What is the “hair” of PCBs?(Hair of PCB)

Time for some trivia. PCBs also have hair like human beings. They are also covered by a villus-like layer just like human beings.

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Let the us tell you more.(Hair of PCB)

As an important part in multilayered PCB manufacturing, lamination is an extremely important aspect of PCB products. Black oxide treatment or brown oxidation preceding lamination is crucial procedure in the lamination process. As it is necessary to increase the coarseness of the copper foil surface on the inner layers to enhance the adhesiveness of the copper foil and resin before lamination, black oxide treatment or brown oxidation is the procedure used to enhance coarseness.

The color, black or brown, of treatment is the result of different chemicals, and the advantages and disadvantages of each chemical are as follows::   

  • After black oxide treatment, crystalline oxides in the form of long feathers are grown on the copper foil surface, looking like a villus layer.
  • Although long and thick black crystalline oxides have great coverage and an even color, they are less adhesive than brown crystalline oxides.
  • Brown oxidation grows gravel-like, nodular crystalline oxides characterized by uneven length.
  • Although gravel-like crystals have better adhesiveness than black oxides, a mottled surface is often found on the copper foil surface.
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Comparison of Black Oxidization and Brown Oxidization
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Figure 1. Black crystalline oxides
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Figure 2. Moisture absorption and PCB explosion: Oxidization marks
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Figure 3. Moisture absorption and PCB explosion: Chemical diffusion.

In conclusion, neither black oxidization nor brown oxidization is better than the other. Selecting the most suitable processes for different materials and product conditions to produce products with the most stable quality for customers is the core value of Cheer Time.

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