IC封裝載板表面處理技術與無鉛錫球種類對焊接可靠度影響

Abstract

電子構裝中BGA (Ball Grid Array)載板會透過錫球經由焊接方式與PCB(Printed Circuit Board)進行連接，當產品摔落遭受外力撞擊後，容易在焊接面發生焊接點斷裂的問題。¬影響電子元件焊接強度主要是兩金屬經過焊接後所生成的介面合金共化物IMC(Inter-Metallic Compound)的強度，IMC的焊接強度又與基材的表面處理方式與錫球焊料成份有最直接的關係，因此如何挑選適當的表面處理方法並搭配合適的錫球焊料成份以達到最堅固的焊接強度，是攜帶式電子產品在面對經常性的摔落衝擊時最重要的考量因素。 本研究透過實驗設計進行此問題探討，目的在找出無鉛錫球種類與表面處理技術種類兩者最佳的焊接組合配方，達到期望最佳的焊接強度。本次實驗設計的因子為無鉛錫球種類及表面處理技術種類兩因子，其中無鉛錫球種類共採用四水準：SAC105(Sn98.5%-Ag1%-Cu0.5%)、SAC305(Sn96.5%-Ag3%-Cu0.5%)、SAC405(Sn95.5%-Ag4%-Cu0.5%)及Sn96.5-Ag3.5；表面處理技術種類共採用四水準： 浸鍍錫 IT(Immersion Tin)、電鍍鎳/電鍍鈀/浸金ENEPIG(Electroless Nickel Electroless Palladium Immersion Gold)、電鍍鎳/電鍍鈀ENEP (Electroless Nickel Electroless Palladium)及有機保焊劑OSP(Organic Solderability Preservatives)四種。由於希望這個最佳的組合在經過多次的迴焊過程中仍可保有最佳強度，故本研究將焊接次數設計成為一個區集劃分，而設計兩因子搭配一個完全隨機區集的實驗設計來進行研究。 本研究發現在無鉛錫球種類與表面處理技術種類中，以無鉛錫球SAC405搭配IT、ENEPIG或ENEP的表面處理技術可以在焊接過程後，獲得較佳的結合強度。

For electronic packaging, BGA (Ball Grid Array) substrate connects to PCB (Printed Circuits Board) by using solder ball welding process, solder joints may cause cracks while the electronic components get an accidental drop. The solder joints strength depends upon the strength of IMC (Inter-Metallic Compound) for two metal materials welding process. However, the welding strength of IMC is determined by surface finish process of basic materials and compositions of the solder ball materials. In this connection, it is very important to select a proper surface finish process of basic material and use proper solder ball to achieve the most welding strength. That will be the key consideration factors for those portable electronic products avoiding any negative impact by accidental drop by users. This study is done by DOE(Design and Analysis of Experiment) to try to find out the most proper weld compositions of the variety of Pb-free solder balls and surface finish technologies in order to achieve the best welding strength results. The factors of this DOE are Pb-free solder balls and the surface finish technologies; there are four levels for Pb-free solder balls, SAC105(Sn98.5%-Ag1%-Cu0.5%), SAC305(Sn96.5%-Ag3%-Cu0.5%), SAC405(Sn95.5%-Ag4%-Cu0.5%) and SN96.5-Ag3.5; and four levels for surface finish technologies; IT (Immersion Tin, ), ENEPIG (Electroless Nickel Electroless Palladium Immersion Gold), ENEP (Electroless Nickel Electroless Palladium) and OSP (Organic Solderability Preservatives) . The weld time is designed as an block which we may maintain the most welding strength during multi-reflow process. Therefore, it is defined to keep the experimental process by randomized complete block design for these two factors study. This experiment has demonstrated that Pb-free SAC405 collocates surface finish IT、ENEPIG or ENEP to own best welding strength after welding process of the variety of Pb-free solder balls and surface finish technologies.