Technology of double sided printed wiring boards
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1. |
Copper clad laminate:  |
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- substrate thicknesses: 0.2, 0.25, 0.4, 0.5, 0.8, 1.0, 1.2, 1.55, 2.0, 2.5 mm
- copper layer thicknesses: 18, 35 µm
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2. |
Stacking, drilling, brushing:  |
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- range of hole diameter: 0.3–6.3 mm in 100 µm steps
- average positional offset: 50 µm
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3. |
Plating through-holes (making the hole walls conductive):  |
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- DOW chemicals
- CRIMSON direct electroplating
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Laminating photosensitive dry film:  |
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- DuPont Riston
- thickness: 38 µm
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5. |
Exposure and developing the resist:  |
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Electroplating copper:  |
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Electroplating tin – positive mask:  |
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8. |
Stripping the photoresist mask:  |
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9. |
Selective etching:  |
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- MacDermid (alkaline etchant solution)
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Double-sided printed wiring boards with plated through-holes, electroplated tin surface finish Recommended for hand soldering |
Double-sided printed wiring boards with plated through-holes, selective chemical surface finish Recommended for reflow and wave soldering |
10. |
Printing photosensitive solder mask and legend:  |
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Stripping tin:
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- colours: green, white, black, blue, red, yellow
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- MacDermid (acid stripper)
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Exposure by UV light, developing:
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11. |
Printing photosensitive solder mask and legend:  |
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- colours: green, white, black, blue, red, yellow
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12. |
Exposure by UV light, developing:  |
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13. |
Protecting solder pads:  |
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- selective, immersion silver finish
- thickness: 0.5 µm
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