Pivotal heat sink assembly

This invention provides a heat sink assembly for cooling electrical and electronic circuits. A low cost assembly method is achieved by a pivotal assembly containing a heat sink which snaps into place adjacent to an electrical/electronic circuit which requires cooling. The snap-in heat sink assembly contains a resilient heat transfer material which is exposed to the devices requiring heat removal by windows or other openings in a plate which is disposed between the heat transfer material and the snap-in frame.

DESCRIPTION 
1. Technical Field 
The present invention relates to a heat sink apparatus for cooling 
electrical and electronic components. 
2. Background of the Invention 
Heat dissipation is an elementary requirement for most any electrical 
circuit, and when air alone will not suffice to dissipate the requisite 
amount of heat generated by these electrical devices, heat sinks are used 
to augment heat dissipation. Ways to dissipate heat via heat sink devices 
vary. and some of the more common devices use a series of fins connected 
to a rigid plate, the plate being placed in contact with the device to be 
cooled. The fins provide increased surface area for the surrounding air, 
and increase the rate of heat dissipation which would occur if the surface 
area of the heated device itself were used. The use of liquids to cool 
electrical devices is also known and operate on a principle similar to the 
way a radiator in an automobile is used to keep the engine relatively 
cool. 
The types of heat sink devices in use today tend to be somewhat cumbersome 
to assemble and manufacture, however. Most systems employ heat sinks which 
are manufactured in such a way that the heat sink becomes integral with 
the electrical device being cooled, and are thus difficult to handle 
efficiently in a high-volume manufacturing environment. 
Use of heat sinks with semiconductor devices mounted on a flexible 
substrate are known in the prior art. U.S. Pat. No. 4,914,551 discloses 
such a method, and shows how the heat sink becomes integral to the 
electrical device. In that patent, the heat sink is soldered to the 
electrical device carrier. 
Other methods of improving the attachment of heat sinks to power devices, 
and not to semiconductor devices mounted on flexible materials, use clips 
as shown in U.S. Pat. No. D307540. In that patent, the power device is 
again physically attached to the heat sink, with a clip attaching a second 
surface area of the power device to a fin of the same heat sink. 
The prior art has not addressed a heat sink device that can be readily 
attached to a preexisting electrical assembly having semiconductor devices 
attached to a flexible substrate. 
It is therefore an object of the present invention to provide an improved 
heat sink device. 
It is a further object of the present invention to provide an improved heat 
sink device for use with electrical devices attached to a flexible 
substrate. 
It is yet another object of the present invention to provide an improved 
heat sink device designed for ease of manufacturing. 
It is still another object of the present invention to provide an improved 
heat sink device which is easy to attach to an electronic carrier. 
These and other advantages will be more fully described in the following 
description of the invention. 
SUMMARY OF THE INVENTION 
This invention provides a heat sink assembly for cooling electrical and 
electronic circuits. A low cost assembly method is achieved by a pivotal 
assembly containing a heat sink which snaps into place adjacent to an 
electrical/electronic circuit which requires cooling. The snap-in heat 
sink assembly contains a resilient heat transfer material which is exposed 
to the devices requiring heat removal by windows or other openings in a 
plate which is disposed between the heat transfer material and the snap-in 
frame. For attachment to the electrical device carrier the carrier has a 
base plate having a slot, and the snap-in heat sink assembly is inserted 
in the slot and pivoted into position, where a catch on the snap-in frame 
latches to the electrical device carrier.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 shows carrier/stiffener 18 which has a substrate 25 attached thereto 
and in the preferred embodiment this substrate is composed of a flexible 
Copper Invar Copper material. Invar being an alloy of nickel-iron. This 
substrate 25 has direct C-4 chips or other electrical components 24 
attached thereto. forming a carrier assembly 16. 
FIG. 2 shows a vertical heat sink assembly 10 positioned prior to 
installation into the base 12. This vertical heat sink assembly 10 has a 
frame 30, the frame 30 having a lip 38 extending along the bottom edge of 
the frame. Frame 30 further has a catch 40 extending along the top edge of 
the frame. A base 12 has a slot 32 for accepting lip 38 of the heat sink 
assembly. 
FIG. 3 shows the vertical heat sink assembly 10 after installation in the 
base 12. To cool the chips 24, the heat sink assembly 10 is attached 
adjacent to the carrier assembly 16 as follows. Assembly 10 is inserted in 
slot 32 of base 12 (as shown in FIG. 2) and is rotated until all chips are 
in contact with a compliant heat conducting element 26. A catch 40 is then 
latched onto carrier 18 via clip 28. This heat sink assembly 10 has 
individual fluid bags or compressible heat conducting media attached at 
each chip location for cooling. 
FIG. 3 further shows the carrier assembly 16 attached to circuit board 14 
via buckling beam strips, as disclosed in U.S. Pat. No. 4,943,242, 
assigned to the same assignee as this patent application, and hereby 
incorporated by reference. Base 12 rests on top of circuit board 14, and 
in the preferred embodiment also extends along the edge of the circuit 
board and is attached thereto by screws or adhesives. It should be 
understood that other alternative means to attach the base to the circuit 
board are known in the art, and only the preferred embodiment is here 
shown. Base 12 holds buckling beam strips at the area in contact with the 
edge connector 20 of carrier 18, as further described in the above 
referenced incorporated patent. 
FIG. 4 shows a detailed view of the unassembled heat sink assembly. Frame 
30 surrounds a window 34. In the preferred embodiment, this window is 
substantially rectangular with the exception of retaining corners 36. The 
frame 30 has a lip 38 extending laterally along the bottom edge of the 
frame. The frame further comprises a catch 40 extending laterally along 
the top portion of frame 30. In an alternate embodiment, this catch might 
only reside at the two ends, or be spaced along the top portion of the 
frame 30 in a non-continuous fashion. A retainer plate 42 having retainer 
windows 44 and outer edges 39 is positioned adjacent to the frame 30 and 
covers the window 34 such that the corners of the outer edge 39 are 
positioned substantially adjacent to the retaining corners 36 of the frame 
30. 
FIG. 5 shows a particular embodiment of the retainer plate assembly 13 
having a heat sink face 56 attached to the back side 27 of the retainer 
plate 42. This face 56 has a fluid filled compliant element attached 
thereto, forming a compliant interface to the integrated circuit chips or 
modules which are to be cooled. This face 56 further comprises heat sink 
fins 54 radiating away from the retainer plate 42. 
FIG. 6 shows an alternate embodiment of this retainer plate assembly 13 
which also has a heat sink face 56 attached to the back side of the 
retainer plate 42. However, instead of using heat sink fins to dissipate 
heat, a heat transfer bag 60 is a part of the heat sink face 56. This 
transfer bag 60 has ports 62 for the intake and outtake of fluids used in 
a conventional forced fluid flow cooling process. 
In regards to either FIG. 5 or FIG. 6, the retainer plate assembly will 
have its retainer plate 42 attached to the frame 30 in the manner for 
attachment as described in FIG. 4. In this attachment, the heat sink fins 
54 or heat transfer bag 60 extend through the window 34 of frame 30 in 
FIG. 4 and protrude out the back side of the frame 30. This protruding 
heat sink is similarly shown in FIG. 2. 
While we have illustrated and described the preferred embodiments of our 
invention, it is to be understood that we do not limit ourselves to the 
precise constructions herein disclosed and the right is reserved to all 
changes and modifications coming within the scope of the invention as 
defined in the appended claims.