錫鉛銲錫合金在電子構裝上的主要應用是在電子元件和印刷電路板的連接，但鉛對環境造成污染和人體健康的傷害已被許多國家所重視，無鉛銲錫合金之研發已成為目前最重要以及刻不容緩的重要課題。已研發的無鉛銲錫合金以錫鋅合金價格最低廉，但須藉由添加其它元素來改善其抗氧化性與潤濕性等性質。
本研究係探討本實驗室所開發的Sn8.5Zn0.5Ag0.01Al0.1Ga五元銲錫錫球實際應用在BGA (Ball Grid Array) 構裝上，當錫球受到電遷移（electromigration）與熱遷移（thermomigration）效應影響下所產生的變化。在本實驗每組測試試片中共觀察三個銲錫接點，先將試片研磨至觀察面，把試片放置烘箱內（120℃），再於其中兩個接點通以電流密度相同而方向相反的電流，實驗中施加電流密度共有6.11×103A/cm2，4.07×103A/cm2和3.06×103A/cm2三組，另一個銲錫接點則是不施加電流只進行熱處理做為通電實驗的對照組。
外加電流密度4.07×103A/cm2實驗試片通電114小時後，靠近基板處原本AuZn3與AgZn3所構成的三層介金屬化合物(Intermetallic Compound，IMC)，其原本附著在AuZn3的AgZn3已消失，此現象為IMC的分解，而在錫球中生成AgZn3。 電子在撞擊介金屬化合物時產生動量轉移，再加上焦耳效應產生的熱能，加速介金屬化合物分解，造成在電流集中（current crowding）的位置加速介金屬化合物明顯分解。
外加電流密度3.06×103A/cm2，AgZn3與AuZn3也會有分解的情形發生，伴隨著焦耳效應在銲錫球內部產生熱梯度，使分解後的金屬原子受熱遷移效應而移動，最終在銲錫球內部再生成介金屬化合物，而原本介金屬化合物的位置如果沒有被其它原子（Sn）填補，即會產生孔洞。基板端的三層介金屬化合物與基板有分離的情況，當在電遷移與熱遷移效應同方向作用下，極易造成介金屬化合物與基板間的Sn原子移動，並留下孔洞。
五元銲錫系統中，基板端的三層介金屬化合物經時效後，此三層介金屬化合物發生相變化而形成Zn-Ag-Au的化合物，此相變化亦會消耗銲錫內大量的針棒狀富鋅相，尤其以原本此三層介金屬化合物附近最為明顯。

Eutectic Sn-Pb solder are mainly used to connect the electronic devices and printed circuit board. But, many countries have concerned about lead, which would pollute environment and hurt human health. The development of lead-free solders has become the most important issue, oxidation resistance, wettability, and other properties.
This study investigated Sn8.5Zn0.5Ag0.01Al0.1Ga solder balls, which was developed by our lab. This study investigated the micro-structure of solder balls under electromigration and thermomigration effects. After assembly, we would apply different of current density to solder balls at 120℃.
Electrons would impact the intermetallic compounds (AuZn3 and AgZn3) seriously in current crowding section. The intermetallic compounds would decompose. The atoms coming from intermetallic compound decomposition would move in the direction of temperature gradient and react to form intermetallic compounds. Without other atom to occupy the site in which intermetallic compounds decomposed, it would be observed voids. If the directions of thermomigration and electromigration were the same, Sn atom would be affected seriously by temperature gradient and electric impaction, and move in the direction.
In this lead-free solder, the AgZn3-AuZn3-AgZn3 three layers compound would transfer and consume the Zn-rich phase in solder balls.

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