Chip and heat sink non-welding connection method and structure

Abstract

A non-welding connection method and structure for a chip and a heat sink are characterized in that the method comprises the following steps: firstly, one end of a spring piece is welded and connected with the heat sink, the other end of the spring piece is opposite to the position, where the chip is installed, of the heat sink at set pressure and a set gap, secondly, the other end of the spring piece is lifted, and the chip is placed on the lower portion of the spring piece; the other end of the spring piece is loosened, and the chip is pressed on the surface of the heat sink through the elastic edge, thereby completing the connection between the chip and the heat sink. The method solves the problem of chip damage caused by overlarge difference between the heat sink and a chip thermal expansion system, and has the advantages of simple method and structure, convenience, rapidness and reliability.

Description

Technical Field

[0001] This invention relates to a semiconductor interconnection technology, particularly a chip-heat sink interconnection technology when the difference in thermal expansion coefficients between the chip and the heat sink is 5 or more, specifically a non-welding connection method and structure between the heat sink and the chip. Background Technology

[0002] Currently, high-power-density chips generate a lot of heat per unit area, requiring timely heat dissipation through a layer-by-layer transfer to the outside of the electronic device. Heat sinks (micro-heat sinks) are micro-electronic components directly connected to the chip for heat dissipation. They are typically composed of AlN or CVD diamond substrates with a thickness of 0.1-0.8mm and dimensions slightly larger than the connected chip; their surfaces are coated with various metals and solders required by the customer. Currently, the thermal conductivity of diamond, the substrate material for CVD diamond heat sinks, can reach over 1000W / mK, and it will be a key type of heat sink substrate to be developed in the next few years.

[0003] In existing technologies, the heat sink and the chip being cooled are connected via eutectic bonding. Eutectic bonding requires pre-applying gold-tin solder to the heat sink. During the eutectic bonding process on the production line, the solder is typically aligned with the chip position using a tooling fixture, and a certain pressure is applied in the vertical direction. The temperature is then raised to approximately 300°C in a protective gas atmosphere, held for a few seconds, and then cooled. Generally, the larger the area of ​​the solder, the better the bonding strength. Some specialized industries require a lateral thrust greater than 2 kg / mm² for tests that damage the solder layer. 2 Chinese patent 2013101493228 discloses an elastic connection structure, but its structure is complex and costly, and the main function of its spring is to absorb thermal strain rather than to connect. Chinese patents with publication numbers CN105428994B and CN209747556U, and application numbers 200710144581.6 and 202210708106.1, all disclose corresponding chip heat sink connection methods, but they all require welding technology to achieve the connection between the chip and the heat sink. There is often no good solution for this.

[0004] However, the thermal expansion coefficient of certain large-sized chips (such as high-power-density GaAs laser chips, which are generally longer than 5mm and have a thermal expansion coefficient of around 6ppm / K) differs greatly from that of CVD diamond (around 1ppm / K). The strong bonding force of the solder after cooling can cause the chip, which is much less hard than diamond, to tear. Therefore, it cannot be reliably used at present. Summary of the Invention

[0005] The purpose of this invention is to address the problems of chip damage and excessive cost associated with existing chip-heat sink soldering connections due to differences in their coefficients of thermal expansion. The invention provides a method and structure for achieving a mechanical connection between the chip and the heat sink using a spring. This connection is achieved through a transitionally molded, elastic chip-heat sink connection structure based on a pry bar mounting.

[0006] One of the technical solutions of this invention is: A non-soldering connection method for a chip and a heat sink is characterized by: first, welding one end of a spring sheet to the heat sink, and aligning the other end of the spring sheet with the chip mounting position on the heat sink at a set pressure and gap; second, using a pry bar to lift the other end of the spring sheet and placing the chip under it; removing or rotating the pry bar to loosen the other end of the spring sheet and using the elastic edge to press the chip onto the surface of the heat sink, thus completing the connection between the chip and the heat sink.

[0007] The spring sheet serves as the connecting gold wire for the chip, providing electrical conductivity.

[0008] The spring sheet has a single-claw structure, and each chip is fixed using at least one single-claw spring sheet.

[0009] The single-claw structure has two or more spring plates. The single-claw spring plates are arranged along one side of the chip, two adjacent sides, two opposite sides, or three sides. The side without spring plates is opposite to the direction of force.

[0010] The spring sheet 9 has a double claw structure, consisting of a bottom edge 1, a transition edge 2, and two pressure claws 3 that are welded to the heat sink 7. The bottom edge 1 has a process notch 4. The transition edge 2 is connected to the bottom edge 1 and has a curved pressure claw 3 on each side. The front end of the curved pressure claw 3 has a flat plate segment 5 that abuts against the surface of the chip 6.

[0011] The pressure claw 3 is fitted with a slider 8 for adjusting the elastic pressure to prevent excessive pressure from damaging the chip.

[0012] The second technical solution of the present invention is: A non-welded connection structure between a chip and a heat sink includes a chip 6 and a heat sink 7, characterized in that: the bottom edge 1 of a spring sheet 9 is welded to the heat sink 7, and the clamping claw 3 of the spring sheet 9 is pressed onto the chip 6, thereby realizing a non-welded connection between the chip 6 and the heat sink 7.

[0013] The spring plate 9 has a double claw structure, consisting of a bottom edge 1, a transition edge 2, and two pressure claws 3 that are welded to the heat sink 7. The bottom edge 1 has a concave notch 4. The transition edge 2 is connected to the bottom edge 1 and has a curved pressure claw 3 on each side. The front end of the curved pressure claw 3 has a flat plate segment 5 that abuts against the surface of the chip 6.

[0014] The pressure claw 3 is fitted with a slider 8 for adjusting the elastic pressure to prevent excessive pressure from damaging the chip.

[0015] The difference in the coefficients of thermal expansion between the chip 6 and the heat sink 7 is not less than 2, preferably not less than 5.

[0016] The beneficial effects of this invention are: This invention avoids chip tearing caused by uneven thermal expansion; customers can eliminate the need for expensive eutectic bonding equipment. It also eliminates the need for traditional and costly gold-tin solder, allowing the use of more economical solders such as silver-tin-copper. In some customer solutions, this miniature metal spring can even function as a miniature wire, saving customers the cost of one or two gold wires.

[0017] This invention utilizes a spring clip to clamp the chip, with at least one spring clip, replacing gold-tin eutectic bonding. This expands the application range of heat sink materials with better thermal conductivity in terms of size and space, improves heat dissipation, avoids chip damage, and further enhances chip performance.

[0018] This invention utilizes a pry bar as a transitional tool when welding spring sheets and installing chips, which improves welding speed and accuracy, while also maintaining the required elasticity of the spring sheets and preventing the spring sheets from directly contacting the chip during the welding process and transferring heat to the chip, thus preventing damage to the chip.

[0019] The present invention has a simple structure and is safe and reliable. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the connection structure according to Embodiment 1 of the present invention.

[0021] Figure 2 This is a schematic diagram of the connection structure in Embodiment 2 of the present invention.

[0022] Figure 3 This is a schematic diagram of the spring sheet in Embodiment 2 of the present invention. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments. Example

[0024] like Figure 1 As shown.

[0025] In this embodiment, the heat sink 7 is made of CVD diamond with a coefficient of thermal expansion of 1. The coefficient of thermal expansion of the chip 6 is 5.5 or 10. The chip 6 has a side length of 5 mm or more. For chips with a side length of less than 3 mm, when soldering to the heat sink, the contact area is small, so the stress caused by the thermal expansion and contraction of the chip is less affected, and the method of this invention can be disregarded. Therefore, the connection method and structure of this embodiment are suitable for connections with a difference in coefficients of thermal expansion of 2 or more. In this embodiment, the difference in coefficients of thermal expansion is 5. A non-soldering connection method for a chip to a heat sink involves first soldering one end of a spring sheet to the heat sink, aligning the other end of the spring sheet with the chip mounted on the heat sink at a set pressure and gap; secondly, lifting the other end of the spring sheet to place the chip underneath it, and then releasing the other end of the spring sheet. Figure 1 The spring plate is lifted using the pry bar 10, and the chip is then placed on the heat sink. Once in place, the pry bar 10 is removed. The chip 6 is pressed onto the surface of the heat sink 7 using the elastic edge, completing the connection between the chip 7 and the heat sink 6. In practical use, the spring plate 9 can also serve as a conductive gold wire connecting the chip, thereby reducing the original gold wire structure. The spring plate can be made of... Figure 1 The single-claw structure shown uses at least one single-claw spring plate to secure each chip. Figure 1 The chip 6 is held in place by six single-claw spring plates 7, which press against the chip from opposite sides. In practice, the number of single-claw spring plates 7 can be adjusted as needed. For example, if two or more are used, the single-claw spring plates can be arranged along one side of the chip, two adjacent sides, two opposite sides, or three sides. The side without spring plates is opposite to the direction of force. Example

[0026] like Figure 2 , 3 As shown.

[0027] The difference between this embodiment and the previous one is that the spring plate 9 used is a double-claw structure, such as... Figure 3 As shown, it consists of a bottom edge 1 welded to the heat sink 7, a transition edge 2, and two pressure claws 3. The bottom edge 1 has a concave notch 4. The transition edge 2 is connected to the bottom edge 1 and has a curved pressure claw 3 on each side. The front end of the curved pressure claw 3 has a flat plate segment 5, which abuts against the surface of the chip 6. To prevent excessive pressure from damaging the chip, a slider 8 for adjusting the elastic pressure can be fitted onto the pressure claw 3. Moving the slider 8 backward can finely adjust the distance between the pressure claw 3 and the chip, thereby reducing the clamping force. The connection state of this embodiment is as follows. Figure 2 As shown.

[0028] All parts not covered in this invention are the same as or can be implemented using existing technologies.

Claims

1. A non-welding connection method for a chip and a heat sink, characterized in that: first, one end of a spring sheet is welded to the heat sink, and the other end of the spring sheet is aligned with the position of the chip mounted on the heat sink with a set pressure and gap; second, the other end of the spring sheet is lifted to place the chip under it, and the other end of the spring sheet is released to press the chip onto the surface of the heat sink using the elastic edge, thereby completing the connection between the chip and the heat sink.

2. The method according to claim 1, characterized in that: The spring sheet serves as the connecting gold wire for the chip, providing electrical conductivity.

3. The method according to claim 1, characterized in that: The spring sheet has a single-claw structure, and each chip is fixed using at least one single-claw spring sheet.

4. The method according to claim 3, characterized in that: The single-claw structure has two or more spring plates. The single-claw spring plates are arranged along one side of the chip, two adjacent sides, two opposite sides, or three sides. The side without spring plates is opposite to the direction of force.

5. The method according to claim 1, characterized in that: The spring sheet (9) is a double claw structure, consisting of a bottom edge (1) welded to the heat sink (7), a transition edge (2) and two pressure claws (3). The bottom edge (1) has a process notch (4), the transition edge (2) is connected to the bottom edge (1) and a curved pressure claw (3) is connected to each side. The front end of the curved pressure claw (3) has a flat plate segment (5) that abuts against the surface of the chip (6).

6. The method according to claim 5, characterized in that: The pressure claw (3) is fitted with a slider (8) for adjusting the elastic pressure to prevent excessive downward pressure from damaging the chip.

7. A non-welded connection structure between a chip and a heat sink, comprising a chip (6) and a heat sink (7), characterized in that: The bottom edge (1) of the spring sheet (9) is welded to the heat sink (7), and the pressure claw (3) of the spring sheet (9) is pressed onto the chip (6), thereby realizing a non-welded connection between the chip (6) and the heat sink (7).

8. The connection structure according to claim 7, characterized in that: The spring sheet (9) is a double claw structure, consisting of a bottom edge (1) welded to the heat sink (7), a transition edge (2) and two pressure claws (3). The bottom edge (1) has a process notch (4), the transition edge (2) is connected to the bottom edge (1) and a curved pressure claw (3) is connected to each side. The front end of the curved pressure claw (3) has a flat plate segment (5) that abuts against the surface of the chip (6).

9. The connection structure according to claim 8, characterized in that: The pressure claw (3) is fitted with a slider (8) for adjusting the elastic pressure to prevent excessive downward pressure from damaging the chip.

10. The connection structure according to claim 7, characterized in that: The difference in the coefficients of thermal expansion between the chip (6) and the heat sink (7) is not less than 2, preferably not less than 5.

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