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Analysis of common reasons for copper rejection of PCB circuit boards in smt processing plants

Time:2022-08-26 Views:

Usually in the production process of the PCB circuit board, the pcb factory often encounters the situation that the copper wire of the PCB circuit board falls off seriously. What are the main reasons for copper rejection in circuit board technology?


  PCB circuit board process factors:


  1. The copper foil is over-etched. Electrolytic copper foils used in the market are generally divided into single-sided galvanized (commonly known as ashing foil) and single-sided copper-plated (commonly known as red foil). But the common copper removal rate is generally above 70um ashing foil, red foil and ashing foil below 18um basically do not have batch copper removal.


  2. In the smt technical workshop, a local collision occurred in the production process of the PCB board, and the copper wire was separated from the substrate due to external force. Scratches/bumps in the same direction.


  3. The PCB circuit design is unreasonable. Designing a circuit that is too thin with thick copper foil can also lead to over-etching of the PCB board and copper loss.


  Lamination process reasons:


  Under normal circumstances, as long as the laminate is hot pressed for more than 30 minutes in the high temperature section, the copper foil and the prepreg are basically completely combined, so the pressing generally does not affect the bonding force between the copper foil and the prepreg. The substrate in the laminate; but during the lamination process, if the PP is contaminated or the rough surface of the copper foil is damaged, it will also lead to insufficient bonding force between the copper foil and the substrate after lamination, resulting in positioning (only for large boards). ) or sporadic copper wires come off.


  Laminate raw material reasons:


  1. Ordinary electrolytic copper foil is a galvanized or copper-plated wool foil product. If the wool foil peaks abnormally during production or when galvanizing/copper plating, the coating dendrites are not good, causing the copper foil itself. Insufficient peel strength. After the inferior foil is pressed into a PCB circuit board, when the chip processing factory dips the plug-in, the copper wire will fall off under the impact of external force.


  2. Poor compatibility between copper foil and resin: The smt technical workshop of the pcb board manufacturer uses copper foil that does not match the resin system during production.


  Using the lamination of pcb circuit boards will lead to insufficient peel strength of pcb sheet metal-coated metal foil, and then there will be defective products such as copper wire falling off when using dip plug-ins.


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