回焊炉内氧气体积分数对焊接可靠性的影响

SMT(表面贴装技术)回焊炉工作时,炉中氧气体积分数的差异很大,从100×10–6至10000×10–6不等,在已验证氧气体积分数(O2)]超过4000×10–6会造成产品不良的前提下,针对500×10–6,1000×10–6,3000×10–6以及4000×10–6这四种不同的氧气体积分数,分别对回焊炉焊接的铜片上的锡焊点进行润湿角、EDS分析,对组装印制电路板(PCBA)上的锡焊点进行X射线、推力、通孔填充量等测试。结果显示,(O2)在4000×10–6以下,元件的焊接可靠性并无明显差异。选择(O2)=4000×10–6可降低回焊炉的氮气用量,节约成本。

Effect of different O_2 volume fractions on soldering reliability in reflow oven

There were great discrepancy of O_2 volume fractions in SMT reflow ovens in working,which was from 100×10~(-6) to 10 000×10~(-6).It was proved that the inferior product could be fabricated if O_2 volume fraction was over 4 000×10~(-6).The Sn solder points on copper foil soldered by the reflow oven were tested by contact angle experiments,EDS,and the PCBA solder points were tested by X-ray,push strength,the filling of plated-through-hole,etc.Experiments were carried out on the O_2 volume fractions of 500×10~(-6),1 000×10~(-6),3 000×10~(-6) and 4 000×10~(-6) in the reflow oven,respectively.The experiments data show that there is no obvious variation of the soldering reliability below 4 000×10~(-6) of O_2 volume fraction.So the N_2 stream in the reflow oven can be decreased to conserve the cost.