574 was filed with the patent office on 2006-03-02 for securing lids to semiconductor packages.
Invention is credited to Bruno Clark, Nitin A. Deshpande, Kyle W. Kippes.
Application Number | 20060042054 10/925574 |
Document ID | / |
Family ID | 35940937 |
Filed Date | 2006-03-02 |
United States Patent
Application |
20060042054 |
Kind Code |
A1 |
Kippes; Kyle W. ; et
al. |
March 2, 2006 |
Securing lids to semiconductor packages
Abstract
A bridge clip can provide off center loading between a lid and a
semiconductor package during curing of adhesive for attachment of
the lid to the integrated circuit die. This may be done, in some
embodiments, without requiring an inventory of different parts and
a variety of different assembly techniques by providing a leaf
spring on the bridge clip which may be adapted for off center
loading. The leaf spring may have its apex or centroid displaced
with respect to the length of the bridge clip, transversely thereto
or some combination thereof as needed. Thus, in some embodiments, a
different leaf spring is all that needs to be provided to implement
off center loading.
Inventors: |
Kippes; Kyle W.; (Chandler,
AZ) ; Deshpande; Nitin A.; (Chandler, AZ) ;
Clark; Bruno; (Chandler, AZ) |
Correspondence
Address: |
TROP PRUNER & HU, PC
8554 KATY FREEWAY
SUITE 100
HOUSTON
TX
77024
US
|
Family ID: |
35940937 |
Appl. No.: |
10/925574 |
Filed: |
August 25, 2004 |
Current U.S.
Class: |
24/458 ;
257/E23.086; 257/E23.09 |
Current CPC
Class: |
H01L 2924/0002 20130101;
H01L 23/4093 20130101; H01L 23/433 20130101; Y10T 24/44026
20150115; H01L 2924/00 20130101; H01L 2924/0002 20130101 |
Class at
Publication: |
024/458 |
International
Class: |
A44B 21/00 20060101
A44B021/00 |
Claims
1. A method comprising: forming a bridge clip with a leaf spring
offset with respect to the centroid of the bridge clip.
2. The method of claim 1 including offsetting said leaf spring
along the length of said bridge clip.
3. The method of claim 1 including offsetting said leaf spring
transversely to the length of said bridge clip.
4. The method of claim 1 including providing a leaf spring for a
bridge clip that has a curved portion and a straight portion, the
straight portion being longer on one side of said bridge clip than
on the other side.
5. The method of claim 1 including providing a leaf spring having a
curved portion and a pair of straight portions on opposed sides of
said curved portion, said curved portion having an apex, said apex
having an offset portion offset away from the centroid of said leaf
spring.
6. A method comprising: using a bridge clip to provide off center
loading between a die and a lid.
7. The method of claim 1 including providing a leaf spring having a
curved portion to apply force to said lid, the apex of said curved
portion being offset with respect to the centroid of said bridge
clip.
8. The method of claim 7 including offsetting said leaf spring
along the length of said bridge clip.
9. The method of claim 7 including offsetting said leaf spring
transversely to the length of said bridge clip.
10. The method of claim 7 including providing a leaf spring for a
bridge clip that has a curved portion and a straight portion, the
straight portion being longer on one side of said bridge clip that
on the other side.
11. The method of claim 7 including providing a leaf spring having
a curved portion and a straight portion and a pair of straight
portions on opposed sides of said curved portion, said curved
portion having an apex, said apex being offset away from the
centroid of said leaf spring.
12. A bridge clip comprising: a bridge; a stiffener coupled to said
bridge; and a leaf spring mounted on said stiffener in an offset
position.
13. The bridge clip of claim 12 wherein said leaf spring includes a
curved portion and two opposed straight portions on either side of
said curved portion, one of said straight portions being longer
than the other of said straight portions.
14. The bridge clip of claim 12 wherein said leaf spring includes a
curved portion and a pair of straight portions on opposite sides of
said curved portion, said straight portions to engage said
stiffener, said curved portion having an apex and a length, the
apex of said curved portion being offset in a direction transverse
to the length of said leaf spring.
15. The bridge clip of claim 12 including a pair of louvers in said
stiffener, said louvers engaged by said leaf spring, said louvers
being symmetrically positioned on said stiffener.
16. A leaf spring for a bridge clip comprising: a curved portion;
and two opposed straight portions on either side of said curved
portion, one of said straight portions being longer than the other
of said straight portions.
17. The leaf spring of claim 16 wherein said straight portions to
fit into louvers in a bridge clip.
18. A leaf spring for a bridge clip comprising: a curved portion;
and a pair of straight portions on opposite sides of said curved
portion, said straight portions to engage a stiffener, said curved
portions including an apex and a length, the apex of said curved
portions being offset in a direction transverse to the length of
said leaf spring.
19. The leaf spring of claim 18 wherein the apex is indented on one
side and includes an outwardly extending prong on the opposite
side.
Description
BACKGROUND
[0001] This invention relates generally to the assembly of
integrated circuit packages.
[0002] In the assembly of integrated circuit packages, an
integrated circuit chip or die may be secured to a lid. This
attachment may involve providing an epoxy adhesive and thermal
grease between the integrated circuit package and the lid. The lid
allows thermal communication between the integrated circuit package
and an integral heat spreader, which takes heat away from the
integrated circuit.
[0003] It is known that the amount of force that is applied between
the lid and the package during the curing of the adhesive is
critical to the ability of the lid to transfer heat from the
package to the integral heat spreader and, ultimately, to heat
dissipation devices such as heat sinks. To this end, bridge clips
may be utilized to apply a force to the lid against the integrated
circuit die during adhesive curing. Generally the bridge clip
includes a U-shaped or T-shaped member, a U-shaped stiffener, and a
leaf spring. The bridge clip clips onto a metal processing carrier
such that the leaf spring is compressed between the stiffener and
the lid, providing a downward compressive force to the lid, pushing
the lid against the integrated circuit die.
[0004] Conventionally, the stiffener includes louvers which secure
the leaf spring in a central location on the bridge clip. Thus,
conventionally, an even and distributed load is applied during the
lid attachment process because the bridge clip clips into slots in
the metal processing carrier, the louvers in the stiffener are
centrally located with respect to the stiffener and the bridge and
the leaf spring is symmetrical.
[0005] However, in some cases, off center dice may be loaded on the
metal processing carrier. These dice may be positioned with respect
to the slots in the metal processing carrier in a way in which
conventional bridge clips provide an uneven force. This problem may
be handled by providing differently sized bridge clips. As a
result, the inventory of bridge clips, metal carriers, and handling
media for handling metal carriers and bridge clips is greatly
increased. This increases the cost of the assembly process.
[0006] Thus, there is a need for a system which handles dice whose
centers may be shifted on metal processing carriers without
requiring excessive inventories of handling media, metal carriers,
and bridge clips.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is an enlarged, exploded perspective view of one
embodiment of the present invention;
[0008] FIG. 2 is an enlarged, top plan view of the leaf spring
shown in FIG. 1 in accordance with one embodiment of the present
invention;
[0009] FIG. 3 is an enlarged, perspective view of the embodiment
shown in FIG. 1 in an assembled condition in accordance with one
embodiment of the present invention;
[0010] FIG. 4 is an enlarged, exploded perspective view of another
embodiment of the present invention;
[0011] FIG. 5 is a top plan view of the leaf spring of the
embodiment shown in FIG. 4 in accordance with one embodiment of the
present invention;
[0012] FIG. 6 is an enlarged, partial view of a metal processing
carrier with bridge clips assembled thereon in accordance with one
embodiment of the present invention; and
[0013] FIG. 7 is an enlarged, cross-sectional view taken generally
along the line 7-7 in FIG. 6.
DETAILED DESCRIPTION
[0014] Referring to FIG. 1, a bridge clip 10 includes a bridge 12
having a pair of spaced handling openings 20. The bridge 12 also
includes a pair of end pieces 14 coupled transversely to the member
18 to form the overall U-shape of the bridge 12 in accordance with
one embodiment of the present invention. The end pieces 14 include
slots 16 engageable by a prong (not shown in FIG. 1) of a metal
processing carrier (also not shown in FIG. 1).
[0015] A U-shaped stiffener 22 may be provided over the bridge 12
in accordance with one embodiment of the present invention. The
stiffener 22 may include openings 26 which align with the openings
20 in the bridge 12. In addition, the stiffener 22 may have
inwardly facing, opposed louvers 30 which retain the leaf spring 32
on the stiffener 22 within the bridge clip 10. In one embodiment of
the present invention, the louvers 30 may be symmetrically
positioned on the stiffener 22 which is symmetrically positioned on
the bridge 12.
[0016] Asymmetry may be provided in the length direction of the
bridge clip 12 by the use of an offset leaf spring 32. The leaf
spring 32 has a curved section 36 and a pair of opposed flanges 34.
The flanges 34 enable the leaf spring 32 to be retained by the
louvers 30 on the stiffener 22. Off center loading is achieved
because of the extension 35 of one flange 34 as shown in FIG. 2.
The extension 35 serves as a flat portion of the leaf spring,
reducing the extent of the curved portion 36 and moving its center
along the length of the bridge clip 12. As a result, the bridge
clip 12 may be used for off center loading of lids to dice in metal
processing carriers which are otherwise unchanged. In other words,
by simply changing the leaf spring 32, off center loading may be
implemented without otherwise changing the bridge clip 10 or the
metal processing carrier.
[0017] As shown in FIG. 3, the leaf spring 32 is centrally loaded
into the symmetrically arranged louvers 30 of the stiffener 22,
which is then held on the bridge 12. The end pieces 14 may have
prongs 37 which control the position and extent of engagement
between the bridge clip 10 and the metal processing carrier (not
shown in FIG. 3). The various apertures 26 and 20 may be used by
automated equipment to place the bridge clip 10 on the metal
processing carrier over a lid and integrated circuit die.
[0018] While the embodiment shown in FIGS. 1-3 allows off center
loading shifted in a direction along the length direction of the
bridge clip 10 with respect to its centroid, it may also be
desirable to provide off center loading in a direction transverse
to the length of the bridge clip. The embodiment shown in FIGS. 4-7
permits such off center loading.
[0019] The structure shown in FIG. 4 is identical to that shown in
FIG. 1 except that the leaf spring 32 is replaced with a leaf
spring 32a. The leaf spring 32a does not include the offset portion
35. Instead, it includes an indented section 40 at the peak of the
curved portion 36a and an opposing protruding portion 38 at that
same peak. As a result, the peak at which the force is applied by
the leaf spring 32a has its centroid shifted towards the viewer in
FIG. 4, providing offset loading in a direction transverse to the
length of the bridge clip 10a.
[0020] This is better shown in FIG. 5 where it can be seen that the
flanges 34 are symmetrical. No portion 35 is included, but the
portion 38 extends upwardly in FIG. 5 and the section 40 is
upwardly indented, shifting the center of applied force of the
spring 32a upwardly in the embodiment shown in FIG. 5.
[0021] Referring to FIG. 6, a metal processing carrier 50 may be
utilized to secure lids 52 onto integrated circuit dice 56. In this
case, each bridge clip 10 includes a bridge 12 which clips into
appropriately sized apertures 53 in the metal processing carrier
50. Thus, the prongs 37 may rest on the upper surface of the
carrier 50.
[0022] In one embodiment, the apertures 53 provided in the carrier
50 may produce an angled orientation of the bridge clip 12, as
indicated in FIG. 7. Depending on the size and location of the lid
56, it may be desirable to provide an off center loading. In this
case, the off center loading may enable the point of maximum force,
applied by the leaf spring 32 against the lid 52, to be off center
along the length of the bridge 12 or transverse thereto, as needed,
or even, in some cases, off center in both the length and
transverse directions.
[0023] The apertures 53 in the carrier 50 receive the end pieces 14
on the bridge 12 and lock the bridge clip 10 thereon. The tongues
51, defined in the carrier 50, adjacent the apertures 53,
releasably lock the bridge clip 10 in place. In particular, the end
pieces 14 cam inwardly as they engage the apertures 53 until they
are pushed sufficiently far to spring back and be locked by the
tongues 51 which engage the apertures 16 in the bridge 12 end
pieces 14. In this position, the leaf spring 32 is offset to the
right because of the provision of the extension 35. Off center
loading of the lid 52 against the package 56 is possible. Thus, an
off center of force may be applied to adhesively secure the lid 52
to the package 56.
[0024] In some embodiments, off center force may be applied to dice
without requiring the provision of different handling media,
different bridges, and different stiffeners for each variation.
This reduces the inventory of components and the inventory of
different assembly techniques, reducing the cost of assembly in
some cases. Leaf springs may be modified to accommodate a variety
of offset die scenarios. This may be accomplished without requiring
different carriers, different stiffeners, or different bridges in
some embodiments. Thus, a variety of different sizes and
orientations of lids and dice may be accommodated without excessive
costs. Similarly, the assembly equipment need not be modified in
any way in some embodiments of the present invention.
[0025] While the present invention has been described with respect
to a limited number of embodiments, those skilled in the art will
appreciate numerous modifications and variations therefrom. It is
intended that the appended claims cover all such modifications and
variations as fall within the true spirit and scope of this present
invention.
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