| FU Yin-hui,LI Yuan-pu,DONG Dong.Effect of Sodium Sulfite Potassium Citrate Complexing Agent on Properties of Gold Plating Layer[J],52(4):390-398 |
| Effect of Sodium Sulfite Potassium Citrate Complexing Agent on Properties of Gold Plating Layer |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.04.035 |
| KeyWord:sodium nitrite-potassium citrate cyanide free gold plating bath complexing agent gold plating layer gold germanium eutectic welding |
| Author | Institution |
| FU Yin-hui |
Chengdu Siwei High-Tech Industrial Park Co., Ltd., Chengdu , China |
| LI Yuan-pu |
Chengdu Siwei High-Tech Industrial Park Co., Ltd., Chengdu , China |
| DONG Dong |
The 29th Research Institute of China Electronics Technology Group Corporation, Chengdu , China |
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| Abstract: |
| In order to study the influence mechanism of the complexing agent in the cyanide-free sodium nitrite-potassium citrate gold plating solution on the eutectic welding performance of Kovar substrate electrodeposited gold plating layer, so as to optimize the process range of the complexant content, improve the eutectic solderability of the gold plating layer, and expand the application of the sulfite-free gold plating process in the field of high-precision electronic equipment manufacturing, the effects of complexing agent in sodium nitrite-potassium citrate gold plating solution on the wettability of Au-Ge solder on the surface of gold plating layer, the adhesion of Au-Ge eutectic layer, surface and cross-sectional morphology, crystalline state, pores and micro morphology of Au-Ge eutectic welding interface were studied, by the methods of Scanning Electron Microscope and Energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD), and polarization curve, and the test of the porosity, wettability and shear strength of the gold-plated layer. The results show that the sodium sulfite and potassium citrate in gold plating solution can act as complexing agent. When the content of sodium sulfite and potassium citrate in the range of 120-160 g/L and 40-60 g/L, the surface of electrodeposited gold plating layer is weld abnormally and the micromorphology of electrodeposited gold plating layer surface and section presents cotton shape, loose, many pores, and the electrodeposited gold plating layer presents relatively large crystal size, and grows preferentially on (111) and (200) crystal face, and the electrodeposited gold plating layer cystal sizes are 95.5 nm and 66.4 nm respectively, and the interplanar spacing is 0.234 nm and 0.204 nm respectively. The content of complexing agent in gold plating solution has an obvious influence on the crystallization state and compactness of electrodeposited gold plating layer. The increase of complexing agent content can increase the cathodic overpotential of cyanide free gold plating solution, so as to make the prepared gold plating crystal more compact. The crystallization state and compactness of the electrodeposited gold plating layer is directly related to its gold germanium eutectic weldability. When the crystal size and crystal spacing of electrodeposited gold plating layer are smaller, and the compactness of electrodeposited gold plating layer is better, the surface eutectic welding quality of electrodeposited gold plating layer is better. When the content of sodium sulfite is 160-200 g/L and the content of potassium citrate is 60-100 g/L, the gold plating layer micromorphology of surface and section is obviously flat, dense, few pores and the gold plating layer presents relatively small grains, and grows preferentially on (311) crystal face, and the gold plating layer grain size is 43.7 nm, and the interplanar spacing is 0.123 nm, and the gold germanium solder on the surface of the gold plating layer is well wetted, the bonding force of the gold germanium eutectic layer is large, can reach more than 3 MPa, which meets the requirements of gold germanium eutectic welding. By reasonably controlling the content of sodium sulfite and potassium citrate in gold plating solution within a reasonable range, the crystallization state and compactness of electrodeposited gold plating layer can effectively controlled and the quality of eutectic welding on the surface of electrodeposited gold plating layer can be effectively improved. |
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