Why is multi-layer PCB prototyping expensive?

Multilayer PCB in communications, medical, industrial control, security, automotive, electric power, aviation, military, computer peripherals and other fields as the "core of the main", the product function is getting higher and higher, PCB more and more sophisticated, the production is also increasingly difficult, the corresponding higher the number of layers of multilayer PCB prototype cost is higher. So what are the difficulties in the production of multilayer circuit boards?

1. multi-layer PCB proofing of the inner layer of the line production difficulties

Multilayer board lines have high speed, thick copper, high frequency, high Tg value of various special requirements for the inner layer of wiring and graphic size control requirements are increasingly high. For example, the ARM development board, the inner layer has a very large number of impedance signal lines, to ensure the integrity of the impedance increased the difficulty of the production of the inner layer lines.

More signal lines on the inner layer, the line width and spacing are basically around 4mil or less; the board layer with multiple core board thin production easy to wrinkle, these factors will increase the production of the inner layer into.

Suggestions: line width, line spacing design in 3.5/3.5mil or more (most factories produce without difficulty).

For example, six-layer board, it is recommended to use a false eight-layer structure design, can be the inner layer of 4-6mil line width 50ohm, 90ohm, 100ohm impedance requirements.

2. Multilayer PCB proofing between the inner layers of the alignment difficulties

The number of layers of multilayer boards is increasing, the alignment requirements of the inner layers are also increasingly high. Film by the workshop environment temperature and humidity will have the impact of the rise and shrinkage, core board production will have the same rise and shrinkage, which makes the alignment accuracy between the inner layers more difficult to control.

3. Multi-layer PCB proofing and pressing process difficulties

The stacking of multiple core boards and PP (version curing sheet) is prone to problems such as delamination, slippage and vapour pack residue when pressed together. The design of the inner layer should take into account the dielectric thickness of the layers, the flow of glue, the heat resistance of the board and other factors in order to design a reasonable lamination structure.

Suggestions: keep the inner layer laying copper evenly, in a large area without the same area laying copper balance with PAD.

4. Multi-layer PCB prototype drilling production difficulties

Multilayer boards using high Tg or other special plates, different materials drilling roughness is not the same, increasing the difficulty of removing glue slag in the hole. High density multilayer board hole density, low production efficiency easy to break the knife, different network over the hole between, hole edge too close will lead to CAF effect problem.

Suggestions: different networks of hole edge spacing ≥ 0.3mm.

These are the above difficulties are the reasons why multilayer PCB prototype expensive, if you have multilayer circuit board need to sample, mass production, PCBA OEM, welcome to contact 2PCB Bella.

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