PCB Technical - What is the PCB solder mask opening and design layout

This article mainly introduces the opening of PCB. First, it introduces openings and bright copper in PCB design. Secondly, it introduces how to realize the tin plating of PCB wiring. Finally, it explains how to set the opening steps.

What is the PCB solder mask opening?

The circuit is covered with a solder mask on the PCB to prevent short circuits and damage to the device. The so-called solder mask opening is to remove the paint layer on the circuit so that the circuit can be exposed to tin.

The golden finger here is to open, and there is a very common function to insert and open the opening, that is, to increase the thickness of the copper foil in the later stage, which is convenient for overcurrent, which is in the power supply board and the motor control board.

Openings and bright copper in PCB design

In the design, customers often ask for openings and bright copper. Because the customer is also ignorant, or is not very clear about this process, communication is very troublesome. In the design, we often encounter customers who need to add shielding on the side of the board, partly bright copper, through-hole open-circuit resistance welding, copper on the back of the IC heat sink, and a scratch pad.

1. Shield

If the customer needs to add a shield, all that needs to be done is to add a Soldmask with a width of at least 1 mm. If you need to add a template, you need to confirm with the customer. While adding the Soldmask, the network copper needs to be expanded in the added mask area, and the Soldmask plane must be covered, otherwise the substrate (FR4, etc.) will be exposed. Other non-local networks should not pass Soldmask. Adding a loose mask area to the PCB effect will show brass. Provide solder mask coverage for unadded areas.

2. Welding mask opening

In the design, it is often heard that the entire board plug hole or partial plug hole. When adding holes, note that the name of the jack company is usually BGA, and vice versa. ). Generally speaking, companies whose specifications exceed 12 mils must use solder mask openings.

3. IC thermal pad

Generally, solder resist PAD (adding a shoulder cover larger than the surface layer or equal to the surface of the surface pad) and ground holes are added to the back of the IC heat sink, and a copper-clad solder mask is placed on the back surface to better transfer the surface layer The heat. The holes in the holes are transferred to the back of the copper skin for better dispersion.

4. Solder touch

In wave soldering, in order to solve the soldering problem caused by the close spacing of the pads, we will use the shape of the scratch pad. Please note that when adding solder mask, copper bumps with the same size as the solder mask must be added.

How to realize PCB trace open circuit

In the circuit, 8 relays need to be driven. When the multi-channel relay is turned on, the current greatly increases. In order to ensure the actual effect, while widening the current line, it is best to remove the solder mask on the current-the green oil layer, and make the circuit board. In the future, you can add tin on the top, thicken the wire, and pass more current.

The implementation method is as follows:

Draw this line in the top layer (or the bottom layer depends on the layer where the preset line is located), and then draw the line to coincide with this in the top solder (or bottom solder) layer.

How to set the circuit to open

CB design can be used to set the opening of the TOP/BOTTOM SOLDER layer.

Top/bottom solder (top/bottom soldering panel green oil layer): The top/bottom solder mask is coated with solder mask green oil to prevent tin on the copper foil and maintain insulation.

A solder mask green solder mask openings can be placed on the pads, vias and non-electric traces of this layer.

In the PCB design, the pad is opened by default (OVERRIDE: 0.1016mm), that is, the pad is raised with copper foil, the outer extension is 0.1016mm, and the wave soldering is tinned. It is recommended not to make design changes to ensure solderability;

2. The through hole in the PCB design is opened by default (OVERRIDE: 0.1016mm), that is, the through hole exposes the copper foil, the external expansion is 0.1016mm, and the wave soldering. If it is designed to prevent tin plating of vias and not expose copper, the PENTING option must be checked in the additional properties of the via SOLDER MASK to close the via.

In addition, this layer can also be used for non-electrical wiring, and the green soldering resistor should be turned on accordingly. If it is located on the copper foil trace, it is used to enhance the overcurrent capability of the trace. When soldering, it can be tinned. If it is on non-copper foil traces, it is usually designed for marking and special character screens, which can save production. Character screen printing.