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Analysis of the Causes of No Copper in the Copper Plate of the PCB Board

Jul 20, 2018

Different resin systems and material substrates, different resin systems, also lead to significant differences in the activation effect and copper sinking during the copper treatment. In particular, some CEM composite substrates and high-frequency silver substrates are specific. When doing chemical copper-plating treatment, some special methods need to be taken. If it is normal copper, it is difficult to achieve good results.

 

Substrate pre-processing issues. Some substrates may absorb moisture and some of the resin may be poorly cured when pressed into a substrate, so that the quality of the drill may be poor due to insufficient strength of the resin itself during drilling, and the drilling of the material or the resin of the hole wall may be severely torn. Therefore, it is necessary to carry out the necessary baking when the material is opened. In addition, some laminates may also have poor curing conditions in the substrate of the pp prepreg, which will directly affect the drilling and degumming activated copper sinking. The drilling condition is too poor, mainly as follows: the resin dust in the hole is too large, the hole wall is rough, the air burr is serious, the burr in the hole, the inner copper foil nail head, the length of the tearing section of the glass fiber area, etc., will cause chemical copper A certain quality hazard.

 

In addition to the mechanical treatment to remove the surface contamination of the substrate and remove the burr/protrusion of the aperture, the brush is surface cleaned and, in many cases, also cleans and removes dust from the pores. In particular, it is more important to handle double panels without the desmear process. Another point to note is that you should not think that you can get rid of the glue and dust in the hole with the glue. In many cases, the effect of the slag removal process on the dust is very limited, because the dust will form a small glue in the bath. The group makes the bath liquid difficult to handle. The adsorption of the micelle on the wall of the hole may form a hole in the hole, and may also fall off the hole wall in the subsequent processing. This may also cause spot-like copper in the hole, so For multi-layer and double-panel, necessary mechanical brushing and high-pressure cleaning are also necessary, especially facing the development trend of the industry. Small orifice plates and high aspect ratio boards are becoming more and more common. Even ultrasonic cleaning sometimes removes dust from the holes.

 

Reasonable and proper removal of the slag process can greatly increase the hole ratio bonding force and the reliability of the inner layer connection, but the problem of poor coordination between the glue removing process and the relevant bath liquid brings some accidental problems. Insufficient slag, it will cause micro-holes in the hole wall, poor bonding of the inner layer, detachment of the hole wall, blown holes and other quality hazards; excessive glue removal may also cause the glass fiber in the hole to protrude, the hole inside is rough, the fiber fiber intercept point, copper infiltration The separation of the inner layer of the wedge-shaped hole and the blackening of the inner layer causes the copper to be broken or discontinuous or the stress of the coating of the coating layer is increased. In addition, it is also very important to coordinate the control problems between several tanks.

 

Insufficient bulkiness/swelling may result in insufficient desmear; when the bulking/swelling transition is more effective in removing the fluffy resin, it will also change the copper in the case of copper sinking, even if it sinks copper. In the post-process, defects such as resin sag and hole wall detachment may occur. For the de-sinking tank, the new tank and higher processing activity may also have some low degree of coupling. The single-function resin bifunctional resin and some tri-functional resin are excessively removed. The glue phenomenon causes the glass fiber of the hole wall to protrude, the glass fiber is difficult to activate and the bonding force with the chemical copper is worse than that between the resin. After the copper is deposited, the chemical copper stress is multiplied due to the deposition on the extremely uneven substrate. It can be clearly seen that the piece of chemical copper on the hole wall is detached from the hole wall after the sinking of copper, resulting in no copper in the subsequent hole.

 

There is no copper open circuit in the hole, which is no stranger to the PCB industry; how to control it? Many colleagues have asked many times. There are a lot of slicing, the problem still can't be completely improved, and it is always repeated. Today is the process, and tomorrow is the process. In fact, control is not difficult, but some people can't insist on supervising prevention. They always have headaches and pains.

 

The following are my personal views and control methods for the holeless copper open circuit. The reason for creating holes without copper is nothing more than:

 

1. Drilling dust plug holes or holes.

2. When the copper is frozen, there is a bubble in the syrup, and the hole is not covered with copper.

3. There is line ink in the hole, there is no protective layer on the electrode, and there is no copper in the hole after etching.

4. After the copper is immersed or the plate is charged, the acid and alkali syrup in the hole is not cleaned, and the parking time is too long, resulting in slow bite.

5. Improper operation, staying in the micro-etching process is too long.

6. The pressure of the punching plate is too large, and the design punch is too close to the conductive hole.

7. Electroplating solution (tin, nickel) has poor penetrability.

 

Improvements were made to the reasons why these seven large holes were free of copper.

 

1. Increase the high-pressure water washing and desmear process for holes that are prone to dust (such as 0.3mm pore size below 0.3mm).

2. Improve the activity and oscillating effect of the syrup.

3. Change the printing screen and the counterfeit film.

4. Extend the washing time and specify how many hours to complete the graphics transfer.

5. Set the timer. 6. Increase the explosion-proof hole. Reduce the force on the board.

7. Perform penetration testing regularly. So I know that there are so many reasons that the hole will have no copper open circuit, but also every time the slice is analyzed? ? Whether it is necessary to prevent prevention in advance.


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