(1. 哈爾濱工業(yè)大學(xué) 現(xiàn)代焊接生產(chǎn)技術(shù)國家重點(diǎn)實(shí)驗(yàn)室，
哈爾濱 150001;
2. 哈爾濱理工大學(xué) 材料科學(xué)與工程學(xué)院, 哈爾濱 150080)
摘 要: 采用在波峰焊過程中常用的Sn-Bi-Ag-Cu無鉛釬料， 進(jìn)行了通孔波峰焊焊點(diǎn)剝離現(xiàn)象模擬實(shí)驗(yàn)。 剝離的斷面形貌和成分分析表明， 凝固延后及鉍元素偏析導(dǎo)致焊盤拐角附近的釬料區(qū)在結(jié)晶后期殘存液相， 并最終成為縮孔的聚集區(qū)， 結(jié)晶后期該區(qū)的低塑性使收縮應(yīng)變?nèi)菀壮^材料的塑性極限而發(fā)生開裂。 開裂機(jī)制與結(jié)晶裂紋機(jī)制相似。 強(qiáng)偏析元素鉍的存在導(dǎo)致剝離概率急劇提高， 鉍元素含量增加， 剝離的趨勢(shì)增加。 鉛污染也使剝離的概率顯著增加。 冷卻速度增加， 剝離趨勢(shì)減小。 大的冷卻速度能夠抑制偏析， 卻不能完全抑制剝離， 且會(huì)導(dǎo)致釬焊圓角表面裂紋增加。 避免鉛污染、 降低鉍的含量并控制冷卻速度可抑制剝離。
關(guān)鍵字: 無鉛波峰焊； 焊點(diǎn)剝離； 偏析； 結(jié)晶裂紋
（ 1. State Key Laboratory of Advanced Welding Production Technology, Harbin Institute of Technology,
Harbin 150001, China;
2. School of Materials Science and Engineering,
Harbin University of Science and Technology,
Harbin 150080, China）
Abstract: The lift-off phenomenon in through-hole wave soldering with Sn-Ag-Cu-Bi solder was investigated by the simulation experiment. It can be seen that the segregation of Bi becomes more remarkable at the corner of the solder body/PCB pad. The local irregularity of Bi delays the solidification of the solder at the above area and thus the residual liquid solder at that place becomes the aggregation area of shrinkage void during the following crystallization. The shrinkage strain exceeds the lowest plasticity of the Bi segregation solder in the later crystallization, and then crack comes into being from mechanism similar to that of the crystal crack. The presence of strong segregation element Bi exacerbates the probability of lift-off. The probability of fillet-lifting increases with increasing Bi content and the Pb contamination on the solidification behavior of through-hole solder joint, and decreases with the increasing cooling rate for solder joint. However, the fillet-lifting can not be completely eliminated by the rapid cooling for through-hole solder joint, and the rapid cooling can create cracks at the surface of solder. The fillet-lifting can be suppressed by eliminating Pb contamination, reducing the Bi content in solder and controlling the cooling rate for solder joint.
Key words: lead free wave soldering; lift-off; segregation; crystal crack
