英语翻译Thermal pad voiding control at QFN assembly is a major c

英语翻译
Thermal pad voiding control at QFN assembly is a major challenge due to the large coverage area,large number of via,and low standoff.Both design and process were studied for minimizing and controlling the voiding.Eliminating the via by plugging is most effective in reducing the voiding.For open via situations,a full thermal pad is desired for a low number of via.For a high number of via,a divided thermal pad is preferred due to better venting capability.Placement of via at the perimeter prevents voiding caused by via.A wider venting channel has a negligible effect on voiding and reduces joint continuity.For divided thermal pads,an SMD system is more favorable than a NSMD system,with the latter suffering more voiding due to a thinner solder joint and possibly board outgassing.Performance of a divided thermal pad is dictated by venting accessability not by the shape.Voiding reduction increases with increasing venting accessability,although the introduction of a channel area compromises the continuity of the solder joint.Reduced solder paste volume causes more voiding.Short and long hot profiles are most promising in reducing the voiding.Voiding behavior of QFN is similar to typical SMT voiding and increases with pad oxidation and further reflow.

热垫排尿控制在QFN大会是一个重大的挑战,由于覆盖面积大,大量的通过,以及低的对峙.其设计及工作过程,研究了降低和控制排尿.通过消除堵是最有效的降低了排尿.通过对开放的情况下,一个完整的热垫,是理想的低数量的通过.通过对大量的地位,导致一个分裂的热垫优先归功于良好的通风能力.通过在放置引起周边防止通过空洞.更广泛的排气通道排尿的影响可以忽略不计,减少关节的连续性.为划分热垫、一个SMD系统是一个NSMD优惠体系,后者由于遭受更多的空洞并可能板薄焊点内.一个分裂的热垫的性能取决于通风accessability不是由形状.增大,排尿减少排气accessability,虽然引入航道一带妥协焊点的连续性.锡膏量减少会引起更多的排尿.短期和长期的热曲线在降低空洞、最有前途的.QFN排尿行为类似于典型SMT排尿和随焊垫和进一步氧化.