Embedded PCB Design Tips
We all want to run our PCB fabrication process smoothly, at least with little trouble, so PCB design here is very critical. In this article, EPCB share our embedded PCB design experience for you to avoid some unnecessary mistakes.
Various solder defects and associated failures in embedded designs are not strange now due to smaller PCBs as well as shrinking ball size and pitch of ball-grid array (BGA), chip-scale, and quad-flat no-lead packaging.
For example, highly advanced BGA packages are required to be fitted with tiny balls ranging from 0.15 to 0.25 millimeter (mm) in size, and BGA ball pitch from a 0.8 to a 0.25 mm. Here pitch means the spacing between one BGA ball center and another ball center. It is obviously that there’s little area left for the soldering process, and that becomes one of the common solder defects during fabrication process.
To avoid embedded PCB defects, you should take the following points into consideration when designing. They are poor solder paste deposition and stencil quality, less perfect thermal profile, as well as inadequate assembly and inspection systems.
In addition, as PCBs are becoming much smaller and tend to be loaded with numbers of smaller device packaging like micro BGAs and chip-scale packaging, which can be hardly checked without machines, so to keep accurate solder deposition is a really serious challenge.
Remember too much solder paste placed on a BGA ball will cause defects, while less paste also will lead to a cold solder joint result. Bridging defects may be caused by overheated thermal profile. Solder-joint fatigue damage can cause micro hairline cracks on BGA ball. When deposited solder paste just wets the pad but doesn’t completely wet the ball, head-on-pillow defects can be caused.