PCB News - Five ways of saying black ink on PCB circuit board, which one do you think is reliable

Five ways of saying black ink on PCB circuit board, which one do you think is reliable

Since the iPhone (Apple) era, mobile phones have almost all used black PCB circuit boards. What prompted this change? What is special about the black PCB circuit board?

Statement 1: In the process of washing PCB circuit boards, black PCB boards are the most likely to cause chromatic aberration. If the raw materials used by the PCB circuit board manufacturer and the self-made process slightly deviate, the defective rate of PCB boards will increase due to the chromatic aberration. high. So, what should we do?

Zun: First of all, I have never touched the circuit board proofing manufacturer to tell me the problem of color difference. Chromatic aberration is not an item evaluated by customers, and it is difficult to quantify. In addition, compared with black, other colors are more likely to cause chromatic aberration. Because there is one kind of black, as much black as possible is enough, and there are many other colors. For example, green has:

Statement 2: As the circuit traces of the black PCB circuit board are difficult to identify, it will increase the difficulty of later maintenance and debugging. Generally, if there is no brand with profound RD (R&D) designers and a powerful maintenance team, black PCB will not be easily used. Yes, this is why only a few high-end brands (such as ASUS) use black PCB boards for the high-end series-it can be said that the use of black PCB proofing is a brand's confidence in the RD design and post-maintenance team. From the side,, Is also a manifestation of circuit board manufacturers' confidence in their own strength.

Zun: This statement is nothing short of serious nonsense, and it makes sense.
First of all, Debug has drawings, self-developed circuits, when debugging, you can read the drawings if you can’t see clearly. Besides, whoever finds a signal can find it entirely on the PCB board.

Statement 3: To prevent plagiarism
Yu: Brother, have you made 4-layer boards, 6-layer boards, 8-layer boards, 10-layer boards...20-layer boards? Even if it is made green, do you see the line with your eyes?
Do you know a multimeter?

Statement 4: Increase maintenance costs. Although black PCB boards are not necessarily high-end products, the use of black PCB boards reflects a manufacturer's confidence in their products and also reflects their careful workmanship. Because the follow-up repairs of products made with black PCB boards are relatively difficult, if the quality is not good enough, the follow-up repair costs will be very high. Therefore, products using black PCB boards are generally designed independently, and only high-end products that have confidence in product quality will be used. In order to reduce maintenance costs, the quality control of products using black PCB boards will be more stringent, which can improve the utilization rate of the good products of the circuit board products.
Xian: The person who designs the circuit will not be cheap. It will not increase maintenance costs just to pretend to be forced. There are tools for maintenance, not by eyes. I can see where there is a problem with the circuit with my eyes, and I was sent to Zhongke as a research object. Generally, the masters in the electronics market are modular replacements. Even if the chips are changed, they will not be traced by observing the PCB, mainly relying on tools and experience.
Just imagine: Apple maintenance workers in the electronics market, do they look for pads with the naked eye.
Do you confirm the green board and find the line with the naked eye?

Statement 5: Good heat dissipation? The reason why black oil is used is actually because black oil dissipates heat better than any other color oil. Everyone only knows that black objects absorb heat better. In fact, from the theory of heat radiation, heat dissipation is the same as heat absorption. The darker the color and the rougher the surface, the better the heat radiation, so many heat sinks are made black. This is the reason why refrigerator condensers and compressors are all black.
Xun: Black is good for heat dissipation, but your PCB itself is so hot, your design is enough.
According to the classic radiation law of physics-the radiation power of all objects is equal to its absorption power, and the absorption power of a non-black body is always less than that of a black body at the same temperature. Therefore, comparing the heat dissipation capacity of non-black and black objects under the same conditions, black objects dissipate heat significantly faster, and the darker the color, the higher the emissivity and absorption rate of heat energy.
Finally, black absorbs all the light and naturally absorbs heat more than white under the same conditions. However, according to the classic radiation law, black objects absorb heat faster and dissipate faster, so when it absorbs too much heat, it will emit equal heat., So that it can absorb more heat.
If your PCB needs to dissipate heat, it will brighten the copper, and also use aluminum substrates. Copper substrates are not black. In fact, the color is negligible compared to the measures of other dimensions.
If the MOSFET needs good heat dissipation, the pad on the front side will be enlarged and the solder mask on the back side will be removed.

1. The cost of black PCB is indeed more expensive than the cost of green. Some manufacturers charge a fee for color.
There are two reasons:

Reason 1. There are more users who choose green, so green is relatively cheap, so some fees need to be charged for other colors.
Reason 2. All boards with a batch and solder mask color of black need to be tested! It is more difficult to find the problem because of the visual inspection of the surface processing error.
During the PCB assembly process (pcb assembly) there is visual inspection (visual inspection). Human vision is very prone to visual fatigue to yellow, red and black. Let you test 6000 pcs black PCBA on Foxconn assembly line 12 hours a day.
It is said that the Apple production line does not have this link of visual inspection (to be verified), and should mainly rely on automatic optical inspection machine (AOI) and non-destructive flaw detector (X-Ray)

2. Because we are accustomed to green PCB boards, we chose green paint as the material for PCB solder mask because of a coincidence. But if 90% of the PCBs in the world are black, it is estimated that people will think that black is so ugly, but green is taller.
It is estimated that Jobs has such a strong obsessive-compulsive disorder because he likes the strong contrast between black and bright gold of the pad, so he chooses black uniformly. In fact, the iPod has always been green.
The use of black PCB has nothing to do with high-end, it is just a style of designer.
These blade servers of telecommunications are all priced in the tens of thousands or even hundreds of thousands, and they are often green.
3. The black PCB is not easy to be found inside the product. This is a fact. If you are particularly concerned about this, let's just make a reason.

In addition, the "completely open source" open source hardware crowdfunding launched by Hard Ten is also the black of choice. Because the black PCB convention has become synonymous with quality. The bright white silver tin of the chip solder joint is highly contrasted with the black of the printed board and chip package, just like the dazzling stars at night.