JPH02501178A - Method and apparatus for packaging and cooling integrated circuit chips - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Methods and equipment technology for packaging and cooling integrated circuit chips The present invention generally relates to tape automated bonding (TAB) integrated circuit chips. METHODS AND APPARATUS FOR PACKAGING AND COOLING.

Background technology Removing heat from integrated circuit (IC) chips requires careful engineering. This is a central issue in modern high-performance electronic packaging. Awareness of heat management The standard method is based on other package engineering or performance requirements. It is often not suitable. Incorporating heat dissipation structures within circuit chip modules This often disadvantageously increases the complexity and size of the mechanical structure. substitute Designs that do not incorporate temperature-related structural and electrical failures.

A number of different schemes have been proposed to avoid these problems. Usually these Some methods include heat sinking the chip module housing or package. This includes using it as a security guard.

To ensure maximum cooling of the chip housed within the housing, the chip the heat sink in such a way that there is good thermal conductivity between them. Mechanically coupled. However, this reduces the stiffness between the housing and the circuit chip. mechanical bonding is a problem because it can create excessive stress on the chip that can cause damage. There is a problem. On the other hand, if a less rigid mechanical bond is used, the heat sink can be removed from the chip. This reduces the efficiency of heat transfer to the It increases accordingly.

created by the need to connect each circuit chip directly to a common heat sink or housing. Another problem is that due to the dimensional tolerances of each chip on the mounting board, the module Difficult to ensure that any chip in the module is evenly connected to the housing That's true.

Some chips have no direct connection to the housing at all, while others have excessive mechanical Even physical stress may be applied.

Many solutions have been proposed to date for the above problems. such one One solution was developed by IBM to package ICs in thermally conductive modules manufactured by IBM. It is used for cooling and contacting the back side of the chip to maintain mechanical morphology and A dedicated piston is used within the heat sink to allow for variations in temperature and tolerance. but, This method is mechanically complex and therefore costly. Other methods use chips and To fill the gap between heat sinks, use solder or ) using thermally conductive materials such as thermal compounds to ensure mechanical and thermal contact and to ensure dimensional tolerances. The flexibility (compliance), that is, the elastic action necessary to tolerate changes in the difference, is Little or no presence.

Disclosure of invention The present invention seeks to overcome the drawbacks of the prior art.

It is therefore an object of the present invention to provide heat shielding without creating excessive mechanical stress. The chip can be integrated into one piece without having to configure the link and chip assembly to tight dimensional tolerances. The IC chip is packaged in such a way that it is kept in direct thermal contact with a heat sink. An object of the present invention is to provide an improved method and apparatus for storage and cooling.

Another object of the invention is that the heat sink provides a protective hermetic confinement (enclosure) for the chip. Provides an efficient cooling structure for electrical circuit chips There is a particular thing.

Yet another object of the invention is to improve thermal management through improved thermal management and reduced mechanical and thermal stresses. Provides a method and apparatus for cooling an electrical circuit chip that can improve the reliability of the chip. It's about doing.

A further object of the invention is to eliminate the need for bonding the housing of the chip to the substrate, thus For circuit chips, such as allowing easy removal of the chip for replacement or rework. The objective is to provide a cooling and packaging structure.

The above and other objects of the present invention are to provide a plurality of TAB type chips with circuit sides facing downward. a base for supporting the pipe; and a protective containment body attached to the base; a plurality of cooling fins that enable the enclosure to act as a heat sink; By providing a circuit chip module or assembly with a top side thereof achieved. When the heatsink is in place, the inside top surface of the heatsink is It is designed to come into contact with the back side of the IC chip. Alternatively, separate the chips The chip may be mounted in an intermediate housing or the chip may be in contact with a heat sink. An intermediate heat spreading structure may also be included.

The heat sink also receives a resilient gasket or O-ring on its underside. It has a peripheral recess for When the heatsink is positioned on the base, the gas The sket acts as a sealing ring and is assembled with the heat sink and base. For IC chips that prevent IC chips from being exposed to external moisture, chips, etc. form a protective confinement.

Made of multiple resilient elastomers to accommodate variations in assembly dimensional tolerances A pad or cushion is disposed between each IC chip and the base. child These pads generally have a shape corresponding to each IC chip, such as a circular or rectangular shape. It can be the shape of a shape. The IC chip is placed on these pads, but No joining is done. Instead, connect the pins on the base board from each side of the TAB chip. A flexible circuit lead frame that extends to the ground pad is bonded to the base. Fix the chip to the base.

With the heatsink attached to the base, the inner top surface of the heatsink should touch Make contact with the back side of the chip or the housing for the chip, without touching the cushion on the bottom of the chip. Compress the crab. A TAB-shaped flexible lead frame allows this vertical movement. Noh. This ensures that each chip stays firmly in place without excessive stress. The balance is maintained. In addition, the compression of the cushion increases the amount of stress between the chip and the heat sink. The increasing pressure creates intimate mechanical contact between each chip and the heat sink, causing Increase heat transfer.

To further improve heat transfer between the chip and heatsink, the interface between the two Very thin films of non-diffusive, low vapor pressure fluids such as liphenyl ethers or liquid metals caused by the uneven contact between the chip and the heat sink's mating surface. Fills the microvoids that exist. Alternatively, gap for this purpose may be filled with gas, but it is sensitive to misalignment and small changes in interfacial pressure. It is preferable to use liquid from the point of view.

Low stress separable interface between each chip and heat sink reduces thermal stress on the chip Possible failure of the passivation moisture barrier through cracking or micro-cracking. This improves the reliability of the overall structure by reducing the Also, chips and Slip-free heat sink interfaces reduce thermal dissipation between various parts of the assembly. Matching reduces the tendency of TAB frames to induce thermal cycle fatigue . This, combined with the excellent heat conduction properties at the interface and the tightness of the confinement, relatively simple in construction and reliable against thermal and mechanical side stresses and external conditions. To provide an assembly for an IC chip that provides excellent protection to the chip.

It will become clear by considering the following detailed description of the preferred embodiment with reference to Become. In addition, 2 in the figure Figure 1 is an exploded perspective view of an assembly housing multiple IC chips; Figure 2 is a TAB type chip. the chip, the mounting board, and the elastic cushion placed between the chip and the board. Disassembled perspective view 2. Figure 3 is a partial sectional view of the assembly: and Figures i4A and 4B are partial cross-sections of the assembly showing the structure of different types of chip housings. It is a diagram.

Best mode for carrying out the invention Next, considering the present invention in more detail, a plurality of TAB type IC chips 12 are housed. An assembly 10 for the purpose is shown. Each chip 12 is typically a silicon wafer. It consists of an integrated circuit embedded in or disposed on. The assembly 10 is made of gold. The base support plate 14 is preferably constructed of metal or rigid plastic. include. Embedded circuitry on plate 14 that provides power and signals to IC chip 12 A conventional ceramic format substrate 16 containing (not shown) is disposed. Ru. A multilayer thin film substrate 18 is disposed on top of the format substrate 16, and Based on a plurality of bonding pads (not shown) disposed on the top of thin film substrate 18. It includes a plurality of embedded conductors that provide power and signals from plate 16.

As usual, each TAB type IC chip 12 is attached to a flexible circuit lead frame. a lead frame 20 formed on a thin carrier film; It extends from all sides of the chip.

The lead frame 20 is bonded to a bonding pad on the thin film substrate 18, and each The chip 12 is electrically connected to the thin film substrate 18 and mechanically fixed.

It is attached to the bottom edge of the mat substrate 16 by soldering.

These connectors 22 connect the format board 16, thin film board 18 and lead frame. Power and signals are supplied to the circuit chip 12 through the system 20 .

The heat sink and protective cover 28 has a plurality of holes (not shown) in the heat sink 28. and inserted into the plurality of holes 32 of the board 16, the base support plate 14, and the connector 22. It is fixed to the format board 16 and the base support plate 14 with a plurality of screws 30. be done. The heat sink 28 includes a plurality of heat conductive fins 33 provided on the top thereof. The chip 12 is preferably made of a metal with good thermal conductivity. It also acts as an electromagnetic shielding means. O-ring or resilient gasket 34 is disposed between the heat sink 28 and the format board 160, and the circuit chip 1 2 is sealed against external dust, water, corrosive gas, etc.

Referring now to FIG. 2, one TAB type circuit 40 containing the IC chip 12 is shown. The IC chip 12 has its circuit side facing down, and the back side 41 has film type leads. It is disposed facing upward on the frame 20. The lead frame 20 has an IC at one end. A plurality of circuit leads 42 are provided connected to the chip 12. Other than circuit lead 42 The end is located on the thin film substrate 18 when the circuit 40 is in place on the multilayer thin film substrate 18. It is located so as to be joined to a plurality of bonding pads 43 of.

A resilient cushion or pad 44 is disposed between the thin film substrate 18 and the chip 12. be done. This cushion 44 is shown in a circular shape in FIG. It can be any shape that approximately corresponds in size and shape to that of No. 2. So that the water is less A heat sink 28 is attached to the assembly and is in contact with the back side of the circuit chip 12. The cushion 44 is designed to be placed under compression when the cushion 44 is placed under compression. Therefore , the cushion 44 is made of silicone rubber such as Viton. It has a low elastic modulus to avoid high stress and is easy to assemble and clean. and should be made of materials compatible with each step of the test. cushion 44 The thickness should be no more than about 25% compressible. In one experiment, 0 ．． Successful results were obtained using a cushion with a thickness of 0.01 inch.

A partial cross-section of the assembled assembly 10 is shown in FIG.

As shown, the heat sink 28 is configured to engage the back side of the downward facing chip 12. It has an internal top surface 46 located at . However, when the heat sink 28 is placed on the base support plate, A non-diffusion, low vapor pressure dielectric flow prior to fixation to the substrate 14 and format substrate 16 A thin film of body 50 is applied to the back side of chip 12. This fluid film acts as a heat sink. By filling the microvoids caused by the uneven contact between the two engaging surfaces of the chip, Increases heat transfer between the two. 5- and 6-cyclic polyphenyl ethers (PPE ) as a fluid 50 and it was found to work very well. Ta. Alternatively, a thin layer of fluid 50 may be placed with liquid metal or gas contained within the assembly. You can also change it.

The internal top surface 46 of the heat sink 28 has a smooth surface using standard machining techniques. , further ensuring that low thermal contact resistance is achieved between the chip and the heat sink. There is. Typically, the backside surface of each chip 12 has adequate smoothness by itself. . Generally, the spacing between the non-textured contact surfaces of the chip and the heat sink is 0.5 to 2.0 mm. This corresponds to the required thickness of the fluid film 50 between Krons.

The heat sink 28 is formatted with the base support plate 14 as shown in FIG. When assembled to the board 16, the internal top surface 46 faces downward with the back side of the tip 12. abutting and slightly compressing the cushion 44. This movement is performed by This is possible due to the inherent vertical flexibility of the frame 20. In this way, A low stress but efficient thermal interface is achieved between heat sink 28 and circuit chip 12 be done. The compressibility of the cushion 44 is limited by any slight compressibility that may exist within the assembly. to compensate for dimensional variations and maintain close contact between each chip 12 and the heat sink 28. Ensures that mechanical and thermal contact is maintained. In Figure 3, heat sink 28 A resilient gasket 34, shown disposed in a peripheral recess 52 in the bottom of the base support plate, With the heat sink 28 assembled on the chip 14, the hermetic closure for the chip 12 is opened. It plays a role in forming the inlay 54. As mentioned above, the gasket 34 2 to protect it from external moisture, dust, gas, etc.

Referring now to FIGS. 4A and 4B, two alternative embodiments of the present invention are shown: A circuit chip 12 is bonded to or within an intermediate housing or structure. include. That is, in FIG. 4A, the circuit chip 12 is an outer shell (Taram shell). It is shown included in a housing 60, which includes a high thermal conductivity cell. It is preferably formed of ramic and includes a lower half 62 and an upper half 64. this Seal means 66 and 68 are disposed between the engaging surfaces of the two halves, and these seals A TAB lead frame 20 of the chip 12 extends through the means. In other words, outside A shell housing 60 provides a hermetic confinement for the chip 12.

An elastic cushion 44 is disposed under the lower half 62 of the outer shell housing 60, and The cushion 44 is placed on the multilayer thin film substrate 18 and the format substrate 16. . The upper portion 64 of the outer housing 60 is in close contact with the inner top surface 46 of the heat sink 28. are kept in contact and a fluid layer 50 is provided between these two elements as in FIG. This increases heat transfer between the two. This means that the chip 12 is joined to the inner surface of the upper part 64. Combined with the fact that Give passage.

The embodiment shown in FIG. 4B is similar, but the outer shell housing 60 is replaced by a heat spreading element. 70 is used. A heat spreading element 70 is bonded to the chip 12, with the top surface of the element It is maintained in contact with the inner top surface of the heat sink 28. Same as the previous example , a fluid layer 50 is provided between the heat sink 28 and the heat spreading element 70 .

Two types of resilient cushions 44a and 44b are provided: the latter under the chip. The former is arranged below the depending legs 72 and 74 of the heat spreading element 70. Ru.

The embodiment shown in FIGS. 4A and 4B performs the same function as the embodiment shown in FIG. , further provides additional sealing and heat dissipation means for the chip 12.

Having thus illustrated the invention in connection with preferred embodiments, it is set forth in the following claims. Numerous variations and modifications will occur to those skilled in the art without departing from the true spirit and scope of the inventive concept. Of course it is possible.

F5 yo) R 107 terri 1st investigation report

Claims (20)

[Claims] 1. In an assembly for packaging and cooling circuit chips: at least the first a base for receiving a circuit chip; disposed between the base and the first surface side of the circuit chip; resilient means placed; and A heat sink engaged with the base and in contact with the second side of the circuit chip. a state in which the resilient means is compressed and engaged with the heat sink or the base; and a heat sink including means for increasing the contact pressure between the heat sink and the second side of the circuit chip. assembly with a seat sink; 2. The means that contacts the second surface side of the circuit chip is the inner top surface of the heat sink. An assembly according to claim 1, comprising: 3. a circuit disposed between the heat sink and the base and received within the assembly; Claim 1 further comprising sealing means for protecting the chip from external ambient conditions. The assembly according to item 1. 4. In an assembly for packaging and cooling circuit chips: a base; a resilient means disposed on the base; a first surface side placed on the resilient means; , at least a first circuit chip with a second side facing upward; and the pace and A heat sink to be engaged, in contact with the second side of the circuit chip, and in contact with the contact means and the front side. The elasticity is increased so as to increase the contact pressure between the second surface sides of the circuit chip and thus the thermal conductivity. a heat sink including contact means for compressing the sexual means; 5. A thin film of fluid is provided between the second surface side of the circuit chip and the contact means, and 5. The assembly according to claim 4, further increasing the thermal conductivity between the parts. 6. 6. An assembly according to claim 5, wherein said fluid is a liquid. 7. 7. An assembly according to claim 6, wherein said liquid is a polyphenyl ether. 8. 7. An assembly according to claim 6, wherein said liquid is a liquid metal. 9. 6. An assembly according to claim 5, wherein said fluid is a gas. 10. disposed between the heat sink and the base, and connecting the circuit chip to an external periphery. further comprising sealing means to form a hermetic confinement for the chip to protect it from ambient conditions. The assembly according to claim 4. 11. Claim 4, wherein said contact means comprises an internal top surface of said heat sink. The assembly shown. 12. A flexible circuit lead frame mechanically and electrically supports the circuit chip on the first side. a plurality of bondings mounted on the base on the second surface side; 5. An assembly according to claim 4 attached to a pad. 13. The elastic means has a size approximately corresponding to the circuit chip, and the elastic means has a size substantially corresponding to the circuit chip. at a predetermined location between the circuit chip and the base by means of a circuit lead frame. It consists of a thin elastomeric cushion that is held in place and that is exposed to the heat. Claim 1, wherein pressure is applied through the tip by contact means of a sink. The assembly described in item 2. 14. The circuit chip and the circuit lead frame are bonded using tape automatic bonding (T 13. An assembly according to claim 12 forming an integrated circuit of type AB). 15. bonded to the second surface side of the circuit chip and engaged with the contact means of the heat sink; 5. The assembly of claim 4 further comprising a mating intermediate structure. 16. The heat sink is made of gold that acts as an electromagnetic shield for the circuit chip. 5. The assembly of claim 4, wherein the assembly is formed of genus. 17. In the method of packaging and cooling circuit chips: base elastic means placing at least a first circuit chip on said resilient means; placing at least a first circuit chip on said resilient means; loosely arranging the surface side facing down and the second side facing upward; and a heat sink having contact means that closely engages the second side of the circuit chip; the circuit chip by engaging the pace and compressing the resilient means; While firmly holding it in place, the second side of the circuit chip and the heat providing a mechanical interface of high thermal conductivity between the sinks. 18. The second surface side of the circuit chip before engaging the heat sink with the base. coated with a thin layer of fluid to further enhance heat transfer properties between the chip and the heat sink. 18. The method of claim 17, further comprising a step. 19. A flexible circuit lead frame is attached before the heat sink is engaged with the base. a first end to the circuit chip and a second end to a plurality of bonds disposed on the base. 18. The method according to claim 17, further comprising the step of respectively bonding to the padding pads. Method. 20. Before engaging the heat sink with the base, the heat sink and the base arranging sealing means therebetween to form a hermetic confinement for said circuit chip; 18. The method of claim 17, further comprising: