PCB News - What are the reasons why the copper wire of the impedance circuit board falls off?

The copper wire of the impedance circuit board is poorly dropped. The manufacturer always says that it is a problem with the laminate. In order to avoid the problem as much as possible, I have summarized some reasons for your reference.

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-plated (commonly known as red foil). Commonly thrown copper is generally galvanized copper above 70um. Foil, red foil and ash foil below 18um basically have no batch copper rejection.

2. There is another situation where there is no problem with the etching parameters of the impedance circuit board, but the copper wire is also surrounded by the residual etching liquid on the PCB surface after the etching, and the copper wire will also be produced if it is not processed for a long time. Excessive undercutting and dumping of copper. This situation is generally manifested as concentrated on thin lines, or during periods of wet weather, similar defects will appear on the entire PCB. Strip the copper wire to see that the color of the contact surface with the base layer (the so-called roughened surface) has changed. The color of the copper foil is different from the normal copper foil. The original copper color of the bottom layer is seen, and the peeling strength of the copper foil at the thick line is also normal.

3. The design of the circuit is unreasonable. Using thick copper foil to design a circuit that is too thin will also cause excessive etching of the circuit and dumping of copper.

4. As mentioned above, 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 during galvanizing/copper plating, the plating crystal branches are bad, causing the copper foil itself The peeling strength is not enough. After the bad foil pressed sheet material is made into a PCB, the copper wire will fall off when it is impacted by an external force when it is plugged in in the electronics factory. This kind of poor copper rejection will peel off the copper wire and look at the rough surface of the copper foil (that is, the surface in contact with the substrate). There will be no obvious side corrosion, but the peel strength of the entire copper foil will be very poor.

5. The problem of the potion, when there is no problem with the operation and the etching parameters, it may also be the reason for the poor etching of the potion, which leads to the unclean surface etching.

Therefore, if you want to completely avoid the cause of the copper wire falling off, when you choose a manufacturer, you must also avoid looking for a manufacturer with low process capability and poor sheet metal, otherwise it will be difficult to control the quality of the finished product.