Brazing method for multi-tooth-position high-density lead frame
By using cooked porcelain multi-tooth positioning blocks and cast porcelain belt technology, the positioning error and cost problems of multi-tooth position high-density lead frame brazing are solved, and higher production efficiency and lower product scrapping rate are achieved.
Patent Information
- Application Number
- CN202411922917.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-25
- Publication Date
- 2025-03-21
AI Technical Summary
When brazing a multi-tooth high-density lead frame, the expansion coefficients of metal positioning teeth and lead frames are different, and they are prone to deviation and deformation. The prior art uses an optical curve grinder to make positioning teeth, which is costly and poorly flexible.
Cooked porcelain multi-tooth positioning blocks are used to drill, fill and print layer by layer through casting porcelain belts, and positioning teeth are made by laser processing. Manual intervention of microscope ensures accurate positioning, and then brazing is performed.
Since the porcelain body is the same as the positioning teeth and the expansion coefficient is the same, it reduces deformation errors during brazing, reduces product scrap rate and production costs, and improves the flexibility of positioning teeth spacing and low adjustment costs.
Smart Images
Figure CN119658046A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of chip packaging, and in particular to a soldering method for a multi-tooth position high-density lead frame. Background Art
[0002] "Lead frame" refers to a component that supports and fixes semiconductor chips (semiconductor elements) in semiconductor packages such as ICs and LSIs, and connects to external wiring through multiple external connection terminals "external leads" that extend from the package like centipede legs. Lead frames (leads) are generally made of long thin plates made of iron-nickel-cobalt alloy or silver-copper alloy materials. These long thin plates are transported in sequence and processed by precision stamping (punching, drawing, bending). In this way, they are formed into "chip pads" that support and fix semiconductor chips (semiconductor elements), "inner leads" that are wired to semiconductor elements, and "external leads" that connect to external wiring. In addition to mechanical processing, the lead frame manufacturing process also includes surface treatment processes such as etching and plating. Lead frames can be used not only for integrated circuit packages such as ICs and LSIs, but also for discrete semiconductors, photocouplers, LEDs, etc. All of these use wire bonding as a method of internally connecting the electrodes and inner leads of semiconductor elements.
[0003] In recent years, with the miniaturization of packaged electronic components and the high density of electronic circuits, lead frames and their connections require more stringent precision, and multi-tooth high-density lead frames have emerged. However, when brazing multi-tooth high-density lead frames, either metal positioning teeth are used or they are directly brazed without positioning teeth. When metal positioning teeth are used for brazing, due to the different expansion coefficients of the metal positioning teeth and the lead frame, it is easy to offset and deform, and it is difficult to position and weld; if the positioning teeth are not used for direct brazing, the probability of offset and poor positioning is higher. In addition, the existing technology uses an optical curve grinder to make positioning teeth. Due to the fixed size, the cost is expensive, and it is easy to stick to metal parts during brazing, resulting in a low scrap yield rate and poor flexibility. Summary of the invention
[0004] The invention provides a method for preparing a ceramic multi-tooth positioning block for a lead frame, which solves the problems of high manufacturing cost of the existing positioning block and easy adhesion with metal parts during brazing.
[0005] In order to solve the above technical problems, the technical solution of the present invention is: The present invention provides a soldering method for a multi-tooth high-density lead frame, comprising the following steps: (1) Place the ceramic positioning block and lead frame into the base plate in sequence, and manually intervene under a microscope to ensure that all pins of the lead frame are located in the positioning teeth of the ceramic positioning block; (2) Place the silver-copper solder sheet on top of the lead frame pin, then use a suction cup to place the porcelain body into the base plate, and place the brazing fixture fixing plate on top of the porcelain body; (3) Place the silver-copper solder sheet and metal heat sink into the fixed plate, cover the cover plate, add a counterweight on top of the cover plate, and then put it into the brazing furnace for brazing.
[0006] Wherein, in step (1), the cooked porcelain positioning block is made by the following preparation method: (1) Use tape-cast raw porcelain tape to perform layer-by-layer punching, hole filling and printing according to the metallization wiring requirements of the product; (2) Place the green ceramic sheet that has been filled with metallized patterns and printed into the designated position of the laser machine, perform laser scanning and punching on the surface of the green ceramic sheet, and obtain positioning teeth in the laser scanning area after the laser scanning treatment. Then, the punching part of the green sheet and the positioning block forming part are processed according to the required dimensions of the product. (3) The processed multi-layer green sheet is subjected to isostatic pressing, and then pre-cut by a hot cutter, and then sent to a sintering furnace to obtain cooked porcelain. After surface treatment, the product is cracked into single products, and the positioning blocks are sent to the brazing workshop for use in brazing processes.
[0007] Wherein, the tape-cast green porcelain tape is made by the following preparation method: (1) Ball milling: Ceramic powder is mixed with solvents, binders, etc., and mixed and refined by a ball mill to obtain a uniform ceramic slurry; (2) Casting: Use a casting machine to evenly coat the ball-milled slurry on the carrier to form a continuous film with a thickness of 0.1-0.4 mm.
[0008] The solvent is composed of isopropanol and ethanol in a volume ratio of 2:1, the mass volume ratio of the ceramic powder to the solvent is (0.8-1.2):1, and the adhesive is made by mixing the following raw materials in parts by weight: 18-40 parts of polyacrylic acid amine salt, 18-40 parts of polyvinyl alcohol, 40-70 parts of ethanol, 3-9 parts of propylene glycol, and 3-9 parts of polyethylene glycol. The mass volume ratio of the adhesive to the ceramic powder is (0.05-0.1):1.
[0009] The punching in step (1) is specifically to use laser punching technology or punching technology to make the required holes on the ceramic sheet.
[0010] The hole filling in step (1) specifically involves filling the punched holes with metal paste to form a circuit or structure.
[0011] The printing in step (1) is specifically to print the circuit pattern on the ceramic sheet using screen printing or other printing techniques.
[0012] Wherein, step (2) further includes a slurry coating step, specifically, coating the side wall of the ceramic sheet with a layer of slurry to achieve conduction.
[0013] Wherein, after sintering, step (3) further includes the step of electroplating the sintered ceramic substrate to improve its conductivity or add a protective layer.
[0014] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects: (1) The ceramic body and the positioning teeth in the present invention are made of the same material and have the same expansion coefficient. During brazing, there will be no errors such as deformation and dislocation due to temperature changes, which reduces the scrap rate of the product and reduces the production cost.
[0015] (2) The present invention uses a ceramic block as the positioning device, and the positioning teeth are made by laser machining, which is convenient to manufacture and low in cost. In addition, compared with the existing positioning devices, the spacing between the positioning teeth can be adjusted flexibly and the adjustment cost is low. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 This is a front view structural schematic diagram of the positioning block of the present invention; Figure 2 It is a schematic diagram of the assembly structure of the positioning block and the lead frame of the present invention.
[0017] In the figure, 1. Porcelain positioning block, 2. Lead frame, 3. Porcelain body DETAILED DESCRIPTION
[0018] The following embodiments are provided for a better understanding of the present invention, but are not limited to the best mode of implementation, and do not limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention. Example 1
[0019] This embodiment provides a soldering method for a multi-tooth high-density lead frame 2, comprising the following steps: (1) Place the ceramic positioning block 1 and the lead frame 2 into the base plate in sequence, and manually intervene under a microscope to ensure that all the pins of the lead frame 2 are located in the positioning teeth of the ceramic positioning block 1; (2) Place the silver-copper solder sheet on top of the lead frame 2 pin, then use the suction cup to place the ceramic body 3 on the bottom plate, and place the soldering fixture fixing plate on top of the ceramic body 3 (such as Figure 1 , Figure 2 shown); (3) Place the silver-copper solder sheet and metal heat sink into the fixed plate, cover the cover plate, add a counterweight on top of the cover plate, and then put it into the brazing furnace for brazing.
[0020] The ceramic positioning block 1 of this embodiment is made by the following preparation method: (1) Ball milling: Ceramic powder is mixed with a solvent, a binder, etc., and mixed and refined by a ball mill to obtain a uniform ceramic slurry; the solvent is composed of isopropanol and ethanol in a volume ratio of 2:1, the mass volume ratio of the ceramic powder to the solvent is 1.0:1, and the binder is made by mixing the following raw materials in parts by weight: 30 parts of polyacrylic acid amine salt, 30 parts of polyvinyl alcohol, 55 parts of ethanol, 6 parts of glycerol, and 6 parts of polyethylene glycol, and the mass volume ratio of the binder to the ceramic powder is 0.08:1; (2) Casting: Use a casting machine to evenly coat the ball-milled slurry on the carrier to form a continuous film with a thickness of 0.2 mm; (3) Using cast raw ceramic tape, laser drilling technology is used to perform layer-by-layer drilling, hole filling and printing according to the metallization wiring requirements of the product; hole filling specifically involves filling metal slurry at the punched position to form a circuit or structure, and printing specifically involves printing a circuit pattern on a ceramic sheet using screen printing or other printing technology; (4) Place the green ceramic with metallized pattern filling and printing in the designated position of the laser machine, perform laser scanning and punching on the surface of the green ceramic, and obtain positioning teeth in the laser scanning area after the laser scanning treatment. Then, the punching part and the positioning block forming part of the green ceramic sheet are processed according to the required dimensions of the product. Then, a layer of slurry is applied to the side wall of the ceramic sheet to achieve conduction. (5) The processed multi-layer green sheet is subjected to isostatic pressing, and then pre-cut by a hot cutter, and then sent to a sintering furnace to obtain cooked porcelain. The product is cracked into single products after surface treatment. The sintered ceramic substrate is electroplated to improve its conductivity or add a protective layer. The positioning block is sent to the brazing workshop for use in brazing processes. Example 2
[0021] This embodiment provides a soldering method for a multi-tooth high-density lead frame, comprising the following steps: (1) Place the ceramic positioning block 1 and the lead frame into the base plate in sequence, and manually intervene under a microscope to ensure that all pins of the lead frame are located in the positioning teeth of the ceramic positioning block 1; (2) Place the silver-copper solder sheet on top of the lead frame pin, then use a suction cup to place the ceramic body 3 on the bottom plate, and place the soldering fixture fixing plate on top of the ceramic body 3; (3) Place the silver-copper solder sheet and metal heat sink into the fixed plate, cover the cover plate, add a counterweight on top of the cover plate, and then put it into the brazing furnace for brazing.
[0022] The ceramic positioning block 1 of this embodiment is made by the following preparation method: (1) Ball milling: Ceramic powder is mixed with a solvent, a binder, etc., and mixed and refined by a ball mill to obtain a uniform ceramic slurry; the solvent is composed of isopropanol and ethanol in a volume ratio of 2:1, the mass volume ratio of the ceramic powder to the solvent is 0.8:1, and the binder is made by mixing the following raw materials in parts by weight: 18 parts of polyacrylic acid amine salt, 40 parts of polyvinyl alcohol, 40 parts of ethanol, 9 parts of glycerol, and 9 parts of polyethylene glycol, and the mass volume ratio of the binder to the ceramic powder is 0.1:1; (2) Casting: Use a casting machine to evenly coat the ball-milled slurry on the carrier to form a continuous film with a thickness of 0.1 mm; (3) Using cast raw ceramic tape, punching, filling and printing are performed layer by layer according to the metallization wiring requirements of the product using punching technology; filling is to fill metal paste at the punched position to form a circuit or structure, and printing is to print the circuit pattern on the ceramic sheet using screen printing or other printing technology; (4) Place the green ceramic with metallized pattern filling and printing in the designated position of the laser machine, perform laser scanning and punching on the surface of the green ceramic, and obtain positioning teeth in the laser scanning area after the laser scanning treatment. Then, the punching part and the positioning block forming part of the green ceramic sheet are processed according to the required dimensions of the product. Then, a layer of slurry is applied to the side wall of the ceramic sheet to achieve conduction. (5) The processed multi-layer green sheet is subjected to isostatic pressing, and then pre-cut by a hot cutter, and then sent to a sintering furnace to obtain cooked porcelain. The product is cracked into single products after surface treatment to improve its conductivity or add a protective layer. The positioning blocks are sent to the brazing workshop for use in brazing processes. Example 3
[0023] This embodiment provides a soldering method for a multi-tooth high-density lead frame, comprising the following steps: (1) Place the ceramic positioning block 1 and the lead frame into the base plate in sequence, and manually intervene under a microscope to ensure that all pins of the lead frame are located in the positioning teeth of the ceramic positioning block 1; (2) Place the silver-copper solder sheet on top of the lead frame pin, then use a suction cup to place the ceramic body 3 on the bottom plate, and place the soldering fixture fixing plate on top of the ceramic body 3; (3) Place the silver-copper solder sheet and metal heat sink into the fixed plate, cover the cover plate, add a counterweight on top of the cover plate, and then put it into the brazing furnace for brazing.
[0024] The ceramic positioning block 1 of this embodiment is made by the following preparation method: (1) Ball milling: Ceramic powder is mixed with a solvent, a binder, etc., and mixed and refined by a ball mill to obtain a uniform ceramic slurry; the solvent is composed of isopropanol and ethanol in a volume ratio of 2:1, the mass volume ratio of the ceramic powder to the solvent is 1.2:1, and the binder is made by mixing the following raw materials in parts by weight: 40 parts of polyacrylic acid amine salt, 18 parts of polyvinyl alcohol, 70 parts of ethanol, 3 parts of glycerol, and 3 parts of polyethylene glycol, and the mass volume ratio of the binder to the ceramic powder is 0.05:1; (2) Casting: Use a casting machine to evenly coat the ball-milled slurry on the carrier to form a continuous film with a thickness of 0.4 mm; (3) Using cast raw ceramic tape, laser punching technology or punching technology is used to perform layer-by-layer punching, hole filling and printing according to the metallization wiring requirements of the product; hole filling specifically involves filling metal slurry at the punched position to form a circuit or structure, and printing specifically involves printing a circuit pattern on a ceramic sheet using screen printing or other printing technology; (4) Place the green ceramic with metallized pattern filling and printing in the designated position of the laser machine, perform laser scanning and punching on the surface of the green ceramic, and obtain positioning teeth in the laser scanning area after the laser scanning treatment. Then, the punching part and the positioning block forming part of the green ceramic sheet are processed according to the required dimensions of the product. Then, a layer of slurry is applied to the side wall of the ceramic sheet to achieve conduction. (5) The processed multi-layer green sheet is subjected to isostatic pressing, and then pre-cut by a hot cutter, and then sent to a sintering furnace to obtain cooked porcelain. The product is cracked into single products after surface treatment. The sintered ceramic substrate is electroplated to improve its conductivity or add a protective layer. The positioning block is sent to the brazing workshop for use in brazing processes.
[0025] Although the embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and purpose of the present invention. The protection scope of the present invention is defined by the claims and their equivalent technical solutions.
Claims
1. A method for soldering a multi-tooth high-density lead frame, characterized in that The steps include: (1) Place the ceramic positioning block and lead frame into the base plate in sequence, and manually intervene under a microscope to ensure that all pins of the lead frame are located in the positioning teeth of the ceramic positioning block; (2) Place the silver-copper solder sheet on top of the lead frame pin, then use a suction cup to place the porcelain body into the base plate, and place the brazing fixture fixing plate on top of the porcelain body; (3) Place the silver-copper solder sheet and metal heat sink into the fixed plate, cover the cover plate, add a counterweight on top of the cover plate, and then put it into the brazing furnace for brazing.
2. The method for soldering a multi-tooth high-density lead frame according to claim 1, characterized in that: In step (1), the cooked porcelain positioning block is made by the following preparation method: (1) Use tape-cast raw porcelain tape to perform layer-by-layer punching, hole filling and printing according to the metallization wiring requirements of the product; (2) Place the green ceramic sheet that has been filled with metallized patterns and printed into the designated position of the laser machine, perform laser scanning and punching on the surface of the green ceramic sheet, and obtain positioning teeth in the laser scanning area after the laser scanning treatment. Then, the punching part of the green sheet and the positioning block forming part are processed according to the required dimensions of the product. (3) The processed multi-layer green sheet is subjected to isostatic pressing, and then pre-cut by a hot cutter, and then sent to a sintering furnace to obtain cooked porcelain. After surface treatment, the product is cracked into single products, and the positioning blocks are sent to the brazing workshop for use in brazing processes.
3. The method for soldering a multi-tooth high-density lead frame according to claim 2, characterized in that: The tape-cast green porcelain tape is made by the following preparation method: (1) Ball milling: Ceramic powder is mixed with solvents, binders, etc., and mixed and refined by a ball mill to obtain a uniform ceramic slurry; (2) Casting: Use a casting machine to evenly coat the ball-milled slurry on the carrier to form a continuous film with a thickness of 0.1-0.4 mm.
4. The method for soldering a multi-tooth high-density lead frame according to claim 2, characterized in that: The punching in step (1) specifically involves making the required holes on the ceramic sheet using laser punching technology or punching technology.
5. The method for soldering a multi-tooth high-density lead frame according to claim 2, characterized in that: The hole filling in step (1) specifically involves filling the punched hole with metal paste to form a circuit or structure.
6. A soldering method for a multi-tooth high-density lead frame according to claim 2, characterized in that: The printing in step (1) specifically involves printing a circuit pattern on the ceramic sheet using screen printing or other printing techniques.
7. The method for soldering a multi-tooth high-density lead frame according to claim 2, characterized in that: The step (2) also includes a slurry coating step, specifically, coating the side wall of the ceramic sheet with a layer of slurry to achieve conduction.
8. The method for soldering a multi-tooth high-density lead frame according to claim 2, characterized in that: After sintering, step (3) further includes the step of electroplating the sintered ceramic substrate to improve its conductivity or add a protective layer.