PCB thickness uneven

Vacuum laminating machine, reducing the pressure to reduce the flow of plastic, try to keep more amount of resin, because the resin affect εr, resin save more, εr will be lower. Lamination thickness tolerance control. Because PCB circuit plate board thickness is uneven, it indicates the dielectric thickness change will affect Z0。

In strict accordance with customer requirements PCB board cutting plate model, the wrong model, εr wrong, wrong thickness, PCB manufacturing process all right, the same scrap. Because Z0 by large εr affect finished plywood to avoid absorbing water, because water εr = 75, for Z0 will make a big decline and instability effects。 

Z0 value Ban Ban PCB solder line will reduce signal lines 1 ~ 3Ω, theoretically solder thickness not too thick, in fact, the impact is not great. Copper wire surface in contact with air (εr = 1), so that the measured value is higher Z0. But after the solder test Z0 value will drop 1 ~ 3Ω, because the solder is εr of 4.0, much higher than the air。 

Be sure to find out the inner plate wire gap and protruding opening of 2GHZ high-speed signals, even if the gap of 0.05mm must also be scrapped; inner width and defect control is the key。