Introduction:
The copper-free hole is a functional problem of PCB. With the development of science and technology, the precision (aspect ratio) of PCB becomes higher and higher, which not only brings trouble to PCB manufacturer (the contradiction between cost and quality) but also brings serious quality hidden trouble to downstream customers!
Classification and characteristics of copper-free holes
- Copper-free PTH hole: the electric layer of the surface copper plate is uniform and normal. The electric layer of the plate in the hole is evenly distributed from the orifice to the fracture.
- Copper-free for plate electric copper thin holes:
- There is no copper in the thin hole of the whole plate — both the surface copper and the porous copper plate are very thin. After micro etching before electric treatment, most of the plate electric copper in the middle of the hole is corroded. After electric etching, the plate electric copper is enclosed by the electric layer.
- The electric layer of the plate in the hole is uniform and normal. The electric layer of the plate in the hole is decreasing from the orifice to the fracture point, and the fracture point is generally located in the middle part of the hole. The uniformity and symmetry of the copper layer around the fracture point are good.
- Repair the broken holes:
- Copper inspection bad hole — table copper plate electric layer uniform and normal, hole copper plate electric layer has no taping trend, the fracture is irregular, may appear in the orifice may also appear in the middle of the hole, in the hole wall often appear rough convex and other bad, graph electricity after the fracture is covered by graph electric layer.
- Erosion maintenance of the reception-surface copper plate electric layer uniform and normal, hole copper plate electric layer has no tapering trend, the fracture is irregular, may appear in the orifice may appear in the middle of the hole, in the hole wall often appear rough convex and other bad, the fracture diagram electric layer does not cover the plate electric layer.
- No copper in the plughole: After the graph etching, there is obvious material stuck in the hole, most of the hole wall is corroded, and the graph electric layer at the fracture point does not cover the plate electric layer.
- No copper in the graph electric hole: the graph electric layer at the fracture point does not enclose the plate electric layer — the graph electric layer and the plate electric layer are uniformly thick, and the fracture point is uniformly broken; The graph electric layer shows a tendency of drawing until it disappears, and the plate electric layer continues to extend beyond the graph electric layer for a distance and then disconnects.
Improvement Direction:
- Operation (upper and lower boards, parameter setting, maintenance, exception handling);
- Equipment (crane, feeder, heating pen, vibration, air pumping, filtration cycle);
- Materials (plates, potions);
- Methods (parameters, procedures, processes, and quality control);
- Environment (variation caused by dirt, chaos, and clutter).
- Measurement (liquid medicine assay, copper visual inspection).
