诚然，球接工艺并不像倒装芯片组装、2.5D 和 3D 封装等其他工艺那样令人兴奋。以前，我会在新闻中读到包装技术的进步，以及在这个层面上出现的令人兴奋的创新，我就会想，"好吧，与之相比，球接工艺似乎太无趣了"。
While the ball-attach process can mistakenly be considered trivial, the soldering steps that go into this technique are indeed complex, and there are many variables which can affect the final ball-attached package. Luckily, if any readers encounter these common ball-attach assembly problems, Indium Corporation has the products to meet those challenges.
简要概括标准球接工艺，通常有两个步骤：预流步骤和实际 BGA 组装步骤。之所以需要预回流步骤，是因为在基板顶部进行封装组装的回流工艺（如倒装芯片封装）会导致基板底部焊盘的可焊性变差。换句话说，在 240°C 下回流倒装芯片封装，然后在 95°C 下清洗残留物，再在 130°C 下干燥封装，然后在 130°C 下涂抹模塑化合物，都会改变底部 BGA 焊盘的可焊性。这可能会令人沮丧，因为这些焊盘甚至还没有使用过！因此，需要采取预流化步骤来保护底部 BGA 焊盘的完整性。
那么，由此可能产生的常见缺陷有哪些呢？焊点可焊性差的主要后果是焊点剪切强度差，从而可能导致焊点失效。这在焊盘金属化很难焊接的情况下尤其明显，如铜 OSP。可焊性差还会导致焊点根本无法成型，造成非湿润开孔缺陷，最终导致电气开孔。
预流步骤导致的另一个常见故障是基片翘曲。用于半导体组装的基片通常很薄，在加热过程中容易发生翘曲。手机或汽车传感器中的一个翘曲元件就可能造成持久影响，因此应在预流产步骤中解决缺陷问题。
So, what does all this mean? While the ball-attach process is complex and has the potential to encounter many defects, Indium Corporation has solutions to solve these problems! Particularly noteworthy is our newest ball-attach flux, WS-823, a proven, one-step ball grid array ball-attach flux designed to eliminate the costly and warpage-inducing prefluxing step. WS-823 is a halogen-free, water-wash flux designed for a single-step ball-attach process that eliminates the prefluxing step in order to create reliable ball-to-pad joints. So, the common problems caused by prefluxing a substrate are not reduced, but altogether eliminated with this flux!
To learn more about Indium Corporation's BGA ball-attach fluxes, visit our website using this link.
