Bonding process for multilayer wiring ceramic circuit board

Abstract

The invention discloses a multi-layer wiring ceramic circuit board bonding process, which comprises the following steps of: completing processing of a bottom layer circuit of a single-layer circuit board, and electroplating and thickening a metal bonding pad for multi-layer welding on the basis of bottom layer metal; printing ink on the bonding surface, polishing the ink and the thickening layer to be in an equal-height state by adopting a polishing process, exposing and developing the ink, and then baking and curing; carrying out surface metallization treatment on the cured ceramic circuit board; performing electron beam plating of a gold-tin solder on the metal surface of the thickening layer on the metallized ceramic substrate; the bonding surfaces of different single-layer circuit boards subjected to solder thickening are face-to-face, high-precision alignment stacking and fixing are carried out through equipment, and reflow soldering is carried out at the highest temperature of 300 DEG C. The method has the advantages that an electroplating thickening mode is matched with an ink screen printing mode, the insulation effect between different circuits can be effectively achieved, and the problem of welding flux flowing short circuit possibly caused in the subsequent welding process is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of ceramic substrates, and in particular to a bonding process for a multi-layer wiring ceramic circuit board. Background Art

[0002] As electronic technology is gradually deepened in various application fields, the high integration of circuit boards has become an inevitable trend. At present, the basic method for preparing multi-layer ceramics is to stack multi-layer thin films + multi-layer AlN substrates together after positioning and fixing, and use ceramic powder to insulate and connect each layer of circuit boards, and realize ceramic integration under high-temperature sintering conditions. HTCC / LTCC products are common in the market.

[0003] China invention patent authorization announcement number CN102110616B discloses a method for realizing thin-film multilayer wiring on LTCC substrate, including the following steps: (1) substrate interface treatment; (2) substrate cleaning; (3) sputtering adhesion layer on substrate; (4) photolithography guide strip version; (5) electroplating guide strip; (6) photolithography through hole column version; (7) electroplating through hole column; (8) removing electroplating mold; (9) photolithography guide strip reverse version; (10) etching adhesion layer; (11) dielectric film processing; (12) repeating steps (3) to (11) to make LTCC substrate with thin-film multilayer wiring interconnected by through hole columns. However, LTCC adopts wet etching, which is difficult to control during the production process. It is easy to lateral drilling, resulting in line shedding, disconnection and other phenomena. It is difficult to ensure that the line accuracy reaches 20μm / 20μm, and the yield is low. In addition, the shrinkage rate of HTCC substrate has high requirements on sintering process conditions, and the through holes on its substrate are prone to displacement. .

[0004] Chinese invention patent publication number CN114496809A discloses a method for manufacturing thin-film multilayer wiring on HTCC substrates, the main steps of which are: S1, providing an HTCC substrate, polishing, cleaning and high-temperature vacuum heat treatment of the HTCC substrate; S2, forming a first metal wiring layer on the surface of the HTCC substrate; S3, forming a first insulating dielectric layer on the surface of the first metal wiring layer; S4, repeating steps S2-S3 at least 4 times to complete no less than 5 layers of thin-film multilayer wiring on the surface of the HTCC substrate. This method also uses wet etching, which is difficult to control during the manufacturing process. Summary of the invention

[0005] The technical problem to be solved by the present invention is that the influence of the existing high-temperature sintering process on the shrinkage rate of ceramics causes the through holes to be easily displaced, and for this purpose, a multi-layer wiring ceramic circuit board bonding process is provided.

[0006] The technical solution of the present invention is: a multi-layer wiring ceramic circuit board bonding process, comprising the following steps: completing the bottom line processing of the single-layer circuit board, electroplating and thickening the metal pad used for multi-layer welding on the bottom metal basis; using ink silk screen printing technology to print ink on the bonding surface, and using a polishing process to grind the ink and the thickened layer to the same height state, and then treating the ink with a weak alkaline solution, the height of the ink will be uniformly reduced, so that its height is lower than the metal pad, exposing the ink to development, and post-baking and curing; performing surface metallization treatment on the cured ceramic circuit board; electron beam-plating gold-tin solder on the thickened layer metal surface on the metallized ceramic substrate; placing the bonding surfaces of different single-layer circuit boards that have completed solder thickening face to face, stacking and fixing them through high-precision alignment equipment, and performing reflow soldering at a maximum temperature of 300°C. After cooling, the bonding of the multi-layer wiring ceramic circuit board is completed.

[0007] In the above scheme, the weak alkaline solution is a 1wt% Na2CO3 solution.

[0008] The height of the metal pad thickened by electroplating in the above solution is 20 μm-30 μm.

[0009] The thickness of the gold-tin solder in the above solution is 5 μm-15 μm.

[0010] The beneficial effects of the present invention are that the electroplating thickening method is combined with the ink screen printing method, and the ink processing is realized by the development method, which can effectively realize the insulation effect between different circuits and avoid the problem of solder flow short circuit that may be caused by the subsequent welding process; the 300℃ reflow soldering process is used, and under this low temperature condition, the deformation and shrinkage of the ceramic substrate due to high temperature sintering can be avoided, and the problem of welding misalignment is solved. The yield rate of bonding of multi-layer wiring ceramic circuit boards is improved, and the difficulty of operation is greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a photo of the multilayer wiring ceramic circuit board of the present invention; Figure 2 It is a process flow chart of ink treatment of the present invention. DETAILED DESCRIPTION

[0012] The technical solutions in the embodiments of the present invention are described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments by ordinary technicians in this field without creative work are within the protection scope of the present invention.

[0013] like Figure 1 As shown, a multi-layer wiring ceramic circuit board bonding process includes the following steps: Step 1: Complete the bottom layer circuit processing of the single-layer circuit board, and electroplate and thicken the metal pads used for multi-layer welding on the basis of the bottom metal, with the thickening height being 20μm-30μm, such as 20μm, 25μm or 30μm; Step 2: Use ink screen printing technology to print ink on the bonding surface, and use a polishing process to grind the ink and the thickened layer to the same height, then expose the ink to development and post-bake to cure; this makes the ink lower than the metal film, reducing the difficulty of the welding process; Step 3, performing surface metallization treatment on the cured ceramic circuit board; Step 4: Electron beam-plating gold-tin solder on the thickened metal surface of the ceramic substrate after the metallization treatment, the solder thickness is about 5 μm-15 μm, such as 5 μm, 10 μm or 15 μm; Step 5: Place the bonding surfaces of the above-mentioned different single-layer circuit boards that have been thickened with solder face to face, stack them with high-precision alignment equipment, and fix them. Perform reflow soldering at a maximum temperature of 300°C. After cooling, the bonding of the multi-layer wiring ceramic circuit board is completed.

[0014] like Figure 2 As shown, after the solder mask screen printing is completed, the ink will cover the entire metal layer, and after grinding, the ink height and the metal reach a micron-level height difference. At this time, if the seal is directly performed, if the ink height exceeds the metal, there will be a risk of cold welding. The usual practice is to thicken the metal, and the process is cumbersome. In the present invention, after the grinding process, the ink is treated with a weak alkaline solution, and the thickness of the ink will be uniformly reduced. The specific weak alkaline solution is preferably a 1wt% Na2CO3 solution, and the overall height is lower than the metal pad. After treatment, the metal pad can achieve parallel sealing, which reduces the difficulty of welding.

Claims

1. A multi-layer wiring ceramic circuit board bonding process, characterized in that: The following steps are involved: Complete the bottom layer circuit processing of the single-layer circuit board, and electroplate and thicken the metal pads used for multi-layer welding on the basis of the bottom metal; Use ink silk screen printing technology to print ink on the bonding surface, and use a polishing process to grind the ink and the thickened layer to the same height. Then use a weak alkaline solution to treat the ink, and the height of the ink will be evenly reduced, making it lower than the metal pad. The ink is exposed to light, developed, and then baked for curing; the cured ceramic circuit board is surface metallized; the thickened metal surface of the ceramic substrate after the metallization treatment is electron beam plated with gold-tin solder; the bonding surfaces of different single-layer circuit boards that have been thickened with solder are placed face to face, stacked and fixed with high-precision alignment equipment, and reflow soldering is performed at a maximum temperature of 300°C. After cooling, the bonding of the multi-layer wiring ceramic circuit board is completed.

2. A multi-layer wiring ceramic circuit board bonding process as claimed in claim 1, characterized in that: The weak alkaline solution is a 1wt% Na2CO3 solution.

3. A multi-layer wiring ceramic circuit board bonding process as claimed in claim 1, characterized in that: The height of the metal pad thickened by electroplating is 20 μm-30 μm.

4. A multi-layer wiring ceramic circuit board bonding process as claimed in claim 1, characterized in that: The thickness of the gold-tin solder is 5 μm-15 μm.

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