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It’s not easy to make a good impedance board. Some sampling factories layout a few fixed laminating structures and then let the customer choose according to his laminating, calculate impedance. These board factories cannot do a good impedance PCB.
To complete a good impedance board, we should check the following 3 aspects
PCB Engineering processing
As a customer, you don’t need to calculate your impedance for a trustworthy multiplayer manufacturer. What you need is to control the impedance of the single-terminal, the difference line marked, and the impedance requirements.
We will calculate the impedance for you according to the parameters of our factory. But different PCB factories make impedance boards that differ in the following ways:
- PCB material parameters vary from factory to factory.
- Each factory PCB circuit compensation, etching plating potions are different.
- PCB inspection standards are different.
The above three points are doomed that you give the impedance to the PCB board to the factory deployment is more reliable. And for this, some sampling factories ask the customers to adjust the impedance, then arrange the production directly, which is completely irresponsible. Single-ended impedance boards or individual differential impedance may be OK, but it simply cannot do it for DDR and other multi-group impedance.
PCB circuit precision control
PCB circuit precision control is not reasonable, and impedance deviation will be the most common problem in many plants. Two kinds of machines can control the accuracy of the PCB circuit:
1. LDI PCB exposure.
At present, powerful PCB manufacturers use LDI exposure machines.
Good LDI exposure machines cost more than 300,000 US dollars, a threshold for small and low-end plate factories.
2. Vacuum etching machine.
The accuracy of line exposure alignment is not enough. It also needs to etch the line fully and accurately when etching with the sulfuric acid solution. However, for some 3-4mil lines, the vacuum etching machine meets the requirements of accurate and full etching and has one disadvantage: slow etching efficiency and low production capacity. This is unacceptable to PCB sampling factories.
PCB lamination
Lamination is very important for the impedance boards, especially for the high multilayer impedance PCBs. Because the PP layer in high-temperature pressure will appear in the state of flow, at this time, for the force of temperature, process, calibration control is very critical. Otherwise, the thickness deviation of the finished dielectric layer will seriously affect the precision of the impedance value.
Therefore, let’s pay more attention to whether the PCB factories have their lamination equipment, and then determine if they can do a good impedance board. The total lamination equipment costs about $500,000, and maintenance is expensive.In addition to the above, we suggest customers ask PCB factories‘ impedance reports to do boards, which adds a little expense, but it’s worth it for better assurance of impedance control.
Please get in contact with YooProo freely for any impedance PCB quotes.
