| 摘要: | 現今最常被使用的金屬表面處理技術為化鍍鎳(electroless Ni)，無論是在化鎳金製程(ENIG)或鎳鈀金製程(ENEPIG)皆會被大量使用，化鍍鎳具有很好的耐腐蝕性，常被用於電子產品中，銅線路上的保護層。雖然化鍍鎳製程技術已有相對成熟的發展，但在鎳層表面仍然會有難以解決的缺陷的產生，其中，防銲綠漆的溶出在化鍍鎳製程中對鍍出的化鍍鎳鍍層的品質造成了極大的影響。當防銲綠漆固化反應不完全時，在將基板浸泡至鍍液的過程中便會溶出，進而影響銲墊在進行表面處理製程時的成果，化鍍鎳鍍層在邊緣可能會有跳鍍發生，而使銲墊邊緣(接近防銲綠漆的位置)的銅面裸露。
本研究針對防銲綠漆中含硫分子對化鍍鎳鍍層抗腐蝕性質進行一系列探討：首先，為了確認鍍層中的含硫量是否會對化鍍鎳鍍層的抗腐蝕性質造成影響，開發出一套簡易的檢驗方式確認化鍍鎳鍍層中的微量硫含量，確認化鍍鎳鍍層中的微量硫含量對化鍍鎳鍍層抗腐蝕性質無明顯影響後。進一步討論防銲綠漆中含硫化合物對化鍍鎳鍍層的抗腐蝕性質的影響機制：透過GC-MS檢測出防銲綠漆所溶出的含硫化合物為4-(Methylsulfanyl)benzalde，將其添加至鍍液中完成化鍍鎳製程，根據CV以及OCV的結果表明，0到30 ppm 4-(Methylsulfanyl)benzalde在化鍍鎳反應的過程中會增強H2PO2-的氧化反應，使H2PO2-氧化成H2PO3-，並放出電子提供Ni2+的還原，同時，H2PO2-的氧化反應與H2PO2-還原成P的還原反應為結抗反應，因此Ni(P)層中的P含量也會隨之降低，透過XRD的分析結果也發現隨著P量的降低，Ni(P)層的結晶性也由非晶逐漸轉為多晶結構。然而，4-(Methylsulfanyl)benzalde的添加量超過30 ppm後，4-(Methylsulfanyl)benzalde會吸附在Cu金屬表面形成阻障層，阻止Ni2+還原反應的發生。將添加不同4-(Methylsulfanyl)benzalde濃度所鍍製出的Ni(P)試片進行電化學腐蝕分析，結果可以發現隨著4-(Methylsulfanyl)benzalde添加量的增加，Ni(P)層的抗腐蝕能力下降。由SEM結果得知，Ni(P)鍍層表面的crack寬度變寬且數量變多，其原因是因為4-(Methylsulfanyl)benzalde導致Ni(P)層中的P含量下降，結晶性由非晶變為多晶結構，使腐蝕溶液可經由晶界腐蝕攻擊Ni(P)，最終導致Ni(P)被嚴重腐蝕。
;The most commonly used surface finished treatment in recent years is electroless nickel, which is widely used in either the electroless nickel immersion gold process (ENIG) or the electroless nickel electroless palladium immersion gold process (ENEPIG). Electroless nickel often used in electronic products, as a protective layer on copper lines, owing to its good corrosion resistance. Although the electroless nickel plating process has been relatively matured, there are still difficult to prevent defects forming on the surface of the EN. The contamination of the plating solution may be the main cause of these surface defects, and the sources of the contamination may because of the solder mask dissolution. When the curing reaction of the solder mask is not complete, it will dissolve into plating solution during the ENIG process, which will affect the results of reliability of EN on the solder pad. Skip plating happened and exposed of the copper surface at the edge of the solder pad (close to the solder mask area) would be occurred.
A series of discussions on the corrosion resistance of EN affected by sulfur-containing molecules in solder mask would be presented in this study. First, in order to confirm whether the S content in the EN would affect the corrosion resistance, a simple test method is used to confirm the trace S content in the EN. Combined with the corrosion test result, it showed that the trace S content in the EN has no obvious effect on the corrosion resistance of the EN. The influence mechanism of sulfur-containing molecules in solder mask on the corrosion resistance of EN coating was further discussed. The sulfur-containing molecules dissolved in solder mask detected by GC-MS is 4-(Methylsulfanyl)benzalde. Thus, the EN process is completed with adding 4-(Methylsulfanyl)benzalde in the plating solution. According to the results of CV and OCV analysis, 0 to 30 ppm 4-(Methylsulfanyl)benzalde will enhance the oxidation reaction of H2PO2- during the EN process, so that H2PO2- is oxidized to H2PO3-, and release electrons to the reduce Ni2+ ions to Ni. At the same time, the oxidation reaction of H2PO2- would inhibit the reduction reaction of H2PO2-, thus, the P content in the Ni(P) layer will also decrease. The XRD analysis results also found that with the decrease of P content, the crystallinity of the Ni(P) layer gradually changed from amorphous to polycrystalline structure. However, when the addition amount of 4-(Methylsulfanyl)benzalde exceeds 30 ppm, 4-(Methylsulfanyl)benzalde will adsorb on the Cu surface to form a barrier layer, preventing the occurrence of Ni2+ reduction reaction. The Ni(P) specimens plated with different 4-(Methylsulfanyl)benzalde concentrations were subjected to electrochemical corrosion analysis. The results showed that with the increase of 4-(Methylsulfanyl)benzalde addition, the corrosion resistance of the Ni(P) layer decreased. From the results of SEM, it can be seen that the crack width on the surface of the Ni(P) coating becomes wider and the number of cracks increases. The reason is that the content of P in the Ni(P) layer decreases due to 4-(Methylsulfanyl)benzalde, and the crystallinity changes from amorphous to polycrystalline. The polycrystalline structure allows the etching solution to attack Ni(P) via grain boundary corrosion, which eventually causes Ni(P) to be severely corroded. |
