Back Drilling Technology in PCB Production

Friends who have done PCB design know that the design of PCB vias is actually very particular. Today, I will explain in detail the back-drilling technology in the production of PCB circuit boards.

1. What PCB back drill?

Back drilling is a special kind of deep hole drilling. In the production of multi-layer boards, such as the production of 12-layer boards, we need to connect the first layer to the ninth layer. Usually, we drill through holes (one-time drilling), Then sink copper. In this way, the first layer is directly connected to the 12th layer. In fact, we only need the first layer to be connected to the ninth layer. Since the 10th to 12th layers are not connected by lines, they are like a pillar; this pillar will cause signal integrity problems and need to be connected from the The reverse side is drilled off (secondary drill). That's why it's called back drilling.

2. Advantages of back drilling

1) Reduce noise interference;

2) Improve signal integrity;

3) The local plate thickness becomes smaller;

4) Reduce the use of buried blind vias and reduce the difficulty of PCB fabrication.

3. What is the role of back drilling?

The function of back-drilling is to drill out the through-hole section that does not play any connection or transmission function, so as to avoid reflection, scattering, delay, etc. caused by high-speed signal transmission.

4. Working principle of back drilling production

When the drill pin is used to drill down, the micro-current generated when the drill pin touches the copper foil on the substrate surface senses the height position of the board surface, and then drills down according to the set drill-down depth, and stops when the drill-down depth is reached.

5. Back drill production process

a. There are positioning holes on the PCB, and the positioning holes are used to locate and drill the PCB;

b. Electroplating the PCB after a drilling hole, and dry film sealing the positioning holes before electroplating;

c. Make the outer layer graphics on the PCB after electroplating;

d. Pattern electroplating is performed on the PCB after the outer layer pattern is formed;

e. Use the positioning hole used by a drill for back drilling positioning, and use a drill tool for back drilling;

f. Wash the back-drilled holes with water to remove the remaining drill cuttings in the back-drilled holes.

6. Application field of back drilling plate

Backplanes are mainly used in communication equipment, large servers, medical electronics, military, aerospace and other fields.