芯片级尺寸封装返修技术工艺评定

与传统表面安装器件（SMD）方形扁平封装（QFP）相比，芯片规模封装（CSP）及焊球阵列封装（BGA）在元件尺寸方面显著缩减。回流后在芯片下方形成焊点的位置表明，目检是不可能的。对有缺陷的芯片而言，返修的唯一方法就是除去并替换该芯片。虽然元件拆除易于完成，但替换过程也许更复杂。比较两种PCB焊盘清洗方法并从最后的焊盘抛光得出结论，在第一个工艺技术中，采用热氮气脱焊技术回流焊盘上的任何残余焊料，并通过液化真空除去。第二个技术工艺涉及到使用网状焊料芯吸法及有刀片尖的焊接烙铁来除去PCB焊盘上的残余焊料。评定的四个淀积技术工艺，包括最小型模板、浸渍传递、接触及非接触模压技术。最小型模板用于把焊膏淀积到返修的元件部位的电子制造业的传统方法。

Rework Techniques Process Evaluation for Chip Scale Packages

The chip scale package (CSP) and ball grid array (BGA) have allowed significant reductions in component size compared to conventional surface mount devices (SMD) such as quad flat packs (QFP). However, the position of the solder joints formed (underneath the chip) after reflow means that visual inspection is impossible. For the defective chip, the only realistic method of rework is to remove and replace it. Component removal can be easily achieved, however replacement may be more complex.Two PCB pad- cleaning methods have been compared and conclusion drawn from the resultant pad finish. In the first technique, a hot nitrogen de-soldering gun was used to reflow any residual solder on the pad, which was then removed by a vacuum once liquefied. The second technique involved using braided solder wick and a soldering iron with a blade tip to remove residual solder from the PCB pad.Four deposition techniques have been assessed; these includes mini-stencil, dip transfer, on-and off-contact stamping. Mini-stencil is the traditional method used in the electronics manufacturing industry for the deposition of solder paste onto reworked component sites.