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引言 传统的共晶焊料filp chip组装,在芯片贴放前有两种施加助焊剂的方法:一种是施加在基板上,另一种是将芯片焊凸浸在一层助焊剂薄膜中。后一种方法提供更好的“连接力”(“Tack”),因此回流前芯片偏移的可能较小,另一方面,贴片前施加助焊剂可能有助于提高产能。这两种方法在回流焊接时都需要有氮气的环境。 如图1,回流后,必须用适合的填充胶对硅片进行底部填充,在毛细作用下填充胶会流进芯片底部。免清洗助焊剂的残留物既影响底部填充时的润湿及流动,又
Introduction Conventional eutectic solder filp chip assembly, in the chip placement before there are two ways to apply flux: one is applied to the substrate, and the other is the chip solder bump immersed in a layer of flux film. The latter approach provides a better “Tack”, so chip migration is less likely to occur prior to reflow, and on the other hand, applying flux prior to placement may help improve throughput. Both of these methods require a nitrogen atmosphere for reflow soldering. As shown in Figure 1, after the reflow, the silicon wafer must be filled with a suitable filling gel, and the filling gel will flow into the chip bottom under the capillary action. No-clean flux residue affects both the underfill wetting and flow, and