銅/錫銀/銅結構在不同迴銲過程的熱遷移研究

本文主要觀察試片經過260℃迴銲測試之後，熱遷移對銲錫接點兩端界面上介金屬化合物的微結構的變化，很多熱遷移研究報告是發生在覆晶技術焊接點的電遷移測試，因為焦耳熱效應，溫度梯度橫跨於無電流的銲錫接點，在二端產生冷端和熱端，而有熱遷移的發生，以上的熱遷移是發生在固體狀態，在液態下的銲錫，擴散率是比固態快得多，而且銲錫的尺寸小，所得到的溫度梯度高得多，覆晶技術被運用在積體電路與基材之間的連接，近年來銲錫接點尺寸的縮小化，使得微小的溫度差就會在晶片與基材之間造成極大的溫度梯度，此溫度差異將驅動金屬原子往特定方向進行擴散，實驗準備了SnAg30um和SnAg15um的樣品，而此次實驗發現銲錫高度的縮減同時，在銲錫中也產生了不一樣的熱遷移現象，在三維積體電路封裝的技術中，金屬大多為Cu元素，在與微凸塊銲錫連結後，會形成Cu/SnAg/Cu 的接點結構，Cu原子在迴銲過程中，因為溫度梯度產生熱遷移，導致冷、熱二端IMC不對稱成長。而本實驗在定溫加熱板上進行迴銲測試的接點，頂部與空氣接觸，底部為熱端，頂部為冷端，其冷端Cu6Sn5 IMCs生成的速度異常的快速，而底部與定溫加熱板接觸的一端(熱端)，不管是在SnAg30um或者是SnAg15um樣品中都無明顯的變化，而樣品銲錫高度差異，為影響IMCs生成速度最直接的因素，而另外一差異為晶片端為熱端這一組實驗，其冷端Cu6Sn5 IMCs厚度增加的速度, 比基板端為熱端的實驗的增加速度快很多，推測原因為晶片端Silicon導熱快，PCB板導熱慢，導致晶片端為熱端這一組實驗兩端溫度差異大，而在銲錫內部形成較大的溫度梯度。

關鍵字

微凸塊銲錫；熱遷移現象；液態錫銀銲錫

並列摘要

This paper mainly observed sample after 260℃ reflow test, changes in interface microstructure of intermetallic compound of both sides of the solder joints in thermomigration, many study of thermomigration occur in electromigration test of solder joints of flip-chip technology, no current solder joints, temperature gradients build up across it’s due to the joule heating effect, with hot end and cold end between each side, the above thermomigration occurs in the solid state. Solder in the liquid state, diffusion rate is much faster than the solid state, and small size of solder, resulting much higher temperature gradient, Flip-chip bonding is use between the integrated circuit and the substrate connection, In recent years, reduction in size of solder joints, so that small temperature difference will cause great temperature gradient between the wafer and the substrate, this temperature difference driving metal atom diffusion to a specific direction, my experiment prepared sample SnAg15um and SnAg30um,and found the reduce height of solder while the solder had different phenomenon of thermomigration. In three-dimensional integrated circuit packaging technology, mostly metal is Cu elements, when Cu contact with micro solder bump will be form the joints structure Cu/SnAg/Cu, Cu atoms in the reflow process, because temperature gradient generate thermomigration, resulting the asymmetrical growth of IMCs in the solder joints between cold end and hot end.In this experiment, the solder joint reflowed on a hot plate, the top was exposed to the air. Therefore, the bottom was the hot end and the top was the cold end. IMC of Cu6Sn5 formed rapidly on cold end, but the hot end no change significantly whether in SnAg30um or SnAg15um samples,sample height difference is the most direct factor affecting IMCs growth rate.And another difference is the chip end is hot end of this set experiments, which IMCs of Cu6Sn5 thickness increase speed on cold end is much faster than the substrate end is hot end of this set experiments.

並列關鍵字

Microbumps ； Thermomigration ； Molten SnAg solder

參考文獻

[1] LIOU,JIAN-WEI, Application Trend and Fabrication Introduction of 3D Integrated Circuits Through Silicon Vias Technology, NANO COMMUNICATION,20_3(2013),20-27

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