Posts Tagged ‘solder mask’

Differences Between Solder Mask and Solder Paste in PCB

Wednesday, December 7th, 2022

When it comes to solder mask and solder paste, there are some engineers confused about their functionalities and even most of laymen thought they are the same, this is not hypothetical, it is real that happened to me. So today let’s explain differences between Solder Mask and Solder Paste for you.

Part 1: What is Solder Mask?

If you had ever seen a printed circuit board, you may see there is a layer of green ink cover on the PCB surface while some orange-yellow areas didn’t cover by ink. In PCB industry, the green ink we called Solder Mask, or abbreviated as S/M, and exposed area is copper, they were leave as GND plane or soldering pads to mount electronic components.

Solder mask is a liquid acrylic oligomer, which has variety of colors such as red, blue, green, white, black. Green is commonly used in the process of PCB manufacturing, so some professional engineers call it as green oil.

Solder_mask

Solder mask applied on the PCB designed as a protection layer to avoid oxidation, corrosion and other environmental impacts when they leave production line. In addition, solder mask between solder pads also can help to prevent forming to solder bridge when assembly.

Below are some other functions of coating a layer solder mask:

  • Prevent physical line breaking of copper trace
  • Only weld in the area that must be soldered to avoid waste of soldering
  • Reduce copper pollution to soldering groove 
  • Prevent insulation deterioration and corrosion caused by dust, moisture and other external environmental factors 
  • With high insulation, so that the high-density circuit is possible

Part 2: What is Solder Paste?

Solder Paste also known as “Solder cream”, is a most important soldering material used in surface mount technology (SMT) process. Mainly function for soldering resistors, capacitors, ICs and other electronic components onto the PCB surface to form a permanent connection.

The solder particles are a mixture of solder formed by mixing solder powder, flux and other surfactants and thixotropic. Traditionally this used to be tin and lead, but with the legislation has been introduced around the world, to only use lead free solders. These may be made from a variety of mixtures, Best Technology commonly used is SAC305 which includes 96.5% tin, 0.5% copper and 3.0% silver, some manufacturers also use 99.7% tin and 0.3% copper, whereas there are other mixtures that include other metals including tin.

Due to the role of solder paste in assembly, solder paste storage is extremely important. However, solder paste got into drying during storing became a common problem faced by most PCBA manufacturers, so How to solve solder paste dry problem is premier.

Solder_paste

Part 3: The Difference Between Solder Mask and Solder Paste

  1. Solder mask is a formal part of PCB, but solder paste ONLY for PCB assembly.
  2. Solder mask is not allowed on the solder pads while solder paste can be printed on the solder pads openings.
  3. Solder mask is used for applying solder mask ink, but solder paste is used for applying paste.
  4. Solder mask has many available colors, but paste mask visually gray.
  5. Solder mask is coating during PCB fabrication, but solder paste is printing when PCB assembly.

With over 16 years in PCB industry, Best Technology is one of the most reliable PCB and PCBA supplier in Asia, we commit to provide high quality products with excellent service before and after sales, to take care our customers wholeheartedly, and to treat customers’ business as ours. At the same time, we keep learning and continually to improve ourselves so that we can catch up the latest technology trend and provide better and better service for our customers.

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5 Views on Explaining Why the PCB Is Green

Wednesday, January 2nd, 2019

At the first sight, you will see that there is a layer of green oil on the PCB. It is called solder mask which is comprised of resin, talc and pigment. Of course, solder mask also has other colors, including red, yellow, black and so on, but green is the one that used the most widely.

When it comes to the question like that “Why are the most of printed circuit boards are green?”, the engineers from Best Technology with rich experience gave 5 points to explain it:

1. There PCB is required to go through the exposure room with yellow light in some processes of fabrication and the visual effective in exposure room is better than the solder mask with other colors.

What’s more, the PCB needs to coat tin, SMT and AOI testing during SMT soldering. All of these processes require optical position alignment and the green solder mask is better for the recognition of instruments.

PCB with green solder mask

PCB with green solder mask

2. Before the flying probe testing is applied widely, most of the wires on the PCB are relied on the naked eyes to inspect.It is very tired to detect the boards in strong light. If the rigid board is green, it will not do a lot harms to eyes.

3. There are cobalt and carbon in  blue and black solder mask,which have a certain conductivity, so there is a risk of short circuit. However, the PCB with green oil will be more friendly to the environment. Because it will not release poisonous gases when use the printed circuit board in a high temperature environment.

printed circuit board with green solder mask

printed circuit board with green solder mask

4. Since some famous brands began to use black solder mask in 2007, such as ASUS and Micro-Star and then people kept an eye on the colors of PCB.In this way, people gradually believe that PCBs with black solder mask means that the boards have high quality.After that, more and more PCB manufacturers started to apply black solder mask. NO one said that printed circuit boards with black solder mask are better than those with green solder mask.It is entirely due to the misleading caused by the famous brands using black solder mask to identify product positioning.

5. There is no reason, just because of habit, so it has been used all the time.

Best Technology is the premier expert in PCB manufacture of electronics, brings a unique combination of technology and quality that offers a competitive supply of printed circuit board and PCBA. With high qualified engineers, we are able to help you find a PCB with high quality. To find out more, contact Best Technology at 0755-29091601 or check the website: https://www.bestpcbs.com/

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