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.
Within industries like electronics manufacturing, suppler self-surveys are very popular. At any given moment here at Epec, we are processing five or so supplier surveys. We send them out ourselves. I have dealt with supplier surveys, one way or another, for the last twenty something years. But, what purpose do they serve, and more importantly, what value do they provide to your organization?
We find that return merchandise authorizations (RMAs) are a powerful statement of a customer’s level of dissatisfaction. RMAs can offer evidence if a manufacturing process fell short of its goal, there was a lack of communication throughout processes, or even misdiagnosed a problem. In any case, we stand behind our product and are ready to support our customer.
In 1999 there were over 1,200 active printed circuit board (PCB) manufacturing facilities in the U.S. Today, there are fewer than 130. What has transpired at a lot of these manufacturing companies are small service businesses that act as a liaison between a manufacturer and their customers. In many instances, this is a valuable relationship; the products are low in technology and the risk is very minimal. However, why is it that we require ISO certification for our manufacturing locations but not for service providers?
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.
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 surface finish, the more popular choice of the two.
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: