A method for selectively roughening a ceramic copper clad plate

Abstract

This invention discloses a selective roughening method for ceramic copper-clad laminates, comprising the following preparation steps: S1 printing an active solder layer between ceramic and copper foil; S2 preparing the ceramic copper-clad laminate; S3 etching copper onto the sintered ceramic copper-clad laminate; S4 removing unwanted solder layers; S5 cleaning, roughening, cleaning, acid washing, cleaning, immersion, and drying the patterned ceramic copper-clad laminate according to the following process, and filling it with nano-silicon and organosilane; S6 printing a thermosetting wet film to expose the area to be surface treated; S7 removing the surface roughening structure; S8 finally, subjecting the ceramic copper-clad laminate to nickel plating, chemical silvering, and then stripping to form the final structure. Compared with the prior art, this invention has the following beneficial effects: effectively avoiding the problem of solder voids caused by surface roughening pits, good surface weldability, and the concave structure of the welding area effectively prevents solder overflow during the welding process and reduces micropores in the chemical silver plating layer.

Description

Technical Field

[0001] This invention relates to the field of ceramic copper-clad laminate technology, and specifically to a selective roughening method for ceramic copper-clad laminates. Background Technology

[0002] Gel potting is commonly used in power devices. The adhesive is typically in the form of silicone gel, used to protect the device from vibration and shock, provide waterproofing and moisture protection, and achieve a seal. Compared to molding, potting is more expensive. Molding, on the other hand, uses a transfer molding process, evolved from wet layup and injection molding, and is a method for molding thermosetting plastics. It is low-cost and efficient, but its thermal shock resistance is relatively poor, and the resin edges are prone to cracking against the ceramic backing.

[0003] Currently, the bonding strength of epoxy resin can be improved by adding and optimizing coupling agents in the resin to form chemical bonds with inorganic media. Secondly, the bonding strength with resin can be enhanced through browning treatment of ceramic copper-clad laminates. Patent number CN202310488289.5 discloses a browning scheme, which forms a rough, honeycomb-like organic copper oxide layer on the copper surface through chemical bonding with Cu2O. During lamination, this organic copper oxide film undergoes a curing and cross-linking reaction with the resin, providing better interfacial bonding.

[0004] Browning treatment is often used in the lamination process of multilayer boards. It cannot be directly soldered to chips, which affects the welding capability. An overly rough structure can easily form welding voids in the welding layer, affecting the reliability of IGBT modules. The browning film has strong acid resistance, which is difficult to remove effectively by acid washing, affecting the adhesion of the coating.

[0005] In summary, this invention provides a selective roughening method for ceramic copper-clad laminates, which can effectively solve the problems of wettability, voids, and solder diffusion in functional area chip soldering. Summary of the Invention

[0006] The purpose of this invention is to provide a selective roughening method for ceramic copper-clad laminates. In this method, the ceramic copper-clad laminate is roughened and pre-coated with nano-silicon and organosilane layers to enhance the anchoring effect. After roughening, it is protected by a mask. Chemical polishing is used to achieve local roughening and plating. Furthermore, a concave structure is achieved in the functional area, which effectively solves the problems of chip soldering wettability, voids, and solder diffusion in the functional area.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0008] A method for selective roughening of copper-clad ceramic laminates includes the following preparation steps:

[0009] S1 prints a layer of active solder between the ceramic and the copper foil;

[0010] S2 involves bonding a ceramic substrate with a solder layer printed on it to a copper foil at a sintering temperature of 800℃~1000℃ to form a ceramic copper-clad laminate.

[0011] S3 involves attaching or coating a resist layer onto the sintered ceramic copper-clad laminate, then exposing and developing the copper layer to protect the desired copper layer and exposing the unwanted copper layer to form an etched pattern. The copper is then etched in a CuCl2 system or FeCl3 etching solution.

[0012] S4 places the copper-etched ceramic copper-clad board into the solder layer etching solution to remove the unwanted solder layer.

[0013] S5 involves cleaning the patterned ceramic copper-clad board according to the following steps: roughening with a roughening solution, cleaning, acid washing, cleaning, impregnation with an impregnation solution, and drying, forming a surface pitted structure. In the impregnation step, the coating is completely penetrated into the pits and micropores of the rough surface by filling with nano-silicon and organosilane, which enhances the anchoring and improves the resin bonding force. The surface roughness Sa is greater than 0.2um and Sdr is greater than 0.15.

[0014] S6 will print a thermosetting wet film (5) on the roughened layer 4 of the roughened ceramic copper-clad board surface to form the structure shown in Figure C, exposing the area to be surface treated.

[0015] S7 places the ceramic copper-clad board obtained in S6 in a chemical polishing solution to polish and remove the surface roughness structure exposed by the mask treatment layer, reduce the surface roughness, and form a concave structure with a concave depth of 2-18um.

[0016] S8 finally processes the ceramic copper-clad board through nickel plating, chemical silver immersion, and then film removal to form the final structure, or after grinding, it covers the non-plated areas by secondary printing a mask through positioning holes, and then performs plating and film removal to finally form a composite form of bare copper and nickel and silver surface treatment.

[0017] As a further improvement to this scheme, the brazing layer in S1 is Ag, wherein the mass percentage of Ag is 70-80% or more, and the remainder is copper and Ti.

[0018] As a further improvement to this scheme, in S5, roughening is performed using a roughening solution, wherein the roughening solution is any one or more of organic acid, copper chloride, complex, and copper corrosion inhibitor.

[0019] As a further improvement to this scheme, the roughening solution contains formic acid 0.15-2.3 mol / L, copper ions 15-26 g / L, sodium diethyldithiocarbamate 0.12-0.35 g / L, 2-thiol imidazoline 0.03-0.11 g / L, and polyethyleneimine 0.45-1.1 g / L, and the roughening temperature is 23-30℃.

[0020] As a further improvement to this solution, in S5, impregnation is performed using an impregnation solution, which comprises the following components in volume parts.

[0021] 3-8 parts of 2-12nm nano-silicon solution;

[0022] KRN8026 organosilane 1-3 parts;

[0023] The rest is water.

[0024] As a further improvement to this solution, in S7, the chemical grinding solution contains:

[0025] The hydrogen peroxide content is 20V / V% to 70V / V%.

[0026] The alcohol content is 2.5V / V% to 5V / V%.

[0027] Corrosion inhibitor 0.1-0.3 g / L;

[0028] The content of organic amine complexes ranges from 1.2 V / V% to 4.5 V / V%.

[0029] As a further improvement to this scheme, in S7, the pH is 0.9 to 1.2, and the grinding rate is controlled at 0.6 to 1.1 μm / min.

[0030] The selective roughening method for ceramic copper-clad laminates of the present invention has the following advantages compared with the prior art:

[0031] 1. It achieves selective roughening and coating, forming a suitable roughness on the roughened surface to enhance the bonding force with the resin. At the same time, the surface does not have an organic film structure similar to browning, so the packaging plant does not need to open a window in the soldering area.

[0032] 2. By pre-coating the roughened area with nano-silicon solution and organosilane, the small size of nano-silicon and the good flow properties of organosilane are utilized to penetrate into the roughened concave structure, enhancing the anchoring effect; at the same time, hydrogen bonds, silicon-oxygen bonds and van der Waals interactions are formed with the copper surface to enhance the cohesive force.

[0033] 3. After chemical grinding of the functional area, the problem of welding voids caused by the roughened surface pitting is avoided, the surface weldability is good, and the concave structure of the welding area effectively prevents the solder from overflowing during the welding process and reduces the micropores of the silver plating layer.

[0034] Instruction manual illustrations

[0035] Figure 1 This is a schematic diagram of the etched structure of the present invention;

[0036] Figure 2 This is a schematic diagram of the structure after surface roughening treatment according to the present invention;

[0037] Figure 3This is a schematic diagram of the structure after masking treatment according to the present invention;

[0038] Figure 4 This is a schematic diagram of the structure after the functional area of ​​the present invention has been processed;

[0039] Figure 5 This is a schematic diagram of the structure after the coating treatment of the present invention;

[0040] Figure 6 This is a schematic diagram of the structure after processing using the selective roughening method for ceramic copper-clad laminates of the present invention;

[0041] Figure 7 This is a diagram showing the weldability test results of Embodiment 1 of the present invention;

[0042] Figure 8 This is a diagram showing the weldability test results of Comparative Example 1 of the present invention;

[0043] Figure 9 This is a diagram showing the surface structure analysis results before roughening in Example 1 of the present invention;

[0044] Figure 10 This is a diagram showing the surface structure analysis results after roughening in Example 1 of the present invention;

[0045] Figure 11 This is a diagram showing the surface structure analysis results after grinding in Example 1 of the present invention;

[0046] Explanation of reference numerals in the attached figures:

[0047] 1-Ceramic layer;

[0048] 2- represents the brazing layer;

[0049] 3- is copper foil;

[0050] 4- Surface roughening layer;

[0051] 5-Mask treatment layer;

[0052] 6-Functional Area Processing Layer;

[0053] 7-Coating;

[0054] 8-Low-roughness bare copper layer. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described below in conjunction with embodiments 1 to 8:

[0056] A method for selective roughening of copper-clad ceramic laminates includes the following preparation steps:

[0057] S1 prints a layer of active solder between the ceramic and the copper foil;

[0058] In S1, the brazing layer is Ag, with Ag accounting for 70-80% or more by mass, and the remainder being copper, Ti, and neodymium rare earth elements.

[0059] S2 involves bonding a ceramic substrate with a solder layer printed on it to a copper foil at a sintering temperature of 800℃~1000℃ to form a ceramic copper-clad laminate.

[0060] S3 involves attaching or coating a resist layer onto the sintered ceramic copper-clad laminate, then exposing and developing the copper layer to protect the desired copper layer and exposing the unwanted copper layer to form an etched pattern. The copper is then etched in a CuCl2 system or FeCl3 etching solution.

[0061] S4 places the copper-etched ceramic copper-clad board and solder layer in the etching solution to remove unwanted solder layer.

[0062] S5 The patterned ceramic copper-clad plate is cleaned, roughened with roughening solution, cleaned, acid-washed, cleaned, impregnated with impregnation solution, and dried to form a surface roughening layer 4 with a pitted structure on the surface.

[0063] In step S5, impregnation is performed using an impregnation solution, which comprises the following components in the indicated volume proportions.

[0064] 3-8 parts of 2-12nm nano-silicon solution;

[0065] KRN8026 organosilane 1-3 parts;

[0066] The rest is water.

[0067] In S5, roughening is performed using a roughening solution.

[0068] S6 will print a thermosetting wet film on the roughened surface layer 4 to form a mask treatment layer 5, such as Figure 3 As shown, the area to be surface treated is exposed;

[0069] After the S7 mask is applied, the ceramic copper-clad laminate is placed in a chemical polishing solution to remove surface roughening structures, reduce surface roughness, and form a concave structure, such as... Figure 4 The concave depth is 2-18 μm;

[0070] In S7, the chemical grinding solution contains:

[0071] The hydrogen peroxide content is 20V / V% to 70V / V%.

[0072] The alcohol content is 2.5V / V to 5V / V%.

[0073] The content of organic amine complexes ranges from 1.2V / V to 4.5V / V%.

[0074] Corrosion inhibitor 0.1-0.3 g / L.

[0075] In S7, the pH is 0.9–1.2, and the grinding rate is controlled at 0.6–1.1 μm / min.

[0076] S8 finally uses the ceramic copper-clad laminate obtained from S7, which is then nickel-plated and chemically silvered to form a... Figure 5 The structure is then subjected to defilming to form, such as Figure 6 structure.

[0077] The selective roughening method for the ceramic copper-clad laminate, wherein the roughening solution comprises formic acid 0.15-2.3 mol / L, copper ions 15-26 g / L, sodium diethyldithiocarbamate 0.12-0.35 g / L, 2-thiol imidazoline 0.03-0.11 g / L, polyethyleneimine 0.45-1.1 g / L, and a temperature of 23-30℃.

[0078] Example 1

[0079] 1. After patterning, the ceramic copper-clad substrate is cleaned, roughened, acid-washed, impregnated, and dried, wherein the cleaning concentration is 5% and the temperature is 45℃;

[0080] The preferred roughening solution contains 1.6 mol / L formic acid, 16 g / L copper ions, 0.12 g / L sodium diethyldithiocarbamate, 0.04 g / L 2-thiol imidazoline, and 0.5 g / L polyethyleneimine; the temperature is 23℃; the pickling concentration is 10% hydrochloric acid; the solution is impregnated with 3.5% and 1.5% KRN8026 organosilane coupling agent in a 3 nm silicone solution and then dried, resulting in a roughness Sdr of 0.71.

[0081] 2. Apply a dry film to the roughened surface layer 4, and form a mask treatment layer 5 through exposure and development, such as... Figure 3 As shown in the structure, the area to be surface treated is exposed;

[0082] 3. The developed ceramic copper-clad laminate is then subjected to a 5% acid pickling process; followed by treatment in a solution of 3% hydrogen peroxide, 6% sulfuric acid, and 3% 760 for 1 minute; and then further subjected to a chemical polishing solution containing 60% hydrogen peroxide, 3.5 g / L polyethylene glycol, 2.6 g / L thiourea, and 1.7% tetrahydroxypropyl ethylenediamine. The pH is adjusted to 1.2 using sulfuric acid, and the polishing rate is controlled at 0.8 μm / min to remove surface roughness, reduce surface roughness, and create a concave structure. Figure 4 The concave depth is 2-8 μm;

[0083] 4. Finally, the ceramic-clad copper board is directly surface-treated or... Figure 4Structurally, secondary printing masks are used to protect the copper layer area through positioning holes on the board surface. This covers part of the non-plated area, followed by chemical micro-etching and chemical silver deposition. The silver ion concentration is controlled at 0.8 g / L, and the temperature is set at 50℃ to form a plating layer of a certain thickness. Figure 5 The coating 7 in the middle has good adhesion and few micropores;

[0084] 5. Further stripping is performed at a concentration of 5% and a temperature of 50°C to form a film like... Figure 6 The structure achieves a local surface roughening layer 4, a low-roughness bare copper layer 8, and a plating layer 7; ensuring the solderability and bonding ability of the functional area, the roughened surface improves the bonding force with the molding resin, and the concave structure of the welding area effectively prevents the diffusion of solder.

[0085] The roughness test results of Example 1 are shown in Table 1.

[0086]

[0087] Comparative Example 1

[0088] The browning treatment described in existing technology CN202011329108.7 is adopted:

[0089] 8wt% concentrated sulfuric acid 120g / L, 30wt% hydrogen peroxide 20g / L, compound corrosion inhibitor 15g / L, KH550 20-50g / L, copper sulfate 70g / L, wetting agent 15g / L, polyethylene glycol monomethyl ether 8g / L, deionized water balance.

[0090] The weldability test results of Example 1 and Comparative Example 1 are shown in Table 2.

[0091]

[0092]

[0093] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent modifications made using the present invention are within the patent protection scope of the present invention.

Claims

1. A method for selective roughening of copper-clad ceramic plates, characterized in that, The preparation steps include the following: S1 prints a layer of active solder between the ceramic and the copper foil; S2 involves bonding a ceramic substrate with a solder layer printed on it to a copper foil at a sintering temperature of 800℃~1000℃ to form a ceramic copper-clad laminate. S3 involves attaching or coating a resist layer onto the sintered ceramic copper-clad laminate, then exposing and developing the copper layer to protect the desired copper layer and exposing the unwanted copper layer to form an etched pattern. The copper is then etched in a CuCl2 system or FeCl3 etching solution. S4 places the copper-etched ceramic copper-clad board into the solder layer etching solution to remove the unwanted solder layer. S5 involves cleaning the patterned ceramic copper-clad board according to the following steps: roughening with a roughening solution, cleaning, acid washing, cleaning, impregnation with an impregnation solution, and drying, forming a surface pitted structure. In the impregnation step, the coating is completely penetrated into the pits and micropores of the rough surface by filling with nano-silicon and organosilane, which enhances the anchoring and improves the resin bonding force. The surface roughness Sa is greater than 0.2um and Sdr is greater than 0.

15. S6 prints a mask treatment layer (5) on the roughened surface of the ceramic copper-clad laminate obtained in S5, exposing the area to be surface treated. S7 places the ceramic copper-clad board obtained in S6 in a chemical polishing solution to polish and remove the surface roughness structure exposed by the mask treatment layer, reduce the surface roughness, and form a concave structure with a concave depth of 2-18um. S8 processes the ceramic copper-clad laminate obtained in S7 through nickel plating, chemical silver immersion, and then film removal to form the final structure, or covers the unplated area of ​​the exposed surface of the ceramic copper-clad laminate obtained in S7 with a secondary printing mask through positioning holes. The unplated area is a low-roughness bare copper layer, which is then plated and removed to finally form a composite form of bare copper and nickel and silver surface treatment.

2. The selective roughening method for ceramic copper-clad laminates according to claim 1, characterized in that, The brazing layer in S1 is Ag, with Ag accounting for 70-80% or more by mass, and the remainder being copper, Ti, and neodymium rare earth elements.

3. The selective roughening method for copper-clad ceramic plates according to claim 1, characterized in that, In S5, roughening is performed using a roughening solution, which is any one or more of organic acids, copper chloride, complexes, and copper corrosion inhibitors.

4. The selective roughening method for ceramic copper-clad laminates according to claim 3, characterized in that, The roughening solution contains 0.15-2.3 mol / L formic acid, 15-26 g / L copper ions, 0.12-0.35 g / L sodium diethyldithiocarbamate, 0.03-0.11 g / L 2-thiol imidazoline, and 0.45-1.1 g / L polyethyleneimine, and the roughening temperature is 23-30℃.

5. The selective roughening method for copper-clad ceramic laminates according to claim 3, characterized in that, In step S5, impregnation is performed using an impregnation solution comprising the following components in parts by volume. 3-8 parts of 2-12nm nano-silicon solution; KRN8026 organosilane 1-3 parts; The rest is water.

6. The selective roughening method for ceramic copper-clad laminates according to claim 1, characterized in that, In S7, the chemical grinding solution contains: The hydrogen peroxide content is 20V / V% to 70V / V%. The alcohol content is 2.5V / V% to 5V / V%. Corrosion inhibitor 0.1-0.3 g / L; The content of organic amine complexes ranges from 1.2 V / V% to 4.5 V / V%.

7. The selective roughening method for ceramic copper-clad laminates according to claim 6, characterized in that, In S7, the pH of the grinding solution is 0.9 to 1.2, and the grinding rate is controlled to be 0.6 to 1.1 μm / min.

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