During the manufacturing process of PCB circuit boards, there are often some process defects, such as poor copper wire dropping (also known as copper throwing), which affects product quality. There are several common reasons for PCB circuit board copper throwing, including:

1、 PCB process elements:

1. Copper foil etching is excessive, and the electrolytic copper foil commonly used in the market is single-sided galvanized (commonly known as ashing foil) and single-sided copper plated (commonly known as reddened foil). The common copper foil used for copper throwing is generally galvanized copper foil with a thickness of 70um or more, while reddened foil and ashing foil with a thickness of 18um or less have never had batch copper throwing.

2. Local collisions occur in the PCB process, causing copper wires to detach from the substrate due to external mechanical forces. This defect manifests as poor positioning or directionality, with significant twisting or scratches/impact marks in the same direction when dropped copper wires. Peel off the defective copper wire and look at the surface of the copper foil. You can see that the color of the copper foil surface is normal, there is no side corrosion defect, and the peeling strength of the copper foil is normal.

3. Unreasonable PCB circuit planning, using thick copper foil to plan overly thin circuits, can also result in excessive etching of the circuit and copper stripping.

2、 Reasons for laminated board process:

Under normal circumstances, as long as the hot pressing section of the laminated board exceeds 30 minutes, the copper foil and the semi cured sheet are completely bonded, so the bonding generally does not affect the bonding force between the copper foil and the substrate in the laminated board. However, during the process of stacking and assembling laminated boards, if PP is contaminated or the surface of the copper foil is damaged, it can also lead to insufficient bonding between the copper foil and the substrate after lamination, resulting in positioning (only for large boards) or scattered copper wire falling off. However, there will be no abnormal peeling strength of the copper foil near the detachment line.

3、 Reasons for laminated board raw materials:

1. Ordinary electrolytic copper foil is a product that has been treated with zinc or copper plating on the raw foil. If the peak value of the raw foil is abnormal during production, or if the crystal branches of the coating are poor during galvanizing/copper plating, the peeling strength of the copper foil itself will not be sufficient. This poor foil restricts the copper wire from falling off under external impact when the PCB is made and inserted into the electronic factory. This type of copper throwing defect does not result in significant side corrosion on the surface of the copper foil (i.e. the contact surface with the substrate) when peeled off, but the overall peeling strength of the copper foil will be poor.

2. Copper foil and resin? Poor adaptability: Some special performance laminates currently in use, such as HTg sheets, use PN resin as the curing agent due to different resin systems. The molecular chain structure of the resin is simple, and the degree of cross-linking is low during curing, so special peak copper foil must be used to match it. When producing laminated boards, the use of copper foil does not match the resin system, resulting in poor peeling strength of the sheet metal foil and poor copper wire drop during insertion.

Article sourced from Jiangmen single and double-sided circuit boardhttp://www.yonghongpcb.com