This section describes the processes used to create the printed circuit design on the two outer layers of the panel.
1 RESIST APPLICATION OPERATIONS
The types of resist and application methods used by the PCB industry for Outer Layer Circuit Formation are the same as the Inner Layer Circuit Formation.
2 EXPOSURE UNITS
The resist that has been applied to the outer layers of a circuit board panel is selectively exposed to UV light using photo design tools and electric Exposure Units similar to those for inner layer circuit formation. However, the outer layer circuits are normally produced using a negative photoresist process. In a negative photoresist process, the resist covering the desired circuit traces remains soft because it is not exposed to the UV light, while the resist covering the undesired copper areas is exposed to the UV light and polymerized.
3 DEVELOPER
The unexposed resist is removed by a Developer to reveal the copper foil circuit pattern. this developer normally contains potassium carbonate to dissolve the soft unpolymerized resist.
4 ELECTROLYTIC COPPER PLATING LINES
Additional copper is added to the copper foil circuit pattern by electrolytic copper plating. The electrolytic copper plating line includes several cleaning or etching baths, rinses, and a copper sulfate plating bath.
5 TIN AND TIN/LEAD PLATING LINES
The new copper circuit design is protected from subsequent processing steps by adding a second layer of metal. Most PCB facilities use tin or tin/lead alloy for this step. The tin or tin/lead alloy is added to the plating line which may include cleaning baths, etching baths, rinses, and electrolytic plating baths.
6 RESIST STRIPPERS
Resist Strippers are used to dissolve and remove the polymerized resist to reveal the unwanted copper foil.
7 ETCHERS
unwanted copper foil is removed by ammoniacal etchers.
8 TIN AND TIN/LEAD STRIPPERS
The protective layer of tin (or tin/lead) is removed from the copper circuits using either a chemical stripping process or an electrolytic stripping process. Both processes normally use inorganic solutions. Occasionally this step is skipped per customer requirements, and the tin/lead plate is left on the panel for reflow.
Printed Circuit Board
1 RESIST APPLICATION OPERATIONS
The types of resist and application methods used by the PCB industry for Outer Layer Circuit Formation are the same as the Inner Layer Circuit Formation.
2 EXPOSURE UNITS
The resist that has been applied to the outer layers of a circuit board panel is selectively exposed to UV light using photo design tools and electric Exposure Units similar to those for inner layer circuit formation. However, the outer layer circuits are normally produced using a negative photoresist process. In a negative photoresist process, the resist covering the desired circuit traces remains soft because it is not exposed to the UV light, while the resist covering the undesired copper areas is exposed to the UV light and polymerized.
3 DEVELOPER
The unexposed resist is removed by a Developer to reveal the copper foil circuit pattern. this developer normally contains potassium carbonate to dissolve the soft unpolymerized resist.
4 ELECTROLYTIC COPPER PLATING LINES
Additional copper is added to the copper foil circuit pattern by electrolytic copper plating. The electrolytic copper plating line includes several cleaning or etching baths, rinses, and a copper sulfate plating bath.
5 TIN AND TIN/LEAD PLATING LINES
The new copper circuit design is protected from subsequent processing steps by adding a second layer of metal. Most PCB facilities use tin or tin/lead alloy for this step. The tin or tin/lead alloy is added to the plating line which may include cleaning baths, etching baths, rinses, and electrolytic plating baths.
6 RESIST STRIPPERS
Resist Strippers are used to dissolve and remove the polymerized resist to reveal the unwanted copper foil.
7 ETCHERS
unwanted copper foil is removed by ammoniacal etchers.
8 TIN AND TIN/LEAD STRIPPERS
The protective layer of tin (or tin/lead) is removed from the copper circuits using either a chemical stripping process or an electrolytic stripping process. Both processes normally use inorganic solutions. Occasionally this step is skipped per customer requirements, and the tin/lead plate is left on the panel for reflow.
Printed Circuit Board
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