PCB News - Cause analysis of PCB hole without copper defect

I. Introduction

Hole-free copper is a functional problem of PCB board. With the development of technology, the requirements for PCB accuracy(aspect ratio) are getting higher and higher. It not only brings troubles to PCB manufacturers(contradiction between cost and quality), but also to downstream customers. A serious hidden quality hazard has been planted! Let’s do a simple analysis on this, hoping to give some enlightenment and help to related colleagues!

2. Classification and characteristics of copper-free holes

1. 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.

2. There is no copper in the copper thin hole of the board:

(1) There is no copper in the thin holes of the electrical copper of the whole board-the electrical layers of the surface copper and the hole copper plate are very thin. Figure electric layer encased;

(2) There is no copper in the thin hole of the electric copper plate in the hole-the electric layer of the surface copper plate is uniform and normal, and the electric layer of the inner plate of 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. Copper layer left

The right has good uniformity and symmetry, and the fracture is covered by the electrical layer after the electrical image.

3. Repair broken holes:

(1) Copper inspection and repair 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 often appear on the hole wall Rough bumps and other defects, the fracture is covered by the electrical layer after the electrical connection.

(2) Corrosion inspection and repair of the concealed hole-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 often appears on the hole wall Rough bumps and other defects, the electrical layer at the fracture does not cover the electrical layer of the board.

4. No copper in the plug hole: After electro-etching, there is obvious material stuck in the hole, most of the hole wall is etched away, and the electric layer at the fracture is not covered by the electric layer of the board.

5. 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 and the electrical layer are uniform in thickness, 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.

3. Improvement direction:

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

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

3. Materials (plates, potions);

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

5. Environment (variation caused by dirty, messy and messy).

6. Measurement (syrup test, copper inspection and visual inspection)