1. The copper foil is over-etched. The electrolytic copper foil commonly used in the market is generally single-sided galvanized (commonly known as ash foil) and single-sided copper plated (commonly known as red foil). Typically, galvanized foils are above 70 µm, while red and ash foils are below 18 µm, with almost no instances of batch copper rejection.
2. Local collisions during the PCB process can lead to separation of copper traces from the substrate due to external mechanical forces. This issue manifests as poor positioning or orientation, causing noticeable twisting of copper traces or scratches/impact marks in a consistent direction. Upon peeling off the affected copper trace and inspecting the rough surface of the copper foil underneath, the color and appearance should be normal, without signs of side erosion, and the peel strength of the copper foil should be within normal parameters.
3. The PCB circuit design may be flawed if thick copper foils are used for designing thin circuits, leading to over-etching of the circuit and unnecessary wastage of copper.
Reasons for the laminate process
Under normal circumstances, the copper foil and prepreg should be fully bonded when the high-temperature lamination process exceeds 30 minutes, ensuring that subsequent pressing does not compromise the bond strength between the copper foil and the substrate. However, during the stacking process, contamination of the prepreg (PP) or damage to the matte surface of the copper foil can lead to inadequate bonding strength after lamination. This may result in positional inaccuracies (especially noticeable in large panels) or sporadic detachment of copper traces. Despite these issues, the peel strength near the delaminated area typically remains within acceptable limits.
Reasons for laminate raw materials
1. Ordinary electrolytic copper foil undergoes galvanization or copper plating on wool foil. Abnormal peak values during wool foil production or poor crystal branching during galvanization/copper plating can lead to inadequate peel strength of the copper foil itself. When such defective foil is used in PCB manufacturing and assembly, external forces can cause copper traces to detach. While peeling reveals a rough copper foil surface (the contact surface with the substrate), overall peel strength across the foil is compromised.
2. Poor compatibility between copper foil and resin: Special laminates like HTg sheets use a different resin system, typically with a PN resin curing agent, characterized by a simple molecular chain structure and low cross-linking. Matching these with appropriate copper foil types is crucial. Mismatched copper foils in such laminates result in insufficient peel strength of the metal-clad laminate and increased risk of copper trace detachment during handling and assembly.
Additionally, potential causes of pad detachment during soldering on the client side include:
– Single and double panels are especially susceptible due to large ground areas, rapid heat dissipation, and the high temperatures required for soldering.
– Repeated soldering at a point can weaken the PCB pad.
– Excessive heat from the soldering iron can easily detach PCB pads.
– Applying too much pressure or prolonged soldering time with the soldering iron can also lead to PCB pad detachment.
2. Local collisions during the PCB process can lead to separation of copper traces from the substrate due to external mechanical forces. This issue manifests as poor positioning or orientation, causing noticeable twisting of copper traces or scratches/impact marks in a consistent direction. Upon peeling off the affected copper trace and inspecting the rough surface of the copper foil underneath, the color and appearance should be normal, without signs of side erosion, and the peel strength of the copper foil should be within normal parameters.
3. The PCB circuit design may be flawed if thick copper foils are used for designing thin circuits, leading to over-etching of the circuit and unnecessary wastage of copper.
Reasons for the laminate process
Under normal circumstances, the copper foil and prepreg should be fully bonded when the high-temperature lamination process exceeds 30 minutes, ensuring that subsequent pressing does not compromise the bond strength between the copper foil and the substrate. However, during the stacking process, contamination of the prepreg (PP) or damage to the matte surface of the copper foil can lead to inadequate bonding strength after lamination. This may result in positional inaccuracies (especially noticeable in large panels) or sporadic detachment of copper traces. Despite these issues, the peel strength near the delaminated area typically remains within acceptable limits.
Reasons for laminate raw materials
1. Ordinary electrolytic copper foil undergoes galvanization or copper plating on wool foil. Abnormal peak values during wool foil production or poor crystal branching during galvanization/copper plating can lead to inadequate peel strength of the copper foil itself. When such defective foil is used in PCB manufacturing and assembly, external forces can cause copper traces to detach. While peeling reveals a rough copper foil surface (the contact surface with the substrate), overall peel strength across the foil is compromised.
2. Poor compatibility between copper foil and resin: Special laminates like HTg sheets use a different resin system, typically with a PN resin curing agent, characterized by a simple molecular chain structure and low cross-linking. Matching these with appropriate copper foil types is crucial. Mismatched copper foils in such laminates result in insufficient peel strength of the metal-clad laminate and increased risk of copper trace detachment during handling and assembly.
Additionally, potential causes of pad detachment during soldering on the client side include:
– Single and double panels are especially susceptible due to large ground areas, rapid heat dissipation, and the high temperatures required for soldering.
– Repeated soldering at a point can weaken the PCB pad.
– Excessive heat from the soldering iron can easily detach PCB pads.
– Applying too much pressure or prolonged soldering time with the soldering iron can also lead to PCB pad detachment.
