PCB defects come in many forms. The root cause can be in the supply chain, the assembly and soldering process, or in the board layout and component placing. Whatever the cause, these problems lead to extra cost, production delays or poor reliability in service.
The variety of potential causes means that a robust quality system must encompass every element of the process: from component sourcing, through design, process control and testing.
If we assume that the supply chain is set up and managed so that only genuine, certified, traceable and quality-assured components reach the production facility, where else should we look for potential PCB problems?
Component Selection and Placement
A thorough check against the engineering bill of materials is essential before starting any production runs, as is validation of component orientation and placement.
Other component placement issues are more design rather than manufacturing process-related. With greater miniaturisation comes more need to consider thermal management issues and the potential for problems with signal integrity.
Ensuring signal integrity is a complex design issue in modern compact PCBs. Keeping signal paths between connected components as short as possible is a cornerstone of good design. It’s also good practice to ensure that high frequency devices aren’t placed too close together or in parallel where they could cause interference.
Board layer stack-up also needs to be designed carefully to ensure, among other things, that there is always an unobstructed signal return path. Good board design will also ensure that sensitive components are kept clear of ‘noisy’ areas such as analog or power supply zones.
Design for Manufacturing
A thorough DfM process will avoid many of the potential PCB problems including acid traps, copper-to-edge clearance, thermal imbalances and ‘tombstoning.’
Details also matter in the manufacturing process, from the precise control of board heating and cooling, to the application of masks and the automated soldering process – whether wave or selective.
Inspection and Testing
PCB defects aren’t always visible. Dry or cracked solder joints, for example, might only show up when put through our automated high resolution X-ray inspection process.
Our AS 9100 certified design and production processes ensure that defect rates are minimal, while meticulous inspection and testing ensure that any issues are detected and rectified before assemblies leave our manufacturing facility.
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