“Circuit Board Prototyping” PCB Common Failure Analysis

PCB commonly known as printed circuit board, is an indispensable part of electronic components and plays a core role. In a series of PCB production processes, there are many matching points. The board will have defects easily, which will affect thewhole PCB body, and PCB quality problems will emerge endlessly. Therefore, after the circuit board is manufactured and formed, the inspection test becomes an indispensable link. Here are some faults of PCB and solutions.

1 PCB Board Often Delamination In Use

Reason:

(1) Supplier material or process problem.

(2) Poor design material selection and copper surface distribution.

(3) The storage time is too long, the storage period is exceeded, or the PCB is damp.

(4) Improper packaging or storage.

Solution:
Choose the packaging and use constant temperature and humidity equipment for storage. Do a good job of PCB factory reliability test, such as thermal stress test in PCB reliability test. Some responsible supplier use more than 5 times of non-layering as the standard, and it will be confirmed in the sample stage and each cycle of mass production. The general manufacturer may only request 2 times, and only confirm once a few months. The IR test of simulated placement can also prevent more defective products outflow, which is a must for an excellent PCB factory. In addition, the Tg of the PCB board should be selected above 145°C for safety.

Reliability testing equipment: constant temperature and humidity box, stress screening type thermal shock test box, PCB reliability testing equipment

2 Poor Solderability of PCB Board

Reasons:
Too long storage time, resulting in moisture absorption, contamination and oxidation of the layout, abnormal black nickel, solder resist SCUM (shadow), and solder resist PAD.

Solution:
Strictly pay attention to the quality control plan of the PCB factory and the standards for maintenance when purchasing. For example, black nickel, you need to see whether the PCB board production plant has chemical gold, whether the concentration of chemical gold wire is stable, whether the analysis frequency is sufficient, whether there is a regular gold stripping test and phosphorus content test, and whether the internal solderability test has good execution and so on.

3 PCB Board Bending

Reasons:
Unreasonable selection of materials by suppliers, poor control of heavy industry, improper storage, abnormal operation lines, obvious differences in copper area of ​​each layer, and insufficient production of broken holes, etc.

Solution:
Pressurize the thin board with wood pulp board before packaging and shipping to avoid deformation in the future. If necessary, add a fixture to the patch to prevent the device from bending the board excessively. The PCB needs to simulate the mounting IR conditions for testing before packaging, so as to avoid the undesirable phenomenon of plate bending after the furnace.

4 PCB Board Poor Impedance

Reason:
The impedance difference between PCB batches is relatively large.

Solution:
The manufacturer is required to attach batch test reports and impedance strips when delivering. If necessary, provide comparative data on the inner wire diameter and the side wire diameter of the board.

5 Anti-Welding Blistering/Falling Off

Reason:
Solder mask.

Solution:
PCB suppliers should formulate reliability test requirements for PCB boards and control them in different production processes.

6 Avani Effect

Reason:
In the process of OSP, electrons will dissolve into copper ions, resulting in a difference in potential between gold and copper.

Solution:
Manufacturers need to pay close attention to the control of the potential difference between gold and copper in the production process.