1. As mentioned above, electrolytic copper foil is usually electroplated or copper plated by wool foil. Suppose that the peak value of wool foil in the production process is abnormal, maybe the crystallization branching of coating is poor in the process of galvanizing / copper plating, and the peeling strength of copper foil itself is not good. When the bad foil is pressed into a thin sheet to form a printed circuit board, the copper wire will fall under the impact of external force when it pierces into the electronic factory. When the rough surface of the copper foil (i.e. the touching surface with the substrate) is peeled off, this bad copper extrusion will not cause significant side corrosion, but the peeling strength of the whole copper foil will be very poor.
2. The adaptability of copper foil to resin is poor: due to different resin systems, the curing agent used in some special functional laminates (such as HTG sheet) is generally PN resin. The molecular chain structure of the resin is simple and the crosslinking degree is low during curing. Therefore, it is inevitable to use copper foil with special peak value to match it. In the production of laminates, the copper foil used does not match the resin system, which leads to the lack of peel strength of the metal foil covered by the metal sheet, and the poor peeling of the copper wire when piercing.
2. Reasons for making printed circuit board laminate:
Under normal circumstances, only the hot pressing part of the laminate lasts for more than 30 minutes, and the copper foil and prepreg are basically completely bonded, so the adhesion between the copper foil and the substrate in the laminate will not be affected. However, in the process of laminating and stacking, assuming that polypropylene is contaminated or the surface of copper foil is damaged, the bonding force between the laminated copper foil and the substrate will be lack, resulting in positioning (only applicable to large plates) or scattered copper wire falling. However, the peel strength of copper foil is not abnormal in the off-line measurement.
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