PCB Tech - Analysis of bad vias in the circuit board factory

Analysis of bad vias in the circuit board factory

I. Introduction

Copper-free vias are also called vias. It is a functional problem of the circuit board. With the development of technology, the accuracy (aspect ratio) requirements of PCB circuit boards are also getting higher and higher. It not only brings troubles (cost and cost) to circuit board manufacturers. The contradiction of quality), and it has planted serious quality hidden dangers for downstream customers! Here is a simple analysis of this, and I hope that it can be enlightenment and help to relevant colleagues!

Second, the classification and characteristics of copper-free holes

1. There are burrs in the circuit board holes that cause the vias to be blocked. The hole wall is not smooth and burrs when drilling leads to copper sinking and uneven copper holes during electroplating. Once the customer debugs the thin copper area of the power-on hole, it may be burned, causing the PCB circuit board to open and cause the via to be blocked.

2, circuit board electric copper thin hole without copper:

(1) The whole board of the circuit board has no copper in the electrical copper thin holes: the electrical layers of the surface copper and the hole copper plates are very thin. After the electrical pre-processing, most of the electrical copper in the middle of the hole is etched away, and the electrical copper is etched after the electrical wiring. Figure electric layer encased;

(2) There is no copper in the thin hole of the electric copper in the hole: the electric layer of the surface copper plate is uniform and normal, and the electric layer of the hole in the hole shows a decreasing trend of sharpening from the hole to the fracture, and the fracture is generally in the middle of the hole, and the copper at the fracture Layer left

The right uniformity and symmetry are good, and the fracture is covered by the electrical layer after power-on.

3. No copper in PTH hole: The electrical layer of the copper plate on the surface is uniform and normal, and the electrical layer of the plate in the hole is distributed evenly from the hole to the fracture. After the electrical connection, the fracture is covered by the electrical layer.

Repair broken holes:

(1) Copper inspection and repairing broken holes: the electrical layer of the surface copper plate is uniform and normal, the electrical layer of the hole copper plate has no tendency to sharpen, and the fracture is irregular, which may appear in the hole or in the middle of the hole, and there will often be rough bumps on the hole wall. If the fault occurs, the fracture is covered by the electrical layer after the electrical connection.

(2) Corrosion inspection and repair: the electrical layer of the surface copper plate is uniform and normal, the electrical layer of the hole copper plate has no tendency to sharpen, and the fracture is irregular, which may appear in the hole or in the middle of the hole, and there will often be rough convexities on the hole wall. It is not good, and the electrical layer at the fracture is not covered by the electrical layer of the board.

4. No copper in the plug hole: After the electrical etching of the PCB circuit board, there are obvious substances stuck in the hole, most of the hole wall is eroded, and the electrical layer at the fracture is not covered by the electrical layer of the board.

5. Repair broken holes

(1) Copper inspection and repair of broken holes: the electrical layer of the copper plate on the PCB circuit board surface is uniform and normal, the electrical layer of the hole copper plate has no tendency to sharpen, and the fracture is irregular, which may appear in the hole or in the middle of the hole. Rough bumps and other defects appear, and the fracture is covered by the electrical layer after the electrical connection.

(2) Corrosion inspection and repair: the electrical layer of the copper plate on the PCB circuit board surface is uniform and normal, the electrical layer of the hole copper plate has no tendency to sharpen, and the fracture is irregular, which may appear in the hole or in the middle of the hole, and it is often Rough bumps and other defects appear, and the electrical layer at the fracture is not covered by the electrical layer of the board.

6. There is no copper in the electrical hole: the electrical layer at the fracture does not cover the electrical layer of the board-the electrical layer is uniform in thickness with the PCB electrical layer, and the fracture is uniform; the electrical layer tends to sharpen until it disappears, and the electrical layer of the board The layer exceeds the electrical layer and continues to extend for a certain distance before being disconnected.

Three, improvement direction

1, materials (plates, potions);

2, measurement (syrup test, copper inspection and visual inspection);

3. Environment (variation caused by dirty, messy and messy);

4. Methods (parameters, procedures, processes and quality control);

5. Operation (upper and lower board, parameter setting, maintenance, abnormal handling);

6. Equipment (crane, feeder, heating pen, vibration, pumping, filtration cycle).