Ten quality problems and solutions for PCB manufacturing

In the entire PCB manufacturing process, there are a lot of control points, there is a little bit of careless, the board will be broken, PCB quality problems are varied, due to the long production process, this is a headache, only one piece has a problem, then most of the components will also cannot use.
I have compiled a total of ten issues, listed here and attached some experience to deal with. Share with you.
1. Delamination (Layer separated)
Layer separated is the long-standing problem of PCB, occupy the top of the FAQ. The reasons for this may be as follows,
(1) Improper packaging or preservation, affected with damp
(2) Long time to save, more than the shelf life, PCB board is damp
(3) Supplier material or process problems
(4) Design materials problems or copper surface distribution is poor
Vacuum conductive bags or aluminum foil bags can be a good protection of water vapor intrusion. If there is a problem with the raw material or process of the product, the probability of being scrapped is quite large. Common possible causes include, black-oxide is bad, pp or inner layer is damp, pp gum volume is not enough, abnormal pressure etc.
In order to reduce this situation, special attention should be paid to the PCB supplier management of the corresponding process and the layered reliability test. For example the thermal stress testing, a good factory standard requires more than 5 times not to be layered, in the sample stage and the production of each cycle will be confirmed, and ordinary factory standards may be only 2 times, a few months to confirm once. The IR test can also be more to prevent the outflow of non-performing products, is an excellent PCB manufacturing factory must be.
Certainly, the design company's own PCB design will also bring hidden dangers of layering. For example, the choice of TG, for ordinary TG materials, temperature resistance will be relatively poor. In addition, the open large copper surface and too dense buried hole area is the hidden danger of PCB layering, need to avoid in the design.
2. Poor Solderability
Poor solderability is also one of the more serious problems, it may be caused by surface pollution, oxidation, nickel thickness anomaly, moisture absorption, soldermask on pad. Pollution and moisture absorption problems are easy solved, other problems are more troublesome, and there is no way through the test found that, this time need to pay attention to the PCB factory process capability and quality control plan, need to know PCB supplier's standards for overhaul, inspectors and overhaul staff whether have a good system of examination and induction.
3. Board Warping 
Main reasons caused board warping may be, material selection Problem, abnormal production process, poor control, improper transportation or storage, broken hole design is not strong enough, the copper area of different layers are too large. For some thin board, it can be required to compress the wood board before packing.
4. Scratch& Copper exposed
Scratches, copper exposed may bring quality risk, can most test the PCB factory management system and executive power. Many PCB companies will say that this problem is difficult to improve. But as long as PCB companies who are serious to promote the project, there are significant improvements.
5. Bad Impedance
PCB impedance is an important indicator refer to impedance performance, the general common problem is the impedance difference is relatively large between different batches. You can require supplier provide the test report for reference, and provide the comparison data of the side line diameter and the inner line diameter of the board.
6. BGA Solder Hollow

BGA solder hollow may cause main chip function is bad, and may not discover in the test, the hidden risk is very high. So now a lot of factories will use X-ray for inspection. The reason for this kind of bad possibility is the PCB hole residual liquid or impurities, vaporized after high temperature, or the laser hole on BGA solder pad type is bad. So now many HDI boards require electroplating over for vias to avoid this problem.
7. Soldermask foaming/shedding
This kind of problem is usually the PCB soldermask printing process control is abnormal, or the soldermask ink is not suitable (cheap, non-gold-type ink, not suitable for mounting flux), it may be SMT temperature is too high. To prevent batch problems, PCB suppliers need to develop the corresponding reliability test requirements.
8. Poor hole plugging

Poor hole plugging is mainly due to the lack of technical capacity of the PCB factory or to simplify the process, Its performance is not full of plug hole, expose copper on hole ring or false copper exposed.
9.Bad size 
There are many possible reasons for the poor size, PCB manufacturing process is prone to shrinkage, the supplier adjusted drilling procedures/graphics ratio/forming CNC program, may cause the mount prone to bias, structural parts with poor assembly. This type of problem can only be controlled by the supplier's good process, so you need to pay special attention to select PCB supplier.
10. Galvanic Corrosion
Appearing on immersion silver board or selective gold-plated+OSP board. Due to a metal displacement reaction between Ag/Au and Cu, the copper under soldermask ink or Au surface will be Concave erosion. Once this problem arises, it is a problem of a batch.

Experienced PCB factory will be through computer software screening this part of the pad, Pre-compensation at design time, and setting conditions in the process to avoid problems occur. So this issue needs to be checked out a good PCB manufacturer.

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