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- November 17, 2022
- PCB knowledge
- (0)
- 05 mins
How does PCB solder mask work
What is PCB solder mask?
PCB solder mask is also known as PCB solder resist or PCB solder stop. It is a thin polymeric protective PCB layer or coating, which is applied on the traces of the copper, to avoid the initiation of corrosion and oxidation processes, after the process of PCB fabrication. It provides protection against many harmful factors. It is the most authentic way to limit this and enhance the life period of PCB. It has great importance in PCB.
This is coated permanently on the whole circuit of our PCB, so in this way we are saving our PCB for lifetime of it.
The processes of PCB solder masking includes;
(i) Pre-treating
(ii) Coating
(iii) Drying
(iv) Pre-baking
(v) Registration
(vi) Exposure
(vii) Developing
(viii) Inspection
(ix) Final curing.
The application of PCB solder mask
Here are some applications of the PCB solder mask are given:
☆ It stops the corrosion and oxidation processes on PCB.
☆ Lessens the quantity of solder paste needed for the process of soldering.
☆ Boosts the board’s dielectric material break-down voltage.
☆ Protection by environmental contaminants during the handling process.
☆ Enhancement of life period of PCB.
☆ Between board’s components, insulation perform by it.
☆ Metal whiskers production stops by it.
☆ Halt solder bridges making which are unsought connections of PCB board. These bridges cause the shorts in the board which lead to destructions.
Types of PCB solder mask
There are most common kinds of PCB solder mask are given:
★ Epoxy liquid mask
This is cost-effective PCB solder mask type. PCB silkscreened by this. The silkscreen is a printing process that makes ink-blocking fashion by the usage of meshes of different kinds. Mesh permits some open areas that determined for ink-transfer process. It has efficient working.
★ Top-side and bottom-side masks
Mostly engineers use these PCB solder mask to identify the green masks openings that are placed already on PCB. By epoxy, we have enabled the application of this mask. By multiple openings, in board, pins are attached that registered by these masks. At the upper side, the traces are top traces and the mask is top-side (mask). On the other hand, at the bottom, mask is called bottom-side (mask).
★ Liquid photoimeagable mask
This mask is composed of alkali material. It have two liquids mixture. Isolation is present between these liquids but when it needs the mask to apply then mixing (liquids) is done. Due to this, life period becomes enhances. Major advantage of it is that it’s cost-effective. . Many polymer and other solvents are combined in this kind of mask.
Surface finish procedure is not needed by using this mask. It has very high sensation to UV rays. High intensity checking and safe cleaning of the board’s penal is needed just before the usage of mask. After cleaning, we have need to scrub them by various chemical elements. It is very important type of mask.
★ Dry Photoimeagable film mask:
High quality lamination (vacuum) is required before using mask. Just after the utilization, mask is uncovered. Copper pads solderings takes places when patterns are formed by openings. This type of PCB solder masks are beneficial most for the Boards having high-density of wiring.
What is PCB solder mask clearance?
Clearance is also called as tolerance, to conclude that how much the mask is close to the features of the PCB surface. It provides space between the surface features which are called as solder dams. This is play major role in the cessation of solder bridges formation. When we use the conductive patterns that are under 100μm, the clearance may b
What is PCB solder mask opening?
The external layer of PCB lacking the mask are known as PCB solder mask opening. It exposes board’s circuit to tin. Make openings very clear not ambiguous, so that the risk of many harmful events not to be happens like destruction by corrosion. Mostly fabricators choose the openings of PCB solder mask.
What is PCB solder mask coverage or expansion?
A software (EDA) mostly set spacing between board’s solder mask and surface features. This specific working is called as expansion of solder mask. Expansion has three values means it has positive sign when there is a space between mask and outer pad, and negative when mask and pad overlapped. PCB solder mask expansion becomes zero when no gap present between pad and solder mask.How is solder mask applied to your PCB?
There are steps are given for the process of PCB solder mask application to PCB.
1.Cleansing:
Firstly cleaning of board is done and then we dry them for proper working. Contaminants should be properly removed. This first step is very important for the efficient application of the solder mask.
2.Coating of Ink:
Coating of ink is done by using special vertical-coater. We place the board in it. Domain and reliability of PCB determines the coating thickness. This thickness may vary in terms of being incorporated in different portions of circuit.
3.Formal hardening:
In this, the coating of ink becomes solidify.
4.Imaging and hardening
Process of imaging is happens by laser plotted photo-film. UV rays expose when we place panel in front of the film. The area showing opaque, allows the transferation of UV light via film. So, ink under the opaque area becomes hard. We can’t go further without this very beneficial step in the whole sense of solder masking.
5.Develop-mentation
In the developer, board is dipped for the ensuration of properly exposed copper foil. This dipping is mendatory also without this step, our soldering procedure is said to be incomplete.
6.Ultimate processes of cleaning and hardening:
Just before the ultimate surface finish, we have to properly clean and place it for hardening. It is benefited for limiting the risks.
PCB solder mask is a thin polymeric protective layer or coating, which is applied on the traces of the copper, to avoid the initiation of corrosion and oxidation processes, after the process of PCB fabrication. It provides protection against many harmful factors. It is the most authentic way to limit this and enhance the life period of PCB. It has great importance in PCB
Spacing between board’s solder mask and surface features is called as expansion of solder mask. Expansion has three values :positive, negative and zero.
Conclusion
This is very important technique, throughout the fabrication process. It plays very crucial role in the efficient connection and performance of PCB. When we use mask, then wrong connections between different terminals becomes highly lessen.
It is helpful in the limiting the short circuits risks. Good appearance of PCB’s board is due to these solder masks. It proves to be very healthy and beneficial for our board. Every PCB board is required to be coated with this.
