BONDING SUBSTRATE AND METHOD FOR PROTECTING SURFACES INTENDED FOR WIRE BONDING

Abstract

A bonding substrate is described having a contacting pad made of copper or a copper-based alloy for bonding wire, the contacting pad being covered with a corrosion inhibitor layer containing a nitrogen-containing aliphates as an active substance and a nitrogen-containing heterocyclic aromatics as a further active substance. The corrosion inhibitor layer, without any water content, contains 5% by weight or more of urea derivative or 3% by weight or more of triphenylguanidine or 2% by weight or more of tetrazole derivative or 5% by weight or more of 1-H-benzotriazole or 5% by weight or more of benzimidazole. In addition, an electronic module having such a bonding substrate and a method of protecting from corrosion surfaces made of copper or a copper-base alloy provided for wire bonding are disclosed.

Claims

1. A bonding substrate, comprising: a contacting pad made of copper or a copper-based alloy configured for bonding wire; a corrosion inhibitor layer covering the contacting pad, the corrosion inhibitor layer containing nitrogen-containing aliphates as an active substance and nitrogen-containing heterocyclic aromatics as a further active substance; wherein the corrosion inhibitor layer, without any water content, contains 5% by weight or more of urea derivative or 3% by weight or more of triphenylguanidine or 2% by weight or more of tetrazole derivative or 5% by weight or more of 1-H-benzotriazole or 5% by weight or more of benzimidazole.

2. The bonding substrate according to claim 1, wherein the corrosion inhibitor layer contains more aliphates than heterocyclic aromatics.

3. The bonding substrate according to claim 1, wherein the corrosion inhibitor layer, without any water content, contains at least 10% by weight of one or more of the following substances: urea derivates, aniline derivatives, triphenylguanidine, phenylurea, isothiocyanatobenzene and/or tetrazole derivatives.

4. The bonding substrate according to claim 1, wherein the corrosion inhibitor layer, without any water content, contains at least 10% by weight of tetrazole derivative.

5. The bonding substrate according to claim 1, wherein the tetrazole derivative is 1-phenyl-1H-tetrazole-5-thiol and/or sodium 1-phenyl-1H-tetrazole-5-thiolate.

6. The bonding substrate according to claim 1, wherein the corrosion inhibitor layer, without any water content, contains at least 8% by weight of 1-H-benzotriazole and/or benzimidazole.

7. The bonding substrate according to claim 1, wherein the pH of the corrosion inhibitor layer is less than 4.0.

8. The bonding substrate according to claim 7, wherein the corrosion inhibitor layer, without any water content, contains at least 1% by weight of phosphates.

9. The bonding substrate according to claim 1, wherein the corrosion inhibitor layer has a pH of 9 to 12.

10. The bonding substrate according to claim 1, wherein the corrosion inhibitor layer, without any water content, contains at least 10% by weight of one or more of the following substances: benzimidazoles, ethylene glycol isopropyl ether, aniline, isothiocyanatobenzene, 1-H-benzotriazole, bisphenol A ethoxylate.

11. The bonding substrate according to claim 1, wherein the corrosion inhibitor layer has a thickness of not more than 400 nm.

12. An electronics module, comprising a frame having compartments and bonding substrates according to claim 1 arranged in the compartments.

13. A method for protecting from corrosion surfaces made of copper or a copper-based alloy provided for wire bonding, the method comprising: covering the corrosion surfaces with an organic corrosion inhibitor layer containing a nitrogen-containing aliphate as an active substance and a nitrogen-containing heterocyclic aromatic as a further active substance, wherein the corrosion inhibitor layer, without any water content, contains 5% by weight or more of urea derivative or 3% by weight or more of triphenylguanidine or 2% by weight or more of tetrazole derivative or 5% by weight or more of 1-H-benzotriazole or 5% by weight or more of benzimidazole.

14. The method according to claim 13, wherein the corrosion inhibitor layer is applied as an aqueous solution.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above-mentioned aspects of exemplary embodiments will become more apparent and will be better understood by reference to the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0026] FIG. 1 shows a section of an electronic module having a frame with compartments in which bonding substrates are arranged with contacting pads.

DESCRIPTION

[0027] The embodiments described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of this disclosure.

[0028] FIG. 1 shows a section of an electronic module 1 which has a frame 2 having compartments 3. Bonding substrates 4 are arranged in some of the compartments 3, which bonding substrates can have an H-shaped cross-section. The bonding substrates 4 have contacting pads 4a, the bonding wires 5 of which are fastened, which lead to a printed circuit board 6.

[0029] The contacting pads 4a of the bonding substrate 4 are made of copper or a copper-based alloy, for example CuNi.sub.3SiMg, and are therefore susceptible to corrosion. The bonding substrates 4 or at least their contacting pads 4a are therefore covered with an organic corrosion inhibitor layer after their production.

[0030] The corrosion inhibitor layer is applied as an aqueous solution, for example, by dipping or spraying. After the application, the corrosion inhibitor layer can lose water and become a solid layer or remain a liquid layer.

[0031] For example, an acidic, aqueous solution of 1-H-benzotriazole and/or benzimidazole can be the corrosion inhibitor layer. The pH value of such a solution is preferably below 4.0, for example below 3.5, or even below 3.0. The solution preferably contains one or more inorganic acids, for example, phosphoric acid and/or sulfuric acid. In addition, such a corrosion inhibitor layer preferably contains phosphates, for example, 1% by weight or more. For example, 10 ml of 1-H-benzotriazole and/or 10 ml of benzimidazole are mixed with 1 liter of water and then applied to produce such a corrosion inhibitor layer. For example, 10 ml of inorganic acids such as phosphoric acid or sulfuric acid can be added to this mixture, wherein phosphates in addition to the acid can be dissolved, for example, 1 to 10 mg of ammonium molybdophosphate.

[0032] Such a corrosion inhibitor layer shows no negative effects on the bondability of a 300 m Cu wire to a CuNi.sub.3SiMg bonding substrate surface and on a leadframe surface punched therefrom.

[0033] For example, a corrosion inhibitor consisting of 1-phenyl-1H-tetrazole-5-thiol and/or sodium 1-phenyl-1H-tetrazole-5-thiolate in combination with urea derivatives and/or aniline derivatives and/or triphenylguanidine can also be used for the corrosion inhibitor layer, wherein such a corrosion inhibitor layer preferably additionally contains phenylurea and isothiocyanatobenzene. For this purpose, for example, 20 ml of such a corrosion inhibitor are mixed with 1 liter of water and then this aqueous solution is applied to a bonding substrate 4. The solution can dry on the bonding substrate and form a solid layer by crosslinking.

[0034] For example, a corrosion inhibitor can be used produced by mixing 10 mg of 1-phenyl-1-H-tetrazole-5-thiol, 10 mg of sodium 1-phenyl-1H-tetrazole-5-thiolate, 10 mg of one or more urea derivatives, 10 mg of one or more aniline derivatives, 10 mg of triphenylguanidine, 10 mg of phenylurea and 10 mg of isothiocyanatobenzene, wherein 1 liter of water is added to this mixture.

[0035] A further possibility consists in using benzimidazoles and ethylene glycol isopropyl ether as a corrosion inhibitor. Alternatively, aniline and/or isothiocyanatobenzene and/or 1-H-benzotriazole can each be used in combination with bisphenol A ethoxylate, wherein an acid can be added, for example, an organic acid such as acetic acid. 100 ml to 200 ml of this corrosion inhibitor can be mixed with 1 liter of water and then applied as an aqueous solution to a bonding substrate.

[0036] While exemplary embodiments have been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of this disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

LIST OF REFERENCE NUMBERS

[0037] 1 electronic module [0038] 2 frames [0039] 3 compartment [0040] 4 bonding substrate [0041] 4a contacting pad [0042] 5 wire [0043] 6 printed circuit board