PCB Solder Mask Types – The 4 Types of Solder Masks For PCBs
In order to choose the right solder mask for your project, you must be familiar with its specifications. These specifications specify the hardness, shelf life, and flammability of the product. In addition, they specify the resistance of the solder mask to oxidation, moisture, and biological growth. You may also want to choose a matte or satin finish solder mask, as these can minimize solder beading.
LPI solder mask
In the past, PCB manufacturers would offer two different LPI solder mask types – matte and gloss. Few customers would indicate which one they wanted, so the decision was often left up to the manufacturer. Today, however, customers can weigh the benefits of each type of finish. While there is little difference in performance between the two types of solder mask, a glossy finish may be more appealing to some.
The main difference between these two types of solder masks is their process of application. The first type is a dry film photo imageable solder mask, which is similar to a sticker, except that it is held together by solder. After the soldering process, the dry film photo imageable solder mask is peeled off from one side and the remainder of the material is applied to the PCB mask side-down. The second type is the liquid solder mask, which follows the same procedure without the sticker.
LPI solder masks can be silkscreened or spray-coated onto PCB. These solder masks are most often used in conjunction with Electro-less Nickel, Immersion Gold or Hot Air Solder Leveling surface finishes. For proper application, the PCB should be cleaned and free of contaminants and the solder mask needs to cure thoroughly.
Epoxy solder mask
There are two primary types of epoxy solder masks. One type is made of liquid epoxy that is silkscreened onto a PCB board. This method of solder mask printing is the least expensive and most popular. A woven mesh is used to support the ink-blocking pattern. The epoxy liquid hardens during thermal curing. A dye is then mixed into the epoxy, which cures to produce the desired color.
The thickness of the solder mask depends on where the traces are on the circuit board. The thickness will be thinner near the edges of the copper traces. The thickness should be at least 0.5 mils across these traces, and can be as thin as 0.3 mils. In addition, the solder mask can be sprayed on a PCB for uniform thickness.
Different types of solder mask are available in varying colors. While the most common color is green, other types are available in black, white, orange, and red. Depending on the application, you can choose a color that best complements your project.
Transparent solder mask
There are several types of transparent solder mask available for PCB manufacturing. These are used to protect copper traces from oxidation. These masks also prevent the formation of solder bridges between solder pads. While they don’t provide perfect transparency, they can still be effective for achieving your design goals.
However, the type of solder mask you choose depends on several factors, including the board’s dimensions, surface layout, components, and conductors. You also need to consider the final application. There may also be industry standards that you need to meet, especially if you’re working in a regulated industry. Generally speaking, liquid photo-imageable masks are the most common and reliable option for PCB manufacturing.
In addition to the more common colors, there are also some more unique solder mask types. For example, there are rarer, more colorful masks available, which can be useful for designers and niche electronics makers. The type of solder mask used will affect the performance of the PCB, so it’s important to choose the right type based on your project’s needs.
Graphite solder mask
Different solder mask colors have different viscosities, and the difference is important to know if you’re planning to use one for your PCB. Green solder masks have the lowest viscosity, while black ones have the highest. Green masks are more flexible, making them easier to apply to PCBs with high component densities.
These solder masks offer protection to PCBs and their surface finishes. In particular, they are useful for equipment that requires high performance and uninterrupted service. They are also suited for applications requiring extended presentation life. These solder masks are a time-saving alternative to manual masking with heat-resistant tapes.
Another type of solder mask is dry film photoimageable solder mask. This type of solder mask has an image that is created on the film, and it is then soldered onto the copper pads of the PCB. The process is similar to that of an LPI, but the dry film solder mask is applied in sheets. The process makes the undesired solder mask adhere to the PCB, and eliminates any air bubbles underneath. Afterwards, workers remove the film with solvent, and then thermally cure the remaining solder mask.