Why are circuit boards (PCBs) usually green? Many people are curious about this question. This question also has many different answers. Let’s take a look at why most PCBs are green. There are several accepted reasons. let’s have a look.
What is the green part on PCB?
The green part on PCB is called solder mask, and its ingredients are resin and pigment. The green part is green pigment, and there are various other colors, which are no different from decoration paint. The solder mask is paste-like and flowable before it is printed on the circuit board. After printing on the circuit board, it must be “cured” at the end, allowing the resin to harden by heating. The purpose of the solder mask is to protect the circuit board from moisture, oxidation and dust. The only place not covered by the solder mask is usually the pad, which is used for solder paste.
Why are PCBs usually green?
One of the most important reason why most PCBs are green is that green solder mask ink is the cheapest and most mature in the industry. For green ink, for Nanya, the largest ink manufacturer in China, the general price is around 80RMB/1KG, while the price of similar green sun and green matt inks is between 150–250RMB. Green PCBs has the cheaper cost when compared to the PCBs in other colors.
Smaller solder mask viscosity
In addition to the price, the solder mask viscosity of these colors is also different. Green is the smallest, red, yellow and white are slightly larger, and black is the largest. On a high-density PCB, the distance between pads is very small, and the width of the solder mask is smaller. When using screen printing solder mask, solder mask oil with less viscosity is easier to print on the PCB. Therefore, sometimes the PCB that can be made in green color cannot guarantee the quality of the solder mask if it is changed in another color.
Green ink can achieve smaller error, smaller area, and higher precision. Green ink has better properties than inks of other colors. Compared with other color systems, the green series has better characteristics, especially the plugging characteristics of green.
Better visual effect
Generally speaking, the entire electronic board-level products have to go through the process of board making and chip placement. In the board making process, several processes have to go through the yellow light room. The visual effect of green in the yellow light room is better.
Also, during SMT soldering, it has to go through tinning, patching and final AOI verification. These processes all require optical positioning and calibration. The green background color is better for the recognition of the instrument.
Due to the problem of technology, the inspection of many PCB production lines still relies on the workers to see with their naked eyes (of course, most of them use flying probes for testing now). It is a tiring work to keep looking at the board in the strong light. Relatively speaking, green color is the least harmful to the eyes. So most of them use green.
The blue and black are doped with cobalt and carbon respectively, and have certain conductivity, so there is a risk of short circuit. The green PCB is more environmentally friendly, and it will not release toxic gases when used in a high temperature environment.
Is black PCB better than green PCB?
The difference between black PCBs and green PCBs is that the color of the solder mask applied at the end is different. If the PCB layout design and manufacturing process are exactly the same, then the PCB color will not have any impact on performance, nor will it have any impact on heat dissipation.
For the black PCB, because its surface wiring is almost completely covered, it will bring great difficulties to the later maintenance. Black is a kind of color that is inconvenient to make and use, and black PCB is the most difficult to drill holes, so the yield is relatively low. So relatively speaking, the price of black PCB will be a little more expensive. But this doesn’t mean black PCB is better than green PCB. The color alone never cannot represent the performance of the board.
The green part on PCB is called solder mask, and its ingredients are resin and pigment.
- Cheaper cost
- Smaller solder mask viscosity
- Better characteristics
- Better visual effect
- Eye protection
- Environmental friendly
No. The difference between black PCBs and green PCBs is that the color of the solder mask applied at the end is different. If the PCB layout design and manufacturing process are exactly the same, then the PCB color will not have any impact on performance, nor will it have any impact on heat dissipation.