The reason of PCB layering:

(1) Supplier material or process problems

(2) Poor material selection and copper surface distribution

(3) The storage time is too long, exceeding the storage period, and PCB board is affected with moisture

(4) Improper packaging or storage, moisture

Countermeasures:

Choose good packaging, use constant temperature and humidity equipment for storage. For example, in PCB reliability test, the supplier in charge of the thermal stress test takes more than 5 times of non-stratification as the standard and will confirm it in the sample stage and every cycle of mass production, while the general manufacturer may only require 2 times and confirm it once every few months. The IR test of simulated mounting can also prevent the outflow of defective products, which is necessary for excellent PCB factories. In addition, THE Tg of PCB board should be above 145℃, so as to be relatively safe.

PCB board plating layer

Under ultraviolet light, the photoinitiator that absorbs the light energy is decomposed into free radical to initiate the monomer to photopolymerization reaction, forming the body molecule insoluble in dilute alkali solution. When the exposure is insufficient, due to incomplete polymerization, in the developing process, the film swelling becomes soft, resulting in unclear lines and even the film layer falls off, resulting in poor combination of the film and copper; If the exposure is excessive, it will cause difficulty in developing, and it will also produce warping and stripping in the plating process, forming infiltration plating. So it’s important to control the exposure energy; The surface of copper after processing, cleaning time is not easy to be too long, because the cleaning water also contains certain acidic substances although its content is weak, but the impact on the surface of copper can not be taken lightly, should be in strict accordance with the process specifications of the time for cleaning operations.

The main reason why the gold layer falls off from the surface of nickel layer is the surface treatment of nickel. The surface activity of nickel metal is poor and it is difficult to obtain satisfactory results. Nickel coating surface is prone to produce passivation film in the air, if not properly treated, the gold layer will be separated from the nickel layer surface. Such as improper activation in the electrical gold-plating, the gold layer will be detached from the surface of the nickel layer peeling. The second reason is that after activation, the cleaning time is too long, resulting in the formation of passivation film layer on the nickel surface, and then go to gold plating, will inevitably produce defects of coating shedding.

Cause of layering of PCB board

The reason:

PCB circuit boards after absorbing heat, produce the different expansion coefficient between different materials and form internal stress, if resin with resin, resin and copper foil stick relay is not enough to resist the internal stress will produce delamination, this is the root cause of the PCB circuit boards layered, and resonant, the temperature of the assembly and the extension of time, are more likely to cause PCB circuit boards layered.

Countermeasures:

1, the selection of the base material to choose as much as possible to ensure the credibility of qualified materials, the quality of the PP material of the multilayer board is also a very key parameter.

2, lamination process control in place, especially for the inner layer of thick copper foil multilayer, should pay attention to. Under thermal shock, PCB board layer appeared in the inner layer of multilayer board, resulting in the whole batch of scrap.

3, heavy copper quality. The better the density of the copper layer in the inner wall of the hole, the thicker the copper layer, the stronger the heat shock of PCB circuit board. Both to PCB circuit board of high reliability, production cost and low requirements, electroplating process control each step requires fine control.

When the PCB board is in the process of high temperature, the copper foil in the hole is broken due to the excessive expansion of the board. That’s a hole hole. This is also the precursor of stratification, which is manifested when the degree increases.

PCB circuit board manufacturers with conditions have their own testing laboratory, which can observe their PCB circuit board performance of heat shock in real time.