The Principle Of PCB Pressing

Why is the conventional impedance control only 10% deviation? Many friends very much hope that the impedance can be controlled to 5%.

In fact, the impedance control routine is 10% deviation. A slightly stricter one can achieve 8%. There are many reasons:

1. The deviation of the sheet material itself

2. Etching deviation in PCB processing

3. Deviations such as flow rate caused by lamination during PCB processing

4. At high speed, the roughness of the surface of the copper foil, the glass fiber effect of PP, the DF frequency change effect of the medium, etc.

The main purpose of lamination is to combine PP with different inner core boards and outer copper foil through "heat and pressure", and use the outer copper foil as the base of the outer circuit. And different PP composition with different inner plate and surface copper can be equipped with different specifications and thickness of circuit boards. The pressing process is the most important process in the manufacture of PCB multilayer boards, and it must meet the basic quality indicators of PCB after pressing.

1. Thickness: Provides related electrical insulation, impedance control, and glue filling between inner layers.

2. Combination: Provide bonding with inner black (brown) and outer copper foil.

3. Dimensional stability: The dimensional change of each inner layer is consistent to ensure the alignment of the holes and rings of each layer.

4. Board warping: Maintain the flatness of the board.