PCB News - Circuit board factory: PCB impedance board, can you do it casually

Circuit board factory: PCB impedance board, can you do it casually

To make a long story short, a good PCB impedance board is really not something you can do casually!

Some PCB board proofing factories give a few fixed laminate structures, and then let the customer calculate the impedance according to his lamination... To be honest, for these circuit board factories, the editor really wants to explode! If you can't do it, you can't do it! How can you fool people, and you're so good at fooling people!

To do a good PCB impedance board, you must do the following three most basic points:

One: Engineering data processing.

For manufacturers who really do PCB multi-layer circuit boards, as a customer, you don’t need to calculate the impedance yourself. You only need to mark the single-ended and differential lines that need to control the impedance, and put forward the impedance value requirements. The PCB board manufacturer will The factory parameters help you calculate very well.

1. The material parameters of each circuit board factory are somewhat different.

2. The circuit compensation of each circuit board factory, the potion of etching and electroplating are different.

3. The inspection standards of each circuit board factory are different.

The above three points are destined, it is more reliable if you hand over the impedance to the PCB board factory for deployment! For this point, some PCB board proofing manufacturers ask customers to adjust the impedance and do it directly offline. This is completely irresponsible. This may be no problem for single-ended impedance and individual differential impedance, but for multiple groups such as DDR In terms of impedance, it is not reliable at all!

Two: Line accuracy error control.

The line accuracy is not well controlled, and the impedance deviation is the most common problem of many circuit board factories! To control the line accuracy, the following two points must be met:

1. Good circuit exposure machine, currently the powerful PCB manufacturers use LDI exposure machine, good LDI exposure machine, more than 2 million. This is a threshold for small factories and low-end board factories.

2. Vacuum etching machine. The precise alignment of the circuit exposure is not enough, and when the sulfuric acid solution is needed for etching, the circuit is fully and accurately etched. This requires a vacuum etching machine to meet, especially for some 3-4mil lines. However, the vacuum etching machine has one characteristic while satisfying precise and full etching: the etching efficiency is slow. Low production capacity! This is taboo by conventional Allegro factories!

Three: pressing.

Pressing is very important for PCB impedance boards, especially high multilayer impedance boards! Because the PP dielectric layer will show a state of glue flow under high temperature pressing, at this time, the temperature, process, and calibration control of the pressing are very important! Otherwise, the thickness deviation of the finished dielectric layer will seriously affect the accuracy of the impedance value! Therefore, to determine whether a circuit board factory can make a PCB impedance board, pay more attention to whether they have their own pressing equipment! (The whole set of pressing equipment starts at 3 million yuan, and the maintenance cost is expensive)

In addition to the above points, the editor of Zhongke Circuit also recommends that customers and friends, when placing an order for PCB boards, they can put forward the requirement of attaching an impedance report. This adds a little cost, but it is more guaranteed for impedance control, and it is worth it!

That's it! Today I will share so much with you! I wish everyone a smooth PCB board production, thank you!