Printed circuit board pressing principle and technology

Why can conventional impedance control only have a 10% deviation? 1oz vs 2oz Many friends very much hope that the impedance can be controlled at 5%, and even I have heard that the impedance requires 2.5%.

PCB pressing process

Platen process must have conditions

Material conditions:

Make an inner core plate with a conductor pattern

Copper foil

Semi-cured sheet

Process conditions:

hyperthermia

High tension

Introduction to polypropylene compacting materials

Features:

Characteristics of semi-cured sheets

rec% (resin content): The percentage by weight of the resin components in the film other than the glass cloth. how to test a circuit board with a multimeter The amount of RC% directly affects the ability of the resin to fill the wire gap, and also determines the thickness of the dielectric layer after the platen.

RF% (resin flow rate) : The percentage of resin output to the total weight of the original semi-cured plate after pressing the plate. RF% is an indicator of resin fluidity, which also determines the thickness of the dielectric layer behind the platen

Vc%(volatile content): refers to the percentage of volatile component loss in the original weight of the prepreg after drying. The amount of VC% directly affects the quality after pressing.

Features:

1, as the internal and external layer of the electronic circuit combined working medium.

2, to provide the appropriate insulating layer thickness, the film is composed of glass fiber cloth and resin, the same glass fiber cloth film after the thickness difference is mainly adjusted by different resin content rather than by the pressing conditions to determine.

3, Impedance control. Among the four main influencing factors, Dk value and dielectric layer thickness are determined by film characteristics, and the Dk value of the film can be obtained by the following formula.

DK = 6.01-3.34r: resin content %

Therefore, the Dk value used in the impedance estimation can be calculated based on the proportion of glass fiber cloth and resin in the laminate film combination.

In fact, the impedance control system is generally 10% deviation, a little more stringent, can achieve 8%, there are many corporate reasons:

1. the plate itself deviation

2. Etching deviation in PCB processing.

3. Flow deviation caused by lamination in the production process of printed circuit board

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

To understand the system impedance, it is necessary to understand the enterprise processing, and the next few articles will take a look at some of their information processing knowledge, and the first one will take a look at the lamination:

PCB pressing principle

The main purpose of the composite is to combine the PP with different inner cores and outer copper foils by "hot pressing", and the outer layer of copper foils as the basis of the outer circuit. The PP composition of different inner plate and surface copper can be adjusted according to the different thickness specifications of the circuit board. Pressing process is the most important process in the production of PCB multilayer board, and the basic quality index of each printed circuit board must be reached after pressing.

1. Thickness: provides the relevant electrical insulation, impedance control and glue filling between the inner line.

2. Bonding: Provides bonding of inner layer black (brown) and outer layer copper foil.

3. Dimensional stability: the size of each inner plate changes consistently to ensure that the holes are aligned.

4. board warping: to maintain the flatness of our plate.