Three Main Reasons for Copper Rejection in PCB Factories
1.1 The primary cause of copper rejection in PCB factories is often over-etched copper foil. Electrolytic copper foils used in the market are typically single-sided galvanized (commonly known as ashing foil) and single-sided copper-plated (commonly known as reddish foil). Copper rejection predominantly occurs with galvanized copper foils over 70um, while red foil and ashing foil below 18um usually do not experience batch copper rejection. If the copper foil specification is changed without adjusting the etching parameters, the copper foil may remain in the etching solution for an extended period, leading to excessive side etching of the circuit. This can result in the zinc layer of thin circuits being completely reacted and separated from the substrate, causing the copper wire to fall off. Inadequate washing and drying after etching can also contribute to copper rejection, as residual etching solution left on the PCB surface can surround the copper wire, particularly on thin lines or during humid weather. Examination of the stripped copper wire may reveal a roughened surface and a color different from normal copper foil, indicating inadequate bonding.
1.2 Another common cause of copper rejection is local collisions during the PCB manufacturing process, resulting in the separation of the copper wire from the substrate due to external mechanical force. This defect is characterized by poor positioning or orientation, twists in the dropped copper wire, or scratches and impact marks in a consistent direction. Inspection of the rough surface of the copper foil after peeling the flawed copper wire may reveal normal coloration and peeling strength.
1.3 Unreasonable PCB circuit design, such as thin circuits with thick copper foil, can also lead to excessive circuit etching and copper rejection.
In general, hot-pressing the laminate for over 30 minutes in the high-temperature section ensures complete bonding between the copper foil and the prepreg, minimizing the risk of copper rejection during pressing. However, contamination of the prepreg or damage to the rough surface of the copper foil during stacking may result in insufficient bonding force between the copper foil and the substrate after lamination, leading to sporadic copper wire detachment without impacting peeling strength near the off-wire.
3.1 Abnormal peak values or poor coating dendrites during the production of electrolytic copper foils may result in insufficient peel strength, leading to copper wire detachment under external force impact. This type of copper rejection does not typically cause significant side etching but can result in overall poor peeling strength of the copper foil.
3.2 Incompatibility between copper foil and resin, especially in laminates with special properties like HTg sheets, can result in poor peel strength of the metal-clad sheet metal foil and subsequent copper wire detachment when inserted. It is essential to match the copper foil with the resin system during production to ensure adequate bonding strength.
1.1 The primary cause of copper rejection in PCB factories is often over-etched copper foil. Electrolytic copper foils used in the market are typically single-sided galvanized (commonly known as ashing foil) and single-sided copper-plated (commonly known as reddish foil). Copper rejection predominantly occurs with galvanized copper foils over 70um, while red foil and ashing foil below 18um usually do not experience batch copper rejection. If the copper foil specification is changed without adjusting the etching parameters, the copper foil may remain in the etching solution for an extended period, leading to excessive side etching of the circuit. This can result in the zinc layer of thin circuits being completely reacted and separated from the substrate, causing the copper wire to fall off. Inadequate washing and drying after etching can also contribute to copper rejection, as residual etching solution left on the PCB surface can surround the copper wire, particularly on thin lines or during humid weather. Examination of the stripped copper wire may reveal a roughened surface and a color different from normal copper foil, indicating inadequate bonding.
1.2 Another common cause of copper rejection is local collisions during the PCB manufacturing process, resulting in the separation of the copper wire from the substrate due to external mechanical force. This defect is characterized by poor positioning or orientation, twists in the dropped copper wire, or scratches and impact marks in a consistent direction. Inspection of the rough surface of the copper foil after peeling the flawed copper wire may reveal normal coloration and peeling strength.
1.3 Unreasonable PCB circuit design, such as thin circuits with thick copper foil, can also lead to excessive circuit etching and copper rejection.
In general, hot-pressing the laminate for over 30 minutes in the high-temperature section ensures complete bonding between the copper foil and the prepreg, minimizing the risk of copper rejection during pressing. However, contamination of the prepreg or damage to the rough surface of the copper foil during stacking may result in insufficient bonding force between the copper foil and the substrate after lamination, leading to sporadic copper wire detachment without impacting peeling strength near the off-wire.
3.1 Abnormal peak values or poor coating dendrites during the production of electrolytic copper foils may result in insufficient peel strength, leading to copper wire detachment under external force impact. This type of copper rejection does not typically cause significant side etching but can result in overall poor peeling strength of the copper foil.
3.2 Incompatibility between copper foil and resin, especially in laminates with special properties like HTg sheets, can result in poor peel strength of the metal-clad sheet metal foil and subsequent copper wire detachment when inserted. It is essential to match the copper foil with the resin system during production to ensure adequate bonding strength.
