鎳鈀金之厚度與磷含量對於印刷電路板表面焊墊處理之影響研究

在工業界中，化學鍍鎳浸金 (electroless nickel/immersion gold, ENIG) 是目前被廣泛使用的金屬表面處理，但由於 ENIG 焊墊表面處理浸金過程中會對鎳過度腐蝕，因而產生黑墊 (black pads) 的問題。近年來，化學鍍鎳鈀浸金 (electroless nickel/electroless palladium/immersion gold, ENEPIG) 逐漸取代 ENIG 被市場接受，ENEPIG 與 ENIG 相比，在鎳和金層之間鍍上一層鈀，鈀不只可以增加焊墊打線之穩定度，並且可以防止在浸金過程導致黑墊現象的產生。本研究所使用之 ENEPIG 焊墊是在固定鎳層厚度下 (200 μin) 利用兩種不同鈀層之系統 (純鈀與磷鈀) 在不同的厚度下 (2、4以及6 μin) 配合不同金層之厚度 (2與4 μin) 所組成，分別進行兩次回焊前後打線與無鉛焊接可靠度之比較，並利用掃描式電子顯微鏡 (SEM) 觀察焊墊之表面結構。實驗結果證明，ENEPIG在金層厚度為4 μin，鈀為4 μin 之磷鈀層，此焊墊具有穩定的打線接合能力與優異的無鉛可焊性。並由 SEM 觀察焊墊表面後，發現磷鈀具有較好的抗蝕能力。

關鍵字

鎳鈀金；打線；可焊性；表面處理

並列摘要

Nowadays, electroless nickel/immersion gold (Au/Ni(P), ENIG) metal finish is widely used in electronics industry. However, the immersion gold process causes corrosion on the nickel layer resulting in the so-called “black pads” defect. Recently, electroless nickel/electroless palladium/immersion gold (Au/Pd/Ni(P), ENEPIG) has gradually replaced ENIG because it can improve the stability of the wire bonding process and can limit Ni(P) corrosion. In this study, ENEPIG pads that consisted of 200-μin-thick Ni(P) layer, 2-, 4- and 6-μin-thick pure Pd or palladium phosphorous (PdP) layers, and 2- and 4-μin-thick Au layers were investigated. Two different processes (wire bonding and lead-free soldering) were also compared, while also looking into the effect of zero- or two-time reflow in both processes. Scanning electron microscopy (SEM) was used to examine the topography of the pad surface that resulted from these processes. As a result, the ENEPIG pad sample with 4-μin-thick Au layer and 4-μin -thick PdP layer was found to possess stable wire bonding capacity and excellent lead-free solder reliability. Furthermore, it was observed that the added PdP layer had imparted better corrosion resistance.

並列關鍵字

solderability ； metal finish ； wire bond ； ENEPIG

參考文獻

鄭永琦 (2008). 探討膨潤劑對環氧樹脂去膠渣行為之影響, 碩士論文, 化學工程學系, 中原大學.

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鎳鈀金之厚度與磷含量對於印刷電路板表面焊墊處理之影響研究

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