Analysis Of The Cause Of No Copper In The Hole Of PCB Board

- Nov 17, 2018-

Pretreatment of the substrate

Some substrates may absorb moisture and some of the resins may not solidify well when they are pressed into the substrates, which may cause poor drilling quality due to the insufficient strength of the resins themselves when drilling holes, so necessary baking should be done when opening materials.In addition, some laminates may also have poor curing conditions of pp semi-cured sheet substrates, which will directly affect drilling and degumming slag activation of copper deposit. 

The drilling condition is very poor, mainly including: the resin dust inside the hole, rough hole wall, serious burr in the hole, burr inside the hole, copper foil nail in the inner layer, different lengths of tear section in the glass fiber area, etc., which will cause certain quality hazard to the chemical copper. 

In addition to mechanical treatment of surface contamination of the substrate and removal of burrs/flaps at the orifice, the brush plate clean the surface. In many cases, it also plays a role in cleaning out the dust in the orifice.In particular, more than a few non - stripping process treatment of double - panel 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 dust from the hole is a trend. 

The reasonable and appropriate technology of removing glue slag can greatly increase the hole ratio binding force and inner layer connection reliability, but the poor coordination between the process and the relevant tank liquid will also bring some incidental problems.If the slag is not enough, it will cause the micro hole in the hole wall, poor bonding of the inner layer, disconnection of the hole wall and blow hole.Excessive glue removal may also cause the glass fiber within the hole to protrude, rough in the hole, the glass fiber cutoff point, copper infiltration, and separation between the inner cuniform hole to break the inner copper, resulting in the fracture or discontinuity of the copper hole or the increase of the tension of the plating layer.In addition, the problem of coordinated control between several channels of glue removal is also very important. 

Insufficient swelling/swelling may result in insufficient gel removal slag;The swelling/swelling transition can remove the fluffy resin completely, so the casting will be activated when the copper is lost. Even if the copper is lost, defects such as resin subsidence and hole wall detachment may occur in the following process.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. 

The copper-free approach is no stranger to the industry, but how to control it?"Many colleagues have asked many times.After a lot of slicing, the problem still cannot be completely improved, and it is always repeated again and again. Today is produced by this procedure, and tomorrow is produced by that procedure.In fact, control is not difficult, but some people can not adhere to the supervision and prevention, always pain, foot pain. 

The following is my personal opinion and control method of no copper hole.The reason for the absence of copper in the hole is as follows:

1. Hole with dust or hole. 

2. When copper is sunk, the potion has air bubbles, but copper is not sunk in the hole. 

3. There is line ink inside the hole, no protective layer, no copper after etching. 

4. The acid and alkali solution in the hole after the copper deposit or after the plate electricity is not cleaned, and the parking time is too long, resulting in slow bite erosion. 

5. Improper operation, too long staying time during microerosion. 

6. If the pressure of the punching plate is too high, (the designed punching hole is too close to the conductive hole), it shall be disconnected in the middle. 

7. Poor penetration of electroplating solution (tin, nickel). 

For the reasons of the 7 major problems of no copper hole, improvement was made:

1. Add high pressure water washing and stripping process to the holes that are prone to dust (such as holes with a diameter of 0.3mm or less). 

2. Improve drug activity and shock effect. 

3. Change the screen version and the film.

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

Set a timer. 

Add blast holes.Reduce the force on the board. 

7. Conduct regular infiltration capacity test.