Introduction to common causes of copper dumping on PCB circuit boards

by:A-TECH      2021-03-10
In the production process of PCB circuit boards, some process defects are often encountered, such as poorly falling off of the copper wires of the PCB circuit boards (also commonly referred to as dumping copper), which affects product quality. The common reasons for PCB circuit board rejection are as follows: 1. PCB circuit board process factors:   1. Copper foil is over-etched. Electrolytic copper foil used in the market is generally single-sided galvanized (commonly known as ashing foil) and single-sided Copper plating (commonly known as red foil), the common spoiled copper is generally galvanized copper foil above 70um. There is basically no mass spoiled copper in reddish foil and ashing foil below 18um.  2. A local collision occurred in the PCB process, and the copper wire was separated from the substrate due to external mechanical force. This poor performance is poor positioning or orientation, the copper wire will be obviously twisted, or scratches/impact marks in the same direction. Peel off the copper wire at the defective part and look at the rough surface of the copper foil, you can see that the color of the rough surface of the copper foil is normal, there will be no side erosion, and the peeling strength of the copper foil is normal.  3. The PCB circuit design is unreasonable. If a thick copper foil is used to design a circuit that is too thin, it will also cause the circuit to be over-etched and the copper will be thrown away. 2. Reasons for the laminate process:    Under normal circumstances, as long as the laminate is hot pressed for more than 30 minutes, the copper foil and the prepreg will be basically completely combined, so the pressing will generally not affect the copper foil and the substrate in the laminate. Binding force. However, in the process of stacking and stacking laminates, if the PP is contaminated or the matte surface of the copper foil is damaged, it will also cause insufficient bonding force between the copper foil and the substrate after lamination, resulting in positioning (only for large plates) Words) or sporadic copper wires fall off, but the peel strength of the copper foil near the off wires will not be abnormal. 3. Reasons for laminate raw materials:    1. Ordinary electrolytic copper foils are all products that have been galvanized or copper-plated on wool. If the peak value of the wool foil is abnormal during production, or when galvanizing/copper plating, the plating crystal branches are bad, causing copper The peel strength of the foil itself is not enough. After the bad foil is pressed into a PCB and plug-in in the electronics factory, the copper wire will fall off due to the impact of external force. This type of poor copper rejection will not cause obvious side corrosion after peeling the copper wire to see the rough surface of the copper foil (that is, the surface in contact with the substrate), but the peel strength of the entire copper foil will be very poor. 2. Poor adaptability of copper foil and resin: Some laminates with special properties, such as HTg sheets, are used now because of different resin systems. The curing agent used is generally PN resin, and the resin molecular chain structure is simple. The degree of cross-linking is low, and it is necessary to use copper foil with a special peak to match it. When producing laminates, the use of copper foil does not match the resin system, resulting in insufficient peeling strength of the sheet metal-clad metal foil, and poor copper wire shedding when inserting. From here, you can enter the pricing page https://www./
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