Different resin systems and substrates will lead to significant differences in activation effect and copper deposition. Especially, some CEM composite substrates and high frequency silver substrates are specific. When chemical copper precipitation is done, some special methods should be adopted. If normal chemical copper precipitation is used, it is sometimes difficult to achieve good results.
Some substrates may absorb moisture and improper curing of some resins when pressing synthetic substrates. In this way, the quality of drilling holes may be poor due to insufficient strength of the resin itself, and there may be more drilling dirt or serious tearing of the resin on the wall of the holes. Therefore, it is necessary to bake the raw materials. In addition, some multi-layer laminates may also have poor solidification of branches in the base material area of PP semi-solidified sheets, which will directly affect drilling and deactivation of copper deposits.
The main performances of the drilling are: excessive resin dust in the hole, rough hole wall, serious hole burr, hole burr, inner copper foil nail head, uneven length of tear section in glass fiber area, etc., which will cause certain quality hidden danger to chemical copper.
In addition to mechanical treatment to remove the surface contamination of the substrate and remove the burrs/pipes at the orifice, the brush board cleans the surface. In many cases, it also cleans and removes the dust in the orifice. Especially, it is more important for the double panels which are not treated by the degumming slag process.
There is another point to explain, we do not think that the rubber residue and dust can go out of the hole with the rubber residue. In fact, in many cases, the dust removal process has very limited effect on the dust treatment, because the dust in the bath will form small micelles, which make the bath difficult to deal with. The micelle adsorbed on the hole wall may form an intra-hole plating tumour, and may also fall off from the hole wall in the subsequent processing. Therefore, mechanical brush and high pressure cleaning are also necessary for multi-layer and double panels, especially facing the development trend of the industry. Small orifice and high aspect ratio panels are becoming more and more common. Sometimes even the removal of dust in holes by ultrasonic cleaning has become a trend.
Reasonable and appropriate degumming slag process can greatly increase the hole ratio binding force and the reliability of inner connection, but the poor coordination between degumming process and related tank liquids will also bring some accidental problems. Insufficient debonding slag will cause quality problems such as micro-holes in the hole wall, poor internal bonding, separation of the hole wall, blow holes, etc. Excessive debonding may also result in prominent glass fiber in the hole, rough inside the hole, glass fiber cut-off point, copper infiltration, separation between broken inner wedge-shaped holes and black copper, resulting in fracture or discontinuity of the hole copper or increased stress of the coating fold coating. In addition, the problem of coordinated control among several tank fluids in addition to glue is also a very important reason.
Deficiency of swelling/swelling may result in inadequate debonding slag; transition of swelling/swelling may result in inadequate debonding slag; transition of swelling/swelling may remove all the fluffy resins, which will result in inadequate activation when copper is deposited; even if copper is deposited, defects such as resin subsidence and pore wall detachment may occur in the subsequent process; for debonding trough, new trough and higher treatment activity may also result in some single-function resins with lower bonding degree. Excessive de-gluing of energetic resins and some three-functional resins results in the prominence of glass fibers on the pore wall, the difficulty of activation of glass fibers and the worse bonding force with chemical copper than with resins. The stress of chemical copper will be doubled due to the deposition of coatings on extremely uneven substrates after depositing copper. It is obvious that one piece of chemical copper on the pore wall falls off from the pore wall after depositing copper, resulting in the subsequent pore inside. No copper is produced.
Kong Wutong is not unfamiliar to people in PCB industry, but how to control it? Many colleagues have asked many times. Slices have been made a lot, the problem can not be completely improved, always repeated, today is the process of production, tomorrow is the process of production. In fact, control is not difficult, but some people can not insist on supervision and prevention, always headache doctor, foot pain doctor foot.
Following is my personal opinion and control method on copper-free opening of holes. The reasons for copper-free pore formation are as follows:
1. Drilling dust plug hole or hole diameter.
2. When copper is deposited, there are bubbles in the liquid medicine, and copper is not deposited in the hole.
3. There is line ink in the hole, no electric protective layer and no copper in the etched hole.
4. After copper precipitation or plate electrolysis, the acid-base potion in the hole is not cleaned, and the stopping time is too long, resulting in slow biting.
5. improper operation and too long residence time in Micro-etching process.
6. The pressure of punching plate is too high (the design punching hole is too close to the conductive hole) and the middle of the punching plate is neatly disconnected.
7. The penetration ability of electroplating solution (tin and nickel) is poor.
In view of the causes of these seven problems, the improvement is made.
1. Adding high-pressure washing and deburring processes to dust-prone holes (e.g. holes less than 0.3 mm in diameter with 0.3 mm).
2. Enhance the activity and shock effect of the liquid medicine.
3. Printing screen and counterpart film.
4. Extend the washing time and specify how many hours to complete the graphic transfer.
5. Set a timer.
6. Increase explosion-proof holes. Reduce the force on the plate.
7. Perform permeability tests regularly.
Shenzhen Qunhui Electronics Co., Ltd. is a professional manufacturer of high-precision double-sided, multi-layer and impedance, blind buried holes, thick copper circuit boards. The products cover HDI, thick copper, backplane, rigid-flexible combination, buried resistance, golden finger and other circuit boards. It can meet the needs of customers for various products. Business cooperation: 13632635896.