A method for improving the bonding strength of AMB partially silver-plated substrate packaging

Abstract

The present invention relates to the technical field of substrate packaging, and in particular to a method for improving the packaging bonding strength of a partially silver-plated AMB substrate. The present invention first removes oil and grease from the surface of the partially silver-plated substrate, then uses a browning agent to brown the substrate to form a browning film; finally, an acid wash liquid is used to thin the browning film, and then it is cleaned with an alkaline liquid. The scheme of the present invention improves the surface roughness of the copper, improves the packaging bonding strength, and has no significant effect on the silver layer.

Description

Technical Field

[0001] The invention relates to the technical field of substrate packaging, in particular to a method for improving the packaging bonding strength of an AMB partially silver-plated substrate. Background Art

[0002] In the electronics industry, packaged chips and some components need to be electrically connected to other circuits through lead frames. As integrated circuits become more and more complex, with more and more devices and functions, the wiring density of the circuits is getting higher and higher, and the shape and density (line spacing) of the lead frame are also required to be higher. Since the lines and shapes are small and complex, and the reliability of the circuit is very important, silver plating is usually used to improve the reliability of welding. However, due to the rapid migration of the silver plating, it is easy to cause circuit failure. Therefore, the application of local silver plating is becoming more and more widespread. The bonding strength of the package is related to the roughness of the substrate. Since silver is relatively stable and the roughness is not easy to improve, the existence of the silver-plated area limits the improvement of the bonding strength of the package to some extent.

[0003] In order to improve the packaging bonding strength of the module, a method is proposed to greatly optimize the packaging bonding strength of the copper surface from the perspective of changing the roughness morphology; and it has no obvious effect on other performances of the product. Summary of the invention

[0004] The object of the present invention is to provide a method for improving the packaging bonding strength of a partially silver-plated AMB substrate, so as to solve the problems raised in the above-mentioned background technology.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: a method for improving the packaging bonding strength of an AMB partially silver-plated substrate, comprising the following steps:

[0006] Step 1:

[0007] S11: mixing an additive, sulfuric acid and deionized water to obtain a degreasing agent; degreasing the surface of a substrate with the degreasing agent, and washing the degreased substrate twice with deionized water; the substrate is a partially silver-plated substrate consisting of a ceramic substrate, a copper layer covering both sides of the ceramic substrate and a silver-plated layer plated on the surface of the copper layer, and the silver plating method is a chemical silver process;

[0008] S12: degreasing the substrate with a degreasing agent, and washing the substrate twice with deionized water;

[0009] S13: Soak the substrate in a prepreg, and then use a browning agent to brown the surface of the substrate to form a browning film on the copper surface, and then use deionized water to wash it repeatedly for 3 times.

[0010] S14: air-drying and drying the partially silver-plated substrate washed in S13, and testing the surface roughness of the browning film;

[0011] Step 2:

[0012] S21: using a film stripping solution to thin the brown film on the surface of the substrate, and then using an acid solution to clean it;

[0013] S22: After the substrate is air-dried and baked, the roughness and wire hook force are checked.

[0014] Furthermore, in S11, the mass concentration of the solute in the degreasing agent is 15-25%, wherein the contents of the components, by weight percentage, are 10% additives, 5-15% sulfuric acid, and 75-85% deionized water.

[0015] Furthermore, in S12, the degreasing agent is a sodium hydroxide solution with a mass concentration of 5 to 20%.

[0016] Furthermore, in S13, the content of each component in the pre-soak is, by weight percentage, 3-7% of the imidazole compound, and the remainder is water.

[0017] Furthermore, in S13, the contents of the components in the browning agent are, by weight percentage, 2-5% hydrogen peroxide, 3-7% sulfuric acid, 15-25% browning agent, and the remainder is deionized water.

[0018] Furthermore, in S13, the browning agent is a mixture of an imidazole compound and sulfuric acid.

[0019] Furthermore, in S13, the surface roughness Sdr of the browning film is 1.0 to 2.0.

[0020] Furthermore, in S21, the stripping liquid is a sodium hydroxide solution with a mass concentration of 3 to 5%.

[0021] Furthermore, in S21, the acidic liquid is a sulfuric acid solution with a mass concentration of 2 to 6%.

[0022] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: the present invention provides a method for improving the packaging bonding strength of the AMB local silver-plated substrate, and the packaging bonding strength is improved by changing the roughness of the substrate surface. The selected local silver-plated substrate adopts the method of chemical silver precipitation to plate a silver layer on the surface of the copper layer, so there are two metals, silver and copper, at the same time. In order to ensure that the performance of both materials must be met, considering that silver has better chemical stability, it is considered to use browning solution to treat the copper surface so that the copper surface meets the roughness requirements of certain conditions. By controlling and adjusting the components and content in the browning solution, it is necessary to ensure that the browning solution has no great effect on the silver surface. Since silver reacts with sulfuric acid and hydrogen peroxide (the reaction equation is: 2Ag+H2O2+H2SO4=Ag2SO4+2H2O), the concentration of hydrogen peroxide cannot be too high, but the concentration of hydrogen peroxide directly affects the micro-etching rate, and the micro-etching rate affects the roughness, so the concentration of hydrogen peroxide cannot be too low. In the present invention, the mass concentration of hydrogen peroxide in the browning solution is controlled to be 2-5%, thereby ensuring that the silver surface is basically unchanged before and after the browning, and the roughness of the copper surface can also meet the product requirements, and the Sdr can reach 1.0-2.0, which greatly improves the packaging bonding force. Since the wire bonding hook force will be reduced by directly punching the browning film, the browning film is thinned. The browning film is neither acid-resistant nor alkali-resistant, and the hook force is significantly improved after thinning, and there is no obvious difference in the roughness value before and after thinning. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0024] Figure 1 The following are electron microscope images of the copper surface morphology before (a) and after (b) browning in Example 1 of the present invention;

[0025] Figure 2 is a graph showing the change in copper surface roughness before (c) and after (d) browning in Example 1 of the present invention;

[0026] Figure 3 This is a result diagram of the roughness of the browning film before thinning in Examples 1 to 5 of the present invention;

[0027] Figure 4 is a result diagram of the roughness of the browning film before and after thinning in Examples 1 to 5 of the present invention;

[0028] Figure 5 Result diagram of the wire hooking force before and after thinning of Examples 6 to 8 of the present invention;

[0029] Figure 6It is an electron microscope image of the silver layer on the surface of the browned substrate in Example 1(c), Example 2(d), Example 3(e), Example 4(f) and Example 5(g) of the present invention. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] In the present invention, the materials used and their sources are as follows: the additive is a potion stabilizer from Jiangsu Jingjiu Microelectronic Materials Co., Ltd., item number 619; the imidazole compound is benzoimidazole.

[0032] Embodiment 1: Browning a substrate comprises the following steps:

[0033] S11: by weight percentage, 10% additive, 15% sulfuric acid and 75% deionized water are mixed to obtain a degreasing agent with a solute concentration of 25% additive; the degreasing agent is used to degrease the surface of the substrate, and the degreased substrate is washed twice with deionized water; the substrate is a partially silver-plated substrate consisting of a ceramic substrate, a copper layer covering both sides of the ceramic substrate and a silver-plated layer plated on the surface of the copper layer, and the silver plating method is a chemical silver process;

[0034] S12: degreasing the substrate using a sodium hydroxide solution with a mass concentration of 20% as a degreasing agent, and washing the substrate twice with deionized water;

[0035] S13: Mix an imidazole compound and deionized water to obtain a pre-dip with a mass concentration of 7%; mix 5% hydrogen peroxide, 7% sulfuric acid, 25% browning agent (20% imidazole compound + 5% sulfuric acid) and 63% deionized water by weight to obtain a browning agent; immerse the substrate in the pre-dip, and then use the browning agent to brown the surface of the substrate to form a browning film surface roughness on the copper surface, and repeat washing with deionized water for 3 times;

[0036] S14: air-drying and drying the partially silver-plated substrate washed in S13 to obtain a brown substrate.

[0037] Embodiment 2: Browning a substrate, comprising the following steps:

[0038] S11: by weight percentage, 10% additive, 10% sulfuric acid and 80% deionized water are mixed to obtain a degreasing agent with a solute concentration of 20%; the degreasing agent is used to degrease the surface of the substrate, and the degreased substrate is washed twice with deionized water; the substrate is a partially silver-plated substrate consisting of a ceramic substrate, a copper layer covering both sides of the ceramic substrate and a silver-plated layer plated on the surface of the copper layer, and the silver plating method is a chemical silver process;

[0039] S12: using a sodium hydroxide solution with a mass concentration of 10% as a degreasing agent to degrease the substrate, and washing the substrate twice with deionized water;

[0040] S13: Mix an imidazole compound and deionized water to obtain a pre-dip with a mass concentration of 5%; mix 3% hydrogen peroxide, 5% sulfuric acid, 20% browning agent (15% imidazole compound + 5% sulfuric acid) and 72% deionized water by weight to obtain a browning agent; immerse the substrate in the pre-dip, and then use the browning agent to brown the surface of the substrate to form a browning film surface roughness on the copper surface, and repeat washing with deionized water for 3 times,

[0041] S14: air-drying and drying the partially silver-plated substrate washed in S13 to obtain a brown substrate.

[0042] Embodiment 3: Browning a substrate, comprising the following steps:

[0043] S11: by weight percentage, 10% additive, 5% sulfuric acid and 85% deionized water are mixed to obtain a degreasing agent with a solute concentration of 15%; the degreasing agent is used to degrease the surface of the substrate, and the degreased substrate is washed twice with deionized water; the substrate is a partially silver-plated substrate consisting of a ceramic substrate, a copper layer covering both sides of the ceramic substrate and a silver-plated layer plated on the surface of the copper layer, and the silver plating method is a chemical silver process;

[0044] S12: using a sodium hydroxide solution with a mass concentration of 5% as a degreasing agent to degrease the substrate, and washing the substrate twice with deionized water;

[0045] S13: Mix an imidazole compound and deionized water to obtain a pre-dip with a mass concentration of 4%; mix 2% hydrogen peroxide, 3% sulfuric acid, 15% browning agent (10% imidazole compound + 5% sulfuric acid) and 80% deionized water by weight to obtain a browning agent; immerse the substrate in the pre-dip, and then use the browning agent to brown the surface of the substrate to form a browning film surface roughness on the copper surface, and repeat washing with deionized water for 3 times,

[0046] S14: air-drying and drying the partially silver-plated substrate washed in S13 to obtain a brown substrate.

[0047] Embodiment 4: Browning a substrate comprises the following steps:

[0048] S11: by weight percentage, 10% additive, 8% sulfuric acid and 82% deionized water are mixed to obtain a degreasing agent with a solute concentration of 18%; the degreasing agent is used to degrease the surface of the substrate, and the degreased substrate is washed twice with deionized water; the substrate is a partially silver-plated substrate consisting of a ceramic substrate, a copper layer covering both sides of the ceramic substrate and a silver-plated layer plated on the surface of the copper layer, and the silver plating method is a chemical silver process;

[0049] S12: using a sodium hydroxide solution with a mass concentration of 10% as a degreasing agent to degrease the substrate, and washing the substrate twice with deionized water;

[0050] S13: Mix an imidazole compound and deionized water to obtain a pre-dip with a mass concentration of 7%; mix 2% hydrogen peroxide, 5% sulfuric acid, 25% browning agent (10% imidazole compound + 15% sulfuric acid) and 68% deionized water by weight to obtain a browning agent; immerse the substrate in the pre-dip, and then use the browning agent to brown the surface of the substrate to form a browning film surface roughness on the copper surface, and repeat washing with deionized water for 3 times,

[0051] S14: air-drying and drying the partially silver-plated substrate washed in S13 to obtain a brown substrate.

[0052] Embodiment 5: Browning a substrate, comprising the following steps:

[0053] S11: by weight percentage, 10% additive, 12% sulfuric acid and 78% deionized water are mixed to obtain a degreasing agent with a solute concentration of 22%; the degreasing agent is used to degrease the surface of the substrate, and the degreased substrate is washed twice with deionized water; the substrate is a partially silver-plated substrate consisting of a ceramic substrate, a copper layer covering both sides of the ceramic substrate and a silver-plated layer plated on the surface of the copper layer, and the silver plating method is a chemical silver process;

[0054] S12: using a sodium hydroxide solution with a mass concentration of 10% as a degreasing agent to degrease the substrate, and washing the substrate twice with deionized water;

[0055] S13: Mix an imidazole compound and deionized water to obtain a pre-dip with a mass concentration of 3%; mix 5% hydrogen peroxide, 5% sulfuric acid, 15% browning agent (10% imidazole compound + 5% sulfuric acid) and 75% deionized water by weight to obtain a browning agent; immerse the substrate in the pre-dip, and then use the browning agent to brown the surface of the substrate to form a browning film surface roughness on the copper surface, and repeat washing with deionized water for 3 times,

[0056] S14: air-drying and drying the partially silver-plated substrate washed in S13 to obtain a brown substrate.

[0057] Example 6: The brown film formed in Example 5 is thinned once, which is recorded as thinning 1;

[0058] S21: using a film stripping solution (a sodium hydroxide solution with a mass concentration of 3%) to thin the brown film on the surface of the substrate, and then cleaning it with an acid solution (a 2% sulfuric acid solution);

[0059] S22: The substrate is washed with water 7 times, air-dried, and baked, and the roughness and wire hook force are confirmed.

[0060] Example 7: The brown film thinned in Example 6 is thinned a second time, which is recorded as thinning 2;

[0061] S21: using a film stripping solution (4% sodium hydroxide solution by mass concentration) to thin the brown film on the surface of the substrate, and then cleaning it with an acid solution (3% sulfuric acid solution);

[0062] S22: The substrate is washed with water 7 times, air-dried, and baked, and the roughness and wire hook force are confirmed.

[0063] Example 8: The brown film formed in Example 7 is thinned three times; recorded as thinning 3;

[0064] S21: using a film stripping solution (5% mass concentration of sodium hydroxide solution) to thin the brown film on the surface of the substrate, and then cleaning it with an acid solution (6% sulfuric acid solution);

[0065] S22: The substrate is washed with water 7 times, air-dried, and baked, and the roughness and wire hook force are confirmed.

[0066] Experiment: The samples in Examples 1 to 8 were tested with reference to GJ / B548C-2021 Microelectronic Device Test Methods and Procedures.

[0067] Conclusion: The copper surface roughness Sdr in Examples 1 to 5 all reached 1.0 to 2.0; and there was no significant effect on the silver surface roughness; the surface roughness of the thinned brown-plated film in Examples 6 to 8 did not change significantly, and the wire hooking force of the brown-plated film after thinning was improved compared with the brown-plated film before thinning.

[0068] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0069] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for improving the bonding strength of AMB partially silver-plated substrate packaging, characterized in that: The following steps are involved: Step 1: S11: using a degreasing agent to degrease the surface of a partially silver-plated substrate, and washing the degreased substrate with deionized water; S12: degreasing the substrate with a degreasing agent, and washing the substrate with deionized water; S13: soaking the substrate in a prepreg, and then browning the surface of the substrate with a browning agent to form a browning film on the copper surface, and repeatedly washing with deionized water; wherein the content of each component in the browning agent, by weight percentage, is 2-5% hydrogen peroxide, 3-7% sulfuric acid, 15-25% browning agent, and the remainder is deionized water; the browning agent is a mixture of imidazole compounds and sulfuric acid; S14: air-drying and drying the partially silver-plated substrate washed in S13, and testing the surface roughness of the browning film; Step 2: S21: using a film stripping solution to thin the brown film on the surface of the substrate, and then cleaning it with an acidic solution; S22: After the substrate is air-dried and baked, the roughness and wire hook force are checked.

2. A method for improving the packaging bonding strength of an AMB partially silver-plated substrate according to claim 1, characterized in that: The partially silver-plated substrate consists of a ceramic substrate, a copper layer covering both sides of the ceramic substrate, and a silver layer formed on the surface of the copper layer by chemical silver deposition.

3. The method for improving the bonding strength of AMB partially silver-plated substrate packaging according to claim 1, characterized in that: In S11, the mass concentration of the solute in the degreasing agent is 15-25%, wherein the content of each component, by weight percentage, is 10% additive, 5-15% sulfuric acid, and 75-85% deionized water.

4. The method for improving the bonding strength of AMB partially silver-plated substrate packaging according to claim 1, characterized in that: In S12, the degreasing agent is a sodium hydroxide solution with a mass concentration of 5 to 20%.

5. The method for improving the bonding strength of AMB partially silver-plated substrate packaging according to claim 1, characterized in that: In S13, the content of each component in the pre-soak is, by weight percentage, 3-7% of the imidazole compound, and the balance is water.

6. The method for improving the bonding strength of AMB partially silver-plated substrate packaging according to claim 1, characterized in that: In S13, the surface roughness Sdr of the browning film is 1-2.

7. The method for improving the bonding strength of AMB partially silver-plated substrate packaging according to claim 1, characterized in that: In S21, the film stripping solution is a sodium hydroxide solution with a mass concentration of 3-5%.

8. The method for improving the packaging bonding strength of a partially silver-plated AMB substrate according to claim 1, characterized in that: In S21, the acidic liquid is a sulfuric acid solution with a mass concentration of 2 to 6%.

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