Cause Analysis and Solution of Copper Throwing Problem in PCB Factory
This article provides an overview of the common causes of copper peeling in PCB factories and offers a detailed analysis of these causes. Copper wire detachment, also known as copper peeling, is a common defect in PCB manufacturing. PCB factories often attribute this issue to problems with the laminate and demand compensation for the resulting losses.
Process Factors in PCB Manufacturing
1. Excessive etching of copper foil: The commonly used electrolytic copper foils in the market are generally single-sided galvanized (commonly known as gray foils) and single-sided copper-plated (commonly known as red foils). The phenomenon of copper peeling usually occurs on galvanized copper foils with a thickness of 70um or more, while red foils and galvanized foils with a thickness of 18um or less rarely exhibit batch copper peeling issues.
When the designed circuit is better than the etching line, any changes in the copper foil specifications without adjusting the etching parameters can result in excessive etching time in the etching solution. As zinc is an active metal, prolonged immersion of copper wires on LED display PCBs in the etching solution can lead to excessive etching on the sides of the circuit, causing the zinc layer backing certain fine circuits to completely react and separate from the substrate, resulting in copper wire detachment.
Another situation is poor rinsing and drying after etching, which leaves copper wires remaining in the etching solution for an extended period. This can also lead to excessive etching on the sides of the copper wires and copper peeling. This condition is often manifested by concentrated issues on fine circuits or similar defects appearing throughout the entire PCB under humid weather conditions. Peeling back the copper wires reveals a color change on the contact surface (known as the roughened surface), which is different from the normal color of copper foil, and the peeling strength of the thick wires is normal.
2. Collisions during the LED display PCB manufacturing process: When there is localized collision during the manufacturing process of LED display PCBs, the copper wires can separate from the substrate due to external mechanical forces. This defect is usually characterized by positioning or directional problems, and the detached copper wires exhibit obvious distortion or scratches/impact marks in the same direction. Peeling back the copper wires in the defective area reveals a rough surface, normal copper foil color on the surface without side etching defects, and normal peeling strength of the copper foil.
3. Unreasonable design of LED display PCB circuits: Using thick copper foils to design fine circuits can also lead to excessive etching and copper peeling.
Laminate Process Factors
Generally, as long as the laminate exceeds 30 minutes in the high-temperature lamination stage, the copper foil and semi-cured resin will be adequately bonded. Therefore, the lamination process usually does not affect the bonding strength between the copper foil and the substrate in the laminate. However, during the lamination stacking process, if there is PP contamination or damage to the copper foil surface, it can result in insufficient bonding between the copper foil and the substrate after lamination. This can cause occasional copper wire detachment (for large boards) or sporadic copper wire detachment. However, the peeling strength of the copper foil near the detached wire will not be abnormal.
Raw Material Factors in PCB Lamination
1. Copper foil quality issues: The electrolytic copper foils commonly used in LED display screens are usually galvanized or copper-plated rough foils. If there are abnormalities in the rough foils during the production process or if the crystal branches of the plating layer are defective, the peeling strength of the copper foil itself may be insufficient. When this defective foil is pressed into sheets and made into PCBs, the copper wires can detach upon external impact during component insertion. In this case, peeling back the copper wires will reveal no obvious side etching on the copper foil surface (i.e., the contact surface with the substrate), but the overall peeling strength of the copper foil will be poor.
2. Mismatch between copper foil and resin: Some special performance laminates, such as HTg materials, use different resin systems, typically PN resins, which have a simple molecular chain structure and lower cross-linking degree during curing. Therefore, special peak copper foils need to be used to match these resin systems. If the copper foil used in the production of laminates does not match the resin system, it can result in insufficient peeling strength of the metal foil on the laminate, leading to copper wire detachment during component insertion.
These are the detailed analyses of the common causes of copper peeling in PCB factories. We hope this information is helpful to you.
Watt Smith
Collaborator & Editor
Hello! My name is Watt Smith working on Chipdatas. I write and share relevant articles on electronic components category.
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