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The difficulties in fast proofing of multilayer PCB

In the process of fast proofing of multilayer PCB circuit boards, we often encounter a difficult problem. What are these difficulties? Let’s take a look!

Difficulty 1: Alignment between layers

Due to the rapid development of electronic equipment, the demand for PCB has become more and more sophisticated. More and more electronic products need to use multi-layer PCB. Based on a large number of layers in multilayer PCB circuit boards, users’ Calibration requirements are getting higher and higher.

Generally, the alignment tolerance between PCB layers is controlled at 75 microns. Based on the large unit size of the multi-layer PCB circuit board, the large ambient temperature and humidity of the graphics conversion workshop, the dislocation overlap caused by the inconsistency of different core boards, the positioning method between layers, etc. Interlayer alignment control of multi-layer PCB circuit boards is more difficult.

Difficulty 2: Inner layer production

Multilayer PCB circuit boards use materials such as high TG, high speed, high frequency, thick copper, thin dielectric layer, etc., which puts forward high requirements for internal circuit production and pattern size control. For example, the integrity of impedance signal transmission increases the difficulty of internal circuit manufacturing.

In the process of rapid proofing of PCB circuit boards, the width and line spacing are small, open circuits and short circuits increase, short circuits increase, and the pass rate is low; there are many thin line signal layers, and the probability of inner layer AOI leakage detection increases; the inner core board is thin, easy to wrinkle, and exposed Poor, easy to curl when etching machine; high-level plates are mostly system boards, the unit size is large, and the cost of product scrap is high.

Difficulty 3: Compression Manufacturing

In the process of rapid proofing of PCB circuit boards, many inner core boards and prepregs are superimposed, and defects such as slippage, delamination, resin voids and bubble residues are prone to occur in the stamping production. In the design of the laminated structure, the heat resistance, pressure resistance, glue content and dielectric thickness of the material should be fully considered, and an effective multi-layer circuit board material pressing plan should be formulated.

Based on the large number of layers of the PCB circuit board, the expansion and contraction control and the size coefficient compensation cannot maintain consistency, and the thin interlayer insulation layer is likely to cause the interlayer reliability test to fail.

Difficulty 4: Drilling production

In the process of fast proofing of circuit boards, part of the boards increases the difficulty of drilling roughness, drilling burrs and de-drilling dirt. There are many layers, the cumulative total copper thickness and the plate thickness, the drilling is easy to break the knife; the dense BGA is many, the CAF failure problem caused by the narrow hole wall spacing; the plate thickness easily leads to the phenomenon of inclined drilling.

I believe that many people have encountered these difficulties, but there are always more solutions than problems. There is no problem that cannot be solved. As long as you grasp the core of the problem, you can quickly solve it!


RCY PCB is a professional PCB factory with more than 20 years of professional experience leading process capability in the field of Rigid PCB, Flex PCB, Rigid-flex PCB, etc. If you have any PCB/PCBA demands, feel free to contact us. Email: Sales@szrcypcb.com



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