Chip ceramic packaging structure with flat heat sink

Abstract

The utility model discloses a chip ceramic packaging structure with a flat plate heat sink. The chip ceramic packaging structure comprises a ceramic base and the flat plate heat sink, the ceramic base is of a through cavity structure, the ceramic base is welded to the bottom of the ceramic base through welding flux, and the chip is arranged in a through cavity and connected to a chip bonding area in the center of the flat plate heat sink. And the top of the ceramic base is welded with the metal cover plate through the sealing ring. A concentric-square-shaped groove is formed in the position, located on the outer side of the core bonding area and close to the inner side face of the through cavity structure, of the face, making contact with the ceramic base, of the flat plate heat sink, so that when the flat plate heat sink and the ceramic base are welded, redundant welding flux can be dragged into the concentric-square-shaped groove in sequence, and the redundant welding flux is accumulated in the groove after being cooled; the welding flux is effectively prevented from flowing towards the middle of the flat plate heat sink in an uncontrolled manner during welding, so that the flatness of connection between the flat plate heat sink and the ceramic base after welding is ensured, the welding flux is prevented from flowing to a core bonding area, namely, the flatness of the core bonding area is ensured, and the packaging qualification rate of products is improved.

Description

Technical Field

[0001] The utility model relates to a chip packaging structure, in particular to a chip ceramic packaging structure. Background Art

[0002] Ceramic packaging refers to a packaging method that encapsulates electronic components in ceramic materials to achieve dustproof, moisture-proof, corrosion-resistant, and isolation functions. Since ceramic materials have a high melting point and good thermal conductivity, ceramic-packaged devices can withstand long-term operation in high-temperature environments. Ceramic materials have high hardness and high compressive strength, which can effectively protect internal components from mechanical damage. Ceramic materials are not easily corroded by chemicals and can resist erosion by acidic and alkaline environments and other corrosive substances.

[0003] The ceramic packaging process requires multiple high-temperature heating and pressing, and has high requirements for temperature and pressure control, so the production is relatively difficult. The metallization treatment in the packaging process plays an important role in the performance of ceramic packaging devices. Uneven metal coating or poor welding may cause damage to internal components and put them in poor working condition.

[0004] For the packaging structure of some active devices, due to their high power and high heat generation, a heat sink structure is usually required when packaging such electronic devices. In the existing production process, it is found that the packaging structure with a heat sink has unevenness after the structure is electroplated with nickel and gold in the subsequent packaging process, which affects the product appearance and the mechanical performance of the chip connection in the subsequent process, causing problems with the product qualification rate. Summary of the invention

[0005] Purpose of the invention: In view of the above-mentioned prior art, a chip ceramic packaging structure with a flat heat sink is proposed to solve the problem of low product qualification rate caused by uneven welding of the flat heat sink.

[0006] Technical solution: A chip ceramic packaging structure with a flat plate heat sink, comprising a ceramic base and a flat plate heat sink; the ceramic base is a through-cavity structure, the ceramic base is welded to the bottom of the ceramic base by solder, the chip is arranged in the through-cavity, and is connected to the core bonding area in the center of the flat plate heat sink by welding or surface mounting; the top of the ceramic base is welded to the metal cover plate by a sealing ring; wherein, on the side of the flat plate heat sink that contacts the ceramic base, a return groove is provided at a position outside the core bonding area and close to the inner side of the through-cavity structure.

[0007] Furthermore, the flat plate heat sink is a metal flat plate heat sink or a ceramic flat plate heat sink.

[0008] Furthermore, the flat plate heat sink is a tungsten copper flat plate heat sink.

[0009] Furthermore, when the flat plate heat sink is a ceramic flat plate heat sink, the solder is gold-tin solder.

[0010] Beneficial effect: The utility model provides a chip ceramic packaging structure with a flat plate heat sink, and a pre-engraved return groove is formed on the outer side of the core bonding area of ​​the flat plate heat sink. The return groove is adjacent to the inner side of the through-cavity structure of the ceramic base, so that when the flat plate heat sink and the ceramic base are welded, excess solder can be orderly drawn into the return groove and accumulated in the groove after cooling, effectively preventing the solder that becomes liquid after being heated from flowing uncontrollably to the middle of the flat plate heat sink.

[0011] The structure for preventing solder from flowing excessively is adopted. Firstly, the solder thickness at various positions around the soldering process is ensured to be always consistent, thereby ensuring the overall flatness of the connection between the flat heat sink and the ceramic base after welding; secondly, the transitional solder is retained in the return groove on the outside, avoiding flowing to the core bonding area, that is, ensuring the flatness of the core bonding area, thereby avoiding the reliability of the chip connection being affected due to the presence of solder in the core bonding area when welding or labeling the chip in the subsequent process, and finally improving the packaging qualification rate of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic cross-sectional structure diagram of the chip ceramic packaging structure of the utility model;

[0013] Figure 2 This is a schematic diagram of the top view of the chip ceramic packaging structure of the utility model;

[0014] Figure 3 Schematic diagram of the structure and dimensions of the flat plate heat sink in the embodiment. DETAILED DESCRIPTION

[0015] The present invention will be further explained below in conjunction with the accompanying drawings. Example

[0016] like Figure 1 , Figure 2 As shown, a chip ceramic packaging structure with a flat heat sink includes a ceramic base 1-1 and a flat heat sink 1-3. The ceramic base 1-1 is a through-cavity structure. The ceramic base 1-1 is welded to the bottom of the ceramic base 1-1 by solder 1-2. The chip is arranged in the through-cavity and connected to the core bonding area in the center of the flat heat sink 1-3 by welding or surface mounting. The top of the ceramic base 1-1 is welded to the metal cover plate by a sealing ring 1-5, so that the connection has good airtightness. The metal cover plate is usually selected from a low CTE Kovar alloy or Invar alloy.

[0017] The flat plate heat sink 1-3 is a tungsten copper flat plate heat sink, and a return groove 1-4 is provided on the side of the flat plate heat sink 1-3 that contacts the ceramic base 1-1, which is located outside the core bonding area and close to the inner side of the through cavity structure. The ceramic base 1-1 is an alumina ceramic base, and the solder 1-2 uses Ag72Cu28 solder.

[0018] The following is an explanation of the product model SMD1A. The ceramic base 1-1 of the SMD1A product is prepared using a normal production process, such as Figure 3 As shown, the overall dimensions of the flat heat sink 1-3 are 10.47mm×9.53mm, and the return groove 1-4 is 1.00mm away from the edge. Through ANSYS simulation, it is determined that the total thickness of the flat heat sink is 0.4mm, the etching depth of the return groove 1-4 is 0.12mm, and the etching depth width of the return groove 1-4 is 0.24mm. The flat heat sink is processed with a round chamfer of R0.40mm, and the return groove 1-4 is also processed with a round chamfer of R0.20mm. The overall processing accuracy requirement is ±0.03mm. Example

[0019] The difference from Example 1 is that the flat plate heat sink 1-3 is a ceramic flat plate heat sink, and the solder 1-2 is gold-tin solder.

[0020] The brazing temperature of gold-tin solder is only 20 to 30°C higher than its melting point. Because the gold-tin alloy is eutectic, the alloy melts faster and solidifies faster, further reducing the problem of solder transition flow during the brazing process.

[0021] In addition, since the ceramic heat sink has good wettability and the gold-tin alloy and the gold-plated layer have similar compositions, the degree of dissolution of the very thin plating layer by diffusion is very low, so migration is not easy to occur when the packaging structure is subsequently electroplated with nickel and gold.

[0022] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A chip ceramic packaging structure with a flat heat sink, characterized in that: The invention comprises a ceramic base (1-1) and a flat plate heat sink (1-3); the ceramic base (1-1) is a through-cavity structure, the ceramic base (1-1) is welded to the bottom of the ceramic base (1-1) by solder (1-2), a chip is arranged in the through-cavity and connected to a core bonding area in the center of the flat plate heat sink (1-3) by welding or surface mounting; the top of the ceramic base (1-1) is welded to a metal cover plate by a sealing ring (1-5); wherein a return groove (1-4) is provided on a surface of the flat plate heat sink (1-3) that contacts the ceramic base (1-1) and is located outside the core bonding area and close to the inner side surface of the through-cavity structure.

2. The chip ceramic packaging structure with a flat heat sink according to claim 1, characterized in that: The flat plate heat sink (1-3) is a metal flat plate heat sink or a ceramic flat plate heat sink.

3. The chip ceramic packaging structure with a flat heat sink according to claim 2, characterized in that: The flat plate heat sink (1-3) is a tungsten copper flat plate heat sink.

4. The chip ceramic packaging structure with a flat heat sink according to claim 2, characterized in that: When the flat plate heat sink (1-3) is a ceramic flat plate heat sink, the solder (1-2) is a gold-tin solder.

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