- 學位論文
無鉛錫球封裝體之掉落應力及溫度循環疲勞分析
Numerical Studies of Lead-free solder Subjected to Drop Stress and Thermal Cycling Tests
摘要
錫鉛合金(63Sn37Pb)是錫球材料及電子元件表面處理中，最廣泛採用的金屬材料之一，由於業界長久的使用，對錫鉛銲料的性質有著相當程度的了解，但因為含鉛物質的毒性會對人體造成傷害，因此各國家已有共識對於鉛元素的使用進行嚴格的限制，於是電子封裝產品正由錫鉛合金銲料漸漸地被無鉛合金銲料給取代。但因為無鉛銲料屬於脆硬性材料，容易在使用和搬運過程中受到碰撞或是不慎掉落而導致內部元件接點的損壞而導致產品的故障發生，或者是經歷周期性的熱循環時，內部各元件會因膨脹程度不同，在各元件間產生熱應變及熱應力，這些熱應變及熱應力之大小及分佈的情況會隨著熱循環的過程不斷的累積與變化，最後造成破壞。基於上述這些因素，故本研究將使用COMSOL有限元素分析軟體來模擬四種不同成份配比無鉛錫球(其成份為錫銀以及SAC305、355、405等錫銀銅合金)的三維晶圓級晶片封裝體(WLCSP)，分別做兩種不同的分析模擬。第一種為掉落模擬，觀察錫球受到衝擊作用時其應力分佈情況，再使用錫鉛合金錫球比較其抗衝擊的優劣性，期望能找出最適合取代含鉛材料的無鉛錫球；並針對 Yeh et al. [1]所提出衝擊應力會集中在封裝體錫球陣列的外圍部位，本研究將增加外圍錫球尺寸參數，觀察是否有效降低外圍錫球之應力。第二種為溫度循環負載模擬，觀察錫球於環境溫度循環負載下其熱與機械行為，再根據 Coffin-Manson 所提出之錫球疲勞壽命式，藉此計算錫球的疲勞壽命；最後針對李葉松[2]使用SAC405、105錫銀銅合金錫球之封裝體於溫度循環疲勞測試實驗以及數值模擬分析所提出的結果，如果產品處於溫度循環劇烈的環境下，選擇成份含銀量較高的錫球，會比含銀量低的錫球有更好的溫度循環疲勞性質，做驗證工作。 掉落衝擊分析結果顯示，四種不同成份配比之無鉛錫球中，成份為96.5Sn-3.5Ag與96.5Sn3Ag0.5Cu之錫球，在受到掉落衝擊後其抵抗衝擊效應的能力較為接近63Sn37Pb。而由三種不同成份配比之錫銀銅錫球來比較的話，可看出銀含量越低的話，則有越好的掉落衝擊特性；於改變周圍錫球尺寸參數分析結果顯示，增加其封裝體外圍錫球直徑，可有效降低錫球於掉落衝擊環境下應力分佈情形，大幅提升錫球之結構強度。 熱循環負載分析結果顯示，應變最大值皆發生於最外側的錫球上。而三種不同成份配比之錫銀銅錫球，其銀含量越高，有越好的溫度疲勞特性，趨勢與李葉松所提出結果相當一致。
並列摘要
Abstract in-lead alloy (63Sn37Pb) is a solder ball material and electronic components for surface treatment, one of the most widely used metal materials, due to the industry's long-term use, the nature of the tin-lead solder has a considerable degree of understanding, but because of lead substances toxic harm to human body, and therefore the countries have reached a consensus for the use of lead elements were strictly limited, so the electronic packaging products are made of tin-lead alloy solder is lead-free solder alloy gradually to replace. But because of lead-free solders are brittle hard materials susceptible to the use and handling process, or accidentally drop the collision caused damage to the internal components of contacts resulting in product failure occurs or is experiencing periodic thermal cycles, the internal each component will vary the degree of expansion, resulting in thermal strain between the elements and heat stress, strain and size of these hot thermal stress and division will continue with the process of accumulation of thermal cycles and change, and finally cause damage. Based on these factors, this study will use COMSOL finite element analysis software to simulate the composition ratio of four different lead-free solder balls (its ingredients, such as tin-silver and tin-silver-copper alloy SAC305,355,405) of three-dimensional wafer-level chip package (WLCSP), two different analyzes were done simulation. The first one is falling simulation, and then observed its role in the solder ball impact stress distribution, re-use tin-lead alloy solder balls compare the merits of its impact, hoping to identify the most suitable material to replace lead-free solder balls ; and for Yeh et al proposed will focus on the impact of stress in the peripheral parts of the package solder ball array, this research will increase the peripheral solder ball size parameters, to observe whether the peripheral solder ball effectively reduce stress. The second is the temperature cycling load simulation, observe solder balls under cyclic loading thermal and mechanical behavior at ambient temperature, according to the proposed Coffin-Manson fatigue life of the solder ball type, thereby calculate the fatigue life of solder balls; Finally, Lee pine use SAC405,105 tin-silver-copper alloy solder balls of the package body temperature cycle fatigue testing experiments and numerical simulation to analyze the results presented, if the product is in severe temperature cycling environment, select ingredients containing high silver content solder balls, will compared with low silver content solder balls have better temperature cycle fatigue properties, do validation. Drop impact analysis showed that the ability to lead-free solder ball four different ratios of ingredients, the ingredients and the 96.5Sn3Ag0.5Cu 96.5Sn-3.5Ag solder balls after being dropped its resistance to impact shock effect is closer 63Sn37Pb . The ratio consists of three different components of tin-silver-copper solder ball to compare, it can be seen that the lower silver content, then there are better drop impact properties; solder ball around to change size parameter analysis showed that increased its package body peripheral solder ball diameter, can effectively reduce the solder balls on the distribution of the impact of environmental stress drop, significantly increasing the structural strength of the solder ball. Thermal cycling load analysis showed that both the maximum strain occurred in the outermost solder ball. The ratio of the three different components of tin-silver-copper solder ball, its silver content is higher, there are better temperature fatigue characteristics, trends and Lee pine raised fairly consistent results.