PCB common bad reasons and analysis

PCB board

In the PCB production process, there are a lot of details that need attention, if not careful,2 oz copper thickness in mm the PCB board will have a variety of problems, resulting in PCB quality problems will be endless. The following collection of PCB common bad reasons, and analyze.

1, PCB board in use often occur in the delamination of bad reasons:

(1) PCB manufacturers of materials or process problems;

(2) PCB design selection and poor copper surface distribution;

(3) The PCB is kept for too long, exceeding the preservation period, and the PCB is affected by moisture;

(4) Improper packaging or preservation of circuit boards, moisture.

Optimization solution: choose good packaging, use constant temperature and humidity equipment for storage.plated through hole vs via Do a good job of PCB factory reliability test, for example: PCB reliability test in the thermal stress test test, the responsible PCB manufacturer is more than 5 times non-delamination as a standard, in the sample stage and mass production of each cycle will be confirmed, while the general manufacturer may only require 2 times, and a few months before confirming once.

There are also simulated placement of IR test can also be more to prevent the flow of defective products, which is generally a good PCB factory must have the process.

Another point is that the PCB board Tg to choose more than 145 ℃, so it is safer, Shenzhen Chin-based electronics in the selection of raw benefits, build a board are basically in line with this feature.

2, PCB board solderability bad reason: placed too long, resulting in the board moisture absorption, the layout was contaminated or oxidized, black nickel appeared abnormal, anti-soldering SCUM (shadow) and anti-soldering on the PAD.

Measures: When shopping for PCB manufacturers to pay strict attention to the quality control program and overhaul of the standards set. For example, black nickel, this need to look at the circuit board manufacturer has no chemical gold outgoing, chemical gold line potion concentration is not stable, the frequency of analysis is not enough, is not set up regular stripping of the gold test and phosphorus content test to detect the internal solderability test is not a good implementation and so on.

3, PCB board bending board warping reasons: circuit board manufacturers choose materials unreasonable, poor control of heavy industry, improper storage, operation of the pipeline abnormalities, the copper area of the layers of the difference between the obvious, break the hole production is not strong enough.

Optimization: the thin board with wood pulp board pressurized and then packaged for shipment, so as to avoid future deformation, if necessary, add fixtures on the patch to prevent the device from overweight bent board. PCB in the package before the need to simulate the mounting of IR conditions for the test, so as to avoid the emergence of the furnace after the board bends the undesirable phenomenon.

4, PCB board impedance bad reason: PCB batches of impedance between the differences are relatively large.

Optimization: Require the circuit board supplier to deliver the batch test report and impedance strip, if necessary, to provide the board within the wire diameter and the board edge wire diameter comparison data.

5, anti-solder blistering / shedding reasons: anti-soldering ink selection differences, the PCB board anti-soldering process has anomalies, heavy industry or patch temperature is too high.

Optimization: PCB suppliers to develop PCB board reliability testing requirements, in different production processes to control.

In order to ensure that the PCB can reach the user intact, in the circuit board production molding, inspection test has become an essential part of the process.

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