Knowledge Base

The Complete Guide To PCB Solder Mask

Printed circuit boards, although they look relatively simple, result from a complicated and precise fabrication process.

The PCB board consists of multiple materials and goes through several chemical processes to archive the finished board we all use in our electronic products. One of the processes is covering certain spots on the PCB board with something called a "solder mask pcb."

Although PCB solder masks are often considered an optional process, most if not all PCB fabrication facilities and PCBA manufacturers will offer it by default.

In this article, we will explain what a PCB solder mask is made for, the fabrication process, the PCB solder mask's benefits and features, and the difference between a soldermask in pcb and a paste mask.

This information will enable you to make better decisions for your next PCB or PCBA fabrication and manufacturing project.

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What is solder mask?

Solder-mask is exactly what you imagine it is – a thin layer of pcb soldering at specific spots on the PCB. The solder mask has multiple features and reasons. The main one is to protect the printed circuit board from damage. How to solder to a pcb?

The damages can be environmental, corrosion or oxidation related. Adding a solder mask on the copper layer of the PCB board protects it from all the impacts above and ensures longer shelf life.

The PCB solder mask's primary purpose is to add protection, and under normal circumstances, it will not damage the functionality of the PCB board.

The PCB solder mask also includes extra benefits such as dielectricity (insolation). A circuit designer, however, should not depend on this feature to provide additional safety measurements for the printed circuit board.

A feature often overlooked is that some PCB circuits have a high or tight tolerance. In such a case, the PCB solder mask can prevent unwanted connections, resulting in fewer unforeseen issues during the manufacturing process.

PCB Solder mask type of materials

pcb Solder Paste Printing

If you wonder what solder mask material is made of – there are a few ways to accomplish solder masking for the printed circuit boards. The two most popular methods are Dry film and epoxy liquid.

The epoxy liquid will be most definitely the first choice when it comes to solder mask type of material. The epoxy liquid is the most common material used for PCB solder mask fabrication. It provides a low-price option with excellent quality and long-lasting circuit protection.

If the printed circuit board surface is straight, a dry film material is used as an alternative. Due to the nature of PCB boards, even characters don't often occur, and epoxy liquid is the way to go.

Features of PCB solder mask in PCB design

The solder mask has multiple features, one of the main features is the variety of colors it can come in. Many people assume the green or black color of the PCB comes from the board itself. The reality is that the solder mask plays an essential role in PCB color determination. The PCB solder mask comes in various colors such as Green, Blue, Black, Red, Yellow, Purple, White, etc.

The colors can also come in multiple "finishes," such as glossy or matte finish. Many customers like to choose a black "matte" finish due to its professional durability look—an important thing to note, choosing different colors results in separate price tags. To reduce the cost of the PCB production, the green color is selected by default by most PCB manufacturers unless stated otherwise during the customer order procedure.

Another feature is the PCB solder mask thickness and resolution. The PCB solder mask thickness can go anywhere from 0.2 millimeters up to 1.6 millimeters. The solder mask-designed hole plug can go anywhere between 10 millimeters to 25 millimeters. This gives PCB designers various opportunities and options to consider while designing their next project.

PCB Solder mask and Paste mask – what's the difference?

At this point of the article, we've decided to address the white elephant in the room – the paste mask. Many engineers often confuse paste masks with solder masks and consider them the same. The reason is a misunderstanding of the PCB manufacturing and fabrication process.

As mentioned earlier, a solder mask is a thin layer that adds multiple protection abilities. Those abilities include oxidation, environmental damage, dust, and more. While a solder mask is fabricated during the PCB manufacturing process, a paste mask is used during the PCB assembly fabrication process.

A paste mask is used during the printed circuit board assembly fabrication process to assemble and paste the components to the PCB.

Best way to embed a PCB solder mask in your design

Considering everything we learned regarding PCB solder mask design during the PCB fabrication process, here are the best ways you could embed a pcb masking process in your next creation:

  • PCB Solder mask thickness – consider the thickness based on your PCB design needs: different designs will require different sizes. This is up to the engineer's discretion due to many factors such as space, shape, and heat dispersion.
  • Color – Different applications will require different colors. This decision is most often related to esthetics. If the PCB board is not accessible to consumers, the project is placed inside a closed enclosure, or color isn't a factor in the specific application, a green PCB will be the right way to save cost.
  • Materials – epoxy liquid is the cheapest, but if your PCB is even, you can go with dry film material.

pcb solder mask application methods is different and unique. A single recommendation cannot be made for the best way to embed a PCB solder mask in your PCB design. However, following the best practices and considerations above will prevent unforeseen issues.

Where to buy PCB with the best PCB solder mask

pcba company

While PCBasic offers one of the best PCB assembly services in China, we also provide another type of service. PCBasic one-stop service can provide anything from PCB fabrication to a complete assembly. PCBasic solder mask quality of materials can ensure a great, functional, and beautiful-looking PCB for your next project. If you doubt the pcb soldering is most suitable for your design, don't hesitate to contact us for a quotation.