I can remember the first ‘incident’ of black pad, years ago, when Epec started to use the electroless nickel immersion gold (ENIG) process. We didn’t notice the issue at the time, as it is not evident on the bare board, but received the complaint from assembly as it was later identified on completed assemblies.
IPC 4101 (Specification for Base Materials for Rigid and Multi-Layer Printed Circuit Boards) was released for publication in December, 1997. It was released as the replacement standard for MIL-S-13949. However, it contained a majority of the exact wording from the military standard. It maintained the “slash sheet” format appendix to the standard that specifies the resin and fiber system of different PCB laminates, along with testing parameters and properties. Initially there were 41 slash sheets, but as the industry opens up to “Lead Free” and “Green” processes, the slash sheets have increased to 66, the current revision.
Bow and twist of printed circuit boards (PCB) routinely rank among the highest levels of falsely identified non-conformance because it is perhaps the least understood. Envisioning a perfectly flat rigid circuit board as the standard is a fallacy believed by many incoming inspectors. Understanding the reasons and causes for PCB bow and twist can help resolve the issue at the board design stage.
There was a time when “Made in China” was synonymous with cheaper, poor quality products. "Buyer beware" was the common theme associated with outsourcing to any Asian PCB manufacturers. So how did Epec approach this challenge and succeed? It was by managing quality through intense auditing, training, and qualification. Epec understood at a very early stage that first-class quality products from Asian manufacturers would require consistent presence, training, and auditing.
Cleanliness of bare circuit boards increases in importance with advances in PCB technology that continue to decrease conductor spacing. Inorganic contamination within printed circuit board fabrication can lead to electrochemical migration. Electrochemical migration is the dissolution and movement of metal ions in presence of electric potential, which results in the growth of dendritic structures between anode and cathode. These dendritic growths, which were minimal over periods of time, were not a concern of "yesterdays" bare boards.
At Epec, we take workforce training very seriously. We readily invest in workforce education because it is a time-tested, proven path to improving manufacturing process development and customer satisfaction. In our experience, the educated worker is not only productive, they are adaptable problem solvers focused on satisfying our customers' most demanding needs.
When creating your optimal circuit board design, one factor that must be considered is the solder mask and whether to go with matte finish solder mask or gloss finish mask for your final product. Usually, most designers don't specify their preference and end up leaving the decision to the PCB fabricator. Most fabricators will likely default to a gloss finish, the more popular choice of the two.
This blog post addresses custom user interface testing in terms of functional test schemes that are completed prior to shipment. Generally, the first user interface assemblies shipment are for First Article acceptance testing where customers fully examine the first units for mechanical and electrical compliance to all engineering drawing and specifications.
When designing PCBs in a multi-up array, most designers choose v-score as the singulation method over traditional rout and breakaway tabs. The benefits of v-scoring pcb range from effortless removal of parts from panel form to realized cost savings with better utilization of panel area. When designing a circuit boards in array with v-scoring, there are two areas of concern - the angle of the cut, and the depth of the cut.
For rigid-flex printed circuit boards (PCBs), the space joining rigid material to flex material (Transition Zone) sometimes contains imperfections that, although acceptable, could impact effectiveness of the final part. Transition zone imperfections can include any of the following:
- Adhesive squeeze-out
- Protruding dielectric materials