PCB Fabrication

Detailed explanation of PCB surface coating

by:A-TECH      2021-03-10
Many newbies who are just entering the industry often ask what is the surface coating of PCB? What problems should be paid attention to to ensure the reliability of the surface coating process? Next, the 'senior' editor of PCB proofing manufacturers will come to analyze some knowledge points about PCB coating with you, and hope to help you. The coating is used to protect the surface of the circuit copper foil. Copper is a good surface for soldering components, but it is easily oxidized; copper oxide hinders the wetting of solder. Although gold is now used to cover copper, because gold will not oxidize; gold and copper will quickly diffuse and penetrate each other. Any exposed copper will quickly form unsoldered copper oxide. One method is to use a 'barrier layer' of nickel, which prevents the transfer of gold and copper and provides a durable, conductive surface for component assembly. At present, in terms of PCB surface coating process, almost all manufacturers operate in accordance with the international standard IPC-A-610 acceptance standard for electronic components. Generally speaking, the IPC standard is that the surface coating is transparent and uniformly covering the circuit boards and components, and the coverage of the coating depends on the coating method. But be aware that most surface coatings now contain optical brighteners, which fluoresce when exposed to ultraviolet light. In turn, this makes it easier to inspect surface coatings. However, some defects of the coating will not be visible under ultraviolet light and may need to be inspected under white light. Due to the nature of the material, some coatings have weak UV fluorescence. This situation can be seen in many silicon surface coatings and may make inspections more difficult. For OSP coating, it is an organic soldering protection film on Cu surface that appeared in the 1990s. Certain cyclic nitrogen compounds, such as aqueous solutions containing benzotriazole (BTA), imidazole, alkyl imidazole, benzoimidazole, etc., can easily react with clean copper surfaces. The nitrogen heterocycles in these compounds form the surface of Cu Complex, this protective film prevents the Cu surface from being oxidized. In addition, I would like to add that non-electrolytic nickel and gold have only recently become a common final PCB surface coating, so industrial procedures may not be suitable. The above are some instructions on PCB surface coating. If you think it is useful, please hurry up and collect it. PCB independently developed a CRM online ordering website platform. The platform can realize a series of convenient functions such as pricing quotation, self-service ordering, uploading files, online payment, discounts, production progress inquiry, printing forms, after-sales consultation, etc. We will continue to invest in research and development Cost, the first to adopt advanced equipment and new technology, as always, with high-quality products and perfect services to give back to our customers. The company will continue to maintain its reputation, let the Chinese PCB proofing brand go to the world, and become a world-renowned PCB proofing service provider as soon as possible.
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