Cause analysis of no copper in PCB board hole





The use of different resin system and material substrate, resin system is different, will lead to the activation effect of copper deposition and copper deposition significant differences.In particular, some CEM composite substrate plate and high frequency plate silver substrate specificity, when doing chemical copper processing, the need to take some special methods to deal with, if the normal chemical copper sometimes difficult to achieve good results. 



Substrate preprocessing problem

Some substrates may absorb moisture and itself in the pressure synthesis of substrates when part of the resin curing poor, so in the drilling may be due to the strength of the resin itself is not enough and the quality of the drilling hole is very poor, drilling dirt or hole wall resin tearing and digging serious, so the necessary drying is to open the material.In addition, some multi-layer lamination may also appear after the pp semi-curing sheet base material area branch curing poor state, will also directly affect the drilling and removal of slag activated copper, etc. 

The drilling condition is very bad, the main performance is: the resin dust inside the hole is much, the hole wall is coarse, the hollow burr is serious, the burr inside the hole, the copper foil nail head of the inner layer, the glass fiber area tear section length is not even, will cause certain quality hidden trouble to the chemical copper. 

In addition to the mechanical process of removing the surface contamination of the substrate and removing burrs/flaps from the orifice, the brush plate performs surface cleaning and, in many cases, also performs the cleaning and removal of dust from the orifice.In particular, a few more not through the process of removing rubber slag processing double face plate is more important. 

And one more thing to say, you don't think you in addition to the glue residue can out hole glue residue and dust, in fact, in many cases, in addition to the glue residue process of dust treatment effect is very limited, because in the dust to form micelles small bath, bath makes difficult to handle, the micelle adsorption tumor plating inside the hole wall hole can be formed, it is also possible in the subsequent fall off from the wall of hole machining process, it can also cause hole dotted no copper, so for multilayer and double panel, necessary mechanical brush plate and high pressure cleaning is also required, especially facing the industry development trend, small hole plate and high aspect ratio the board is more and more as a common condition.Even sometimes ultrasonic cleaning to remove the hole dust has become a trend. 

Reasonable and appropriate removal of slag technology, can greatly increase the pore ratio bonding force and the reliability of the inner connection, but the removal of glue technology and the related tank fluid coordination problems will also bring some accidental problems.In addition to the lack of plastic slag, will cause hole wall micro hole hole, poor inner combination, hole wall off, blowing hole and other quality hidden dangers;In addition to excessive adhesive, may also cause the hole glass fiber protrusion, hole roughness, glass fiber cut point, copper permeability, inner wedge hole broken inner black copper separation caused the hole copper fracture or discontinuity or coating fold coating stress increased.In addition, the coordination and control problem between several tank fluids is also very important. 

Insufficient swelling/swelling, which may lead to insufficient slag removal;Swelling/swelling transition and more can be removed in the already fluffy resin, then change out in the copper sinking will also activate the bad copper sinking is not on, even if the copper sinking may also appear after the process of resin sag, hole wall detachment and other defects;For in addition to the glue tank, a new slot and higher activity is likely to be some low coupling degree of monofunctional resin double resin and part three functions appear excessive degumming phenomenon, cause the hole wall of glass fiber, glass fiber is more difficult activation and chemical copper binding force between the resin and even worse, after heavy copper by the extremely uneven substrate deposition coating, chemical copper doubled and re-doubled will stress increase, serious can clearly see the copper after chemical copper pieces fall off from the hole wall of hole wall, causing subsequent hole without copper. 

Hole without copper open circuit, PCB industry is not unfamiliar, but how to control?Many colleagues have asked many times.I have made a lot of slices, but the problem still cannot be completely improved, so I always repeat it again and again. Today it is caused by this process, and tomorrow it is caused by that process.In fact, the control is not difficult, but some people can not go to adhere to the supervision and prevention of just, always head, feet. 


The following is a personal view of the hole without copper open circuit and control methods.The reason for producing holes without copper is nothing more than:

1. Drilling dust plug hole or thick hole. 

2. The liquid solution has bubbles when sinking copper, and the copper is not settled in the hole. 

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

4. The acid and alkali potions in the hole after copper sinking or after plate electricity are not cleaned, and the time of parking is too long, resulting in slow bite corrosion. 

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

6. The punching plate is under too much pressure, (the designed punching hole is too close to the conductive hole) the middle of the plate is disconnected neatly. 

7. Poor permeability of electroplating potions (tin, nickel). 

Aiming at the causes of the problem of no copper in the holes of the 7 major ones, improvement was made:

1. For dust-prone holes (for example, the pore diameter below 0.3mm contains 0.3mm), add high-pressure washing and slag removal process. 

2. Improve the activity and shock effect of the potion. 

3. Change the printing screen and counterpoint film.

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

Set a timer. 

6. Add explosion-proof holes.Reduce the force on the plate. 

7. Do regular permeability tests.


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