Method for eliminating marginal bubbles of DCB low-thickness product

Abstract

The invention relates to the technical field of semiconductors, in particular to a method for eliminating marginal bubbles of a DCB low-thickness product, and the method comprises the following steps: 1, bonding a polished base plate below a placement plate to obtain a sintering jig; step 2, sequentially placing a ceramic chip to be sintered and a copper foil on a placing groove in the placing plate from bottom to top, and sintering after placing is completed; and the thickness of the ceramic chip is less than 0.32 mm. The sintering jig is arranged on the surface of the conveying belt, the to-be-sintered ceramic chip and the to-be-sintered copper foil are placed in the containing groove of the containing plate, the ceramic plate with the specific thickness makes contact with the surface of the conveying belt, products obtained through final sintering are free of marginal bubbles, and therefore the qualified rate of the products is increased.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a method for eliminating bubbles at the edges of low-thickness DCB products. Background Art

[0002] DCB technology uses copper's oxygen-containing eutectic liquid to directly bond copper to ceramics. The basic principle is to introduce an appropriate amount of oxygen between copper and ceramic (alumina) before or during the bonding process. Within a certain temperature range, copper and oxygen form a Cu-O eutectic liquid, which infiltrates the copper foil to achieve the bonding of the ceramic substrate and the copper plate to generate copper aluminate and copper aluminate.

[0003] The overall thermal resistance of the product made of thin copper and thin porcelain is low, which will affect the edge heating rate of the product in the sintering furnace. Affected by the thickness characteristics of the product, the heat of the tunnel furnace is transferred to the product faster, causing the surface of the product to heat too quickly, resulting in a large number of edge bubbles on the surface of the product, reducing the product's qualification rate. Summary of the invention

[0004] The object of the present invention is to provide a method for eliminating edge bubbles of low-thickness DCB products. By placing the ceramic sheets and copper foil to be sintered in a sintering fixture, the heat transfer rate of the tunnel furnace is slowed down, and the edge bubbles of the product are avoided, thereby solving the above-mentioned problems existing in the prior art.

[0005] In order to solve the above technical problems, the present invention adopts the following solutions: A method for eliminating edge bubbles of low-thickness DCB products, comprising the following steps: Step 1: bonding the polished backing plate under the placement plate to obtain a sintering jig; Step 2: Place the ceramic sheets and copper foil to be sintered on the placement slots in the placement plate from bottom to top, and sinter after placement; The thickness of the ceramic sheet is less than 0.32 mm.

[0006] The technical concept of the present invention is: a placement plate made of silicon carbide and a pad made of quartz material are used, and the pad is bonded to the placement plate after being polished to form a sintering fixture. The ceramic pieces and copper foils to be sintered are located in the placement grooves of the placement plate. The pad blocks the heat transmitted in the tunnel furnace, slows down the speed at which the heat reaches the ceramic pieces and copper foils to be sintered from the conveyor belt, and at the same time makes the ceramic pieces and copper foils to be sintered evenly heated, thereby preventing the generation of edge bubbles in the sintered products.

[0007] Further preferably, before performing step 2, the sintering jig is placed above the conveyor belt of the tunnel furnace, and the bottom surface of the pad is in contact with the surface of the conveyor belt.

[0008] Further preferably, the two sides of the placement groove are inclined surfaces, the lowest point of the inclined surface is at half the height of the placement plate, and the angle between the inclined surface and the horizontal plane is 30° to 75°. The inclined surface facilitates the placement of the ceramic sheet to be sintered and the end of the copper foil.

[0009] Further preferably, the surface roughness of the pad after grinding is Ra3mm~5mm.

[0010] Specifically, the roughness of the backing plate is increased, thereby enhancing the bonding strength between the backing plate and the placement plate.

[0011] Further preferably, the pad is bonded to the bottom surface of the placement plate by high-temperature stepless glue.

[0012] Further preferably, the length and width of the placement plate correspond to the length and width of the pad respectively.

[0013] Further preferably, the placement plate has a length of 160 mm, a width of 200 mm, and a thickness of 15 mm to 25 mm.

[0014] Further preferably, the pad has a length of 160 mm, a width of 200 mm, and a thickness of 0.5 mm to 0.8 mm.

[0015] The thickness of the pad is between 0.5mm and 0.8mm, so that no edge bubbles are generated on the surface of the final product obtained by sintering.

[0016] Further preferably, the placement plate is made of silicon carbide, and the pad is made of quartz.

[0017] The pad is made of quartz material, which makes the pad have a large thermal resistance, slowing down the heat transfer process from the conveyor belt to the placement plate, making the heat received by the placement plate more uniform, the temperature rise and fall more slowly, and the temperature gradient more gentle. When the gentle temperature gradient acts on the sintered product, the exhaust is better and it is not easy to generate bubbles. Finally, the sintered product has no edge bubbles, thereby improving the product qualification rate.

[0018] Further preferably, during the sintering process, the sintering jig passes through seven temperature rising zones, five constant temperature zones and four temperature falling zones in sequence; The seven temperature rising zones are set at temperatures between 50°C and 640°C, 650°C and 700°C, 710°C and 800°C, 810°C and 860°C, 870°C and 930°C, 940°C and 1000°C, and 1010°C and 1060°C, respectively; The total length of the heating zone is 1700~2400mm; the time for the sintering fixture to pass through the heating zone is 9~28min; The passing time of the seven heating zones is 2min~4min, 2min~4min, 2min~4min, 2min~4min, 2min~4min, 2min~4min, 2min~4min, 2min~4min, 2min~4min; The temperature of the five constant temperature zones is set between 1065℃ and 1078℃; the total length of the constant temperature zones is 1300mm to 1700mm; the time for the sintering fixture to pass through the constant temperature zones is 12min to 20min; The four cooling zones are set at temperatures between 1010℃~1030℃, 1000℃~950℃, 890℃~940℃, and 840℃~870℃ respectively; The total length of the cooling zone is 1000mm~1400mm; the time for the sintering fixture to pass through the cooling zone is 7min~14min.

[0019] The beneficial effects of the present invention are as follows: the present invention is a method for eliminating edge bubbles of low-thickness DCB products, by arranging a sintering jig on the surface of a conveyor belt, placing ceramic sheets and copper foils to be sintered in the placement grooves of a placement plate, and ceramic sheets of a specific thickness are in contact with the surface of the conveyor belt. The pad slows down the heat transfer process from the conveyor belt to the placement plate, so that the heat received by the placement plate is more uniform, the temperature rises and falls more slowly, and the temperature gradient is more gentle. When the gentle temperature gradient acts on the sintered product, the exhaust is better and bubbles are not easily generated. Finally, the sintered product has no edge bubbles, thereby improving the qualified rate of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a working schematic diagram of the sintering jig of the present invention during sintering; Figure 2 It is a schematic diagram of the top view of the sintering fixture of the present invention; Figure 3 This is a physical picture of the product obtained after sintering Example 1 of the present invention; Figure 4 This is a physical picture of the product obtained after sintering of Comparative Example 1 of the present invention, wherein marginal bubbles exist in the product portion indicated by the box.

[0021] Reference numerals: 1 - placement plate, 10 - placement groove, 100 - inclined plane, 2 - pad, 3 - conveyor belt, 4 - ceramic sheet to be sintered, 5 - copper foil. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Example 1 Embodiment 1 of the present invention is a method for eliminating edge bubbles of a low-thickness DCB product, comprising the following steps: Step 1: After grinding the surface of the pad, use high-temperature stepless glue to bond its surface to the bottom surface of the placement plate to obtain a sintering fixture; In the sintering fixture: The two sides of the placement groove are inclined surfaces, the lowest point of the inclined surface is at half the height of the placement plate, and the angle between the inclined surface and the horizontal plane is 45°; the inclined surface is used to stably place the ceramic sheets and copper foil to be sintered.

[0024] The surface roughness of the pad after grinding is Ra3mm.

[0025] The length and width of the placement plate correspond to the length and width of the pad respectively.

[0026] The placement plate has a length of 160 mm, a width of 200 mm and a height of 15 mm.

[0027] The pad has a length of 160 mm, a width of 200 mm and a thickness of 0.5 mm.

[0028] The placement plate is made of silicon carbide, and the pad is made of quartz.

[0029] Step 2: Place the ceramic sheets and copper foil to be sintered on the placement slots in the placement plate from bottom to top, and sinter after placement; The thickness of the ceramic sheet is less than 0.32 mm.

[0030] Before step 2, place the sintering jig on the conveyor belt of the tunnel furnace, and the bottom surface of the pad is in contact with the surface of the conveyor belt. Avoid placing the pad in direct contact with the conveyor belt, so as to avoid direct transfer of heat in the tunnel furnace to the ceramic sheet and copper foil to be sintered, causing deformation of the two and the generation of edge bubbles.

[0031] During the sintering process, the sintering jig passes through seven temperature rising zones, five constant temperature zones and four temperature falling zones in sequence; The seven temperature rising zones are set at temperatures between 50°C and 640°C, 650°C and 700°C, 710°C and 800°C, 810°C and 860°C, 870°C and 930°C, 940°C and 1000°C, and 1010°C and 1060°C, respectively; The total length of the heating zone is 1700~2400mm; the time for the sintering fixture to pass through the heating zone is 9~28min; The passing time of the seven heating zones is 2min~4min, 2min~4min, 2min~4min, 2min~4min, 2min~4min, 2min~4min, 2min~4min, 2min~4min, 2min~4min; The temperature of the five constant temperature zones is set between 1065℃ and 1078℃; the total length of the constant temperature zones is 1300mm to 1700mm; the time for the sintering fixture to pass through the constant temperature zones is 12min to 20min; The four cooling zones are set at temperatures between 1010℃~1030℃, 1000℃~950℃, 890℃~940℃, and 840℃~870℃ respectively; The total length of the cooling zone is 1000mm~1400mm; the time for the sintering fixture to pass through the cooling zone is 7min~14min.

[0032] Example 2 This embodiment 2 adopts a method of eliminating bubbles at the edges of low-thickness DCB products in embodiment 1 to sinter the ceramic sheet and copper foil to be sintered.

[0033] The main differences are: The angle between the inclined plane and the horizontal plane is 75°; the inclined plane is used to stably place the ceramic sheet and copper foil to be sintered.

[0034] The surface roughness of the pad after grinding is Ra5mm.

[0035] The placement plate has a length of 160 mm, a width of 200 mm and a height of 25 mm.

[0036] The pad has a length of 160 mm, a width of 200 mm and a thickness of 0.8 mm.

[0037] Comparative Example 1 The comparative example in the present invention is sintered using the existing process.

[0038] First, the ceramic pieces and copper foil to be sintered are placed directly on the surface of the conveyor belt of the tunnel furnace from top to bottom for sintering. The heat transfer process of the tunnel furnace during sintering is: heater of the tunnel furnace → furnace of the tunnel furnace → conveyor belt of the tunnel furnace → ceramic pieces and copper foil to be sintered.

[0039] Table 1 Comparison of the number of marginal bubbles in the products sintered in Examples 1-2 and Comparative Example 1 As shown in Table 1, the final products obtained by sintering the sintering fixture in Example 1 and Example 2 according to the present invention do not have edge bubbles (such as Figure 3 As shown in the figure, the pad in the sintering jig blocks the heat transmitted in the tunnel furnace, slowing down the speed at which the heat reaches the jig and copper foil from the conveyor belt, and at the same time making the sintering jig and copper foil evenly heated, thereby preventing the edge bubbles from being generated in the sintered product. In contrast, the ceramic sheet and copper foil to be sintered in Comparative Example 1 are directly placed on the conveyor belt of the tunnel furnace, so that the heat inside the tunnel furnace is directly and quickly transferred to the ceramic sheet and copper sheet to be sintered, resulting in a large number of edge bubbles in the final sintered product (such as Figure 4 As shown), reducing the qualified rate of products.

[0040] Comparative Example 2 In this comparative example 2, a method for eliminating bubbles at the edges of low-thickness DCB products in Example 1 is used to sinter the ceramic sheet and copper foil to be sintered.

[0041] The main differences are: the length of the pad is 160 mm, the width is 200 mm, and the thickness is less than 0.5 mm.

[0042] Comparative Example 3 In this comparative example 3, a method for eliminating edge bubbles of low-thickness DCB products in Example 1 is used to sinter the ceramic sheet and copper foil to be sintered.

[0043] The main differences are: the length of the pad is 160 mm, the width is 200 mm, and the thickness is greater than 0.8 mm.

[0044] Table 2 Comparison of the number of marginal bubbles in the products sintered in Example 1 and Comparative Examples 2 and 3 It can be seen from Table 2 that when the thickness of the pad is greater than 8 mm or less than 5 mm, there are edge bubbles in the sintered product, and when the thickness of the pad is between 5 mm and 8 mm, the number of edge bubbles in the sintered product is 0. Therefore, the thickness of the pad in the sintering fixture is in the range of 5 mm to 8 mm, so that the heat blocking efficiency transmitted in the tunnel furnace and the speed of slowing down the heat from the conveyor belt to the ceramic pieces and copper foil to be sintered reach a balance, so that the ceramic pieces and copper foil to be sintered are heated evenly, and finally there are no edge bubbles in the sintered product.

[0045] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for eliminating edge bubbles of low-thickness DCB products, characterized in that: The following steps are involved: Step 1: bonding the polished backing plate under the placement plate to obtain a sintering jig; Step 2: Place the ceramic sheets and copper foil to be sintered on the placement slots in the placement plate from bottom to top, and sinter after placement; The thickness of the ceramic sheet is less than 0.32 mm.

2. A method for eliminating edge bubbles of low-thickness DCB products according to claim 1, characterized in that: Before performing step 2, the sintering jig is placed above the conveyor belt of the tunnel furnace, and the bottom surface of the pad is in contact with the surface of the conveyor belt.

3. A method for eliminating edge bubbles of low-thickness DCB products according to claim 1, characterized in that: Both sides of the placement groove are inclined surfaces, the lowest point of the inclined surface is at half the height of the placement plate, and the angle between the inclined surface and the horizontal plane is 30°~75°.

4. A method for eliminating edge bubbles of low-thickness DCB products according to claim 2, characterized in that: The surface roughness of the pad after grinding is Ra3~5mm.

5. A method for eliminating edge bubbles of low-thickness DCB products according to claim 2, characterized in that: The pad is bonded to the bottom surface of the placement plate by high-temperature stepless glue.

6. A method for eliminating edge bubbles of low-thickness DCB products according to claim 2, characterized in that: The length and width of the placement plate correspond to the length and width of the pad respectively.

7. A method for eliminating edge bubbles of low-thickness DCB products according to claim 2, characterized in that: The placement plate has a length of 160 mm, a width of 200 mm, and a thickness of 15 mm to 25 mm.

8. A method for eliminating edge bubbles of low-thickness DCB products according to claim 2, characterized in that: The pad has a length of 160 mm, a width of 200 mm, and a thickness of 0.5 mm to 0.8 mm.

9. A method for eliminating edge bubbles of low-thickness DCB products according to claim 2, characterized in that: The placement plate is made of silicon carbide, and the pad is made of quartz.

10. The method for eliminating edge bubbles of low-thickness DCB products according to claim 2, characterized in that: During the sintering process, the sintering jig passes through seven temperature rising zones, five constant temperature zones and four temperature falling zones in sequence; The seven temperature rising zones are set at temperatures between 50°C and 640°C, 650°C and 700°C, 710°C and 800°C, 810°C and 860°C, 870°C and 930°C, 940°C and 1000°C, and 1010°C and 1060°C, respectively; The total length of the heating zone is 1700~2400mm; the time for the sintering fixture to pass through the heating zone is 9~28min; The passing time of the seven heating zones is 2min~4min, 2min~4min, 2min~4min, 2min ~4min, 2min ~4min, 2min~4min, 2min~4min, 2min~4min; The temperature of the five constant temperature zones is set between 1065℃ and 1078℃; the total length of the constant temperature zones is 1300mm to 1700mm; the time for the sintering fixture to pass through the constant temperature zones is 12min to 20min; The four cooling zones are set at temperatures between 1010℃~1030℃, 1000℃~950℃, 890℃~940℃, and 840℃~870℃ respectively; The total length of the cooling zone is 1000mm~1400mm; the time for the sintering fixture to pass through the cooling zone is 7min~14min.

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