Photoresist circuit boards play a crucial role in the production of electronic devices. Also, photoresist is a crucial material used in PCB. This article seeks to explain everything you need to know about photoresist PCB.
What is Photoresist?
A photoresist is an important material used for fabricating PCB boards. Also, this material is light-sensitive and widely used in photoengraving and photolithography. The photoresist is a basic material that comprises a solvent, sensitizer, and a polymer.
Each of these elements plays a crucial role. For instance, the solvent enables the photoresist to spin and create thin layers over a surface. The sensitizer regulates the photochemical reaction in the polymer stage. Also, the polymer alters the photoresist’s structure when subjected to radiation.
In addition, photoresist plays a significant role in the production of IC devices. The photoresist and photolithography development makes it possible to shrink the circuits’ size. Photoresist serve as a major step for fabricating PCBs.
Also, it is a form of coating that changes when exposed to UV light. In addition, this material acts as a masking layer for etching. Also, Photoresist is majorly classified as negative and positive.
In a negative photoresist, the part of the photoresist exposed to light is insoluble. The photoresist developer dissolves the unexposed part of the photoresist. In this type of photoresist, UV light exposure results in photoresist polymerization. Hence, the negative resist is on the surface of the substrate. Also, the photoresist developer eliminates the unexposed areas.
Here, the polymer weakens due to the photochemical reaction during light exposure. Therefore, this makes it more soluble. The unexposed part of the photoresist is insoluble to the developer.
Both negative and positive photoresists play a crucial role in PCB manufacturing. Negative photoresists have a shorter processing time. Also, they are good adhesion to silicon. However, positive photoresists are thermally stable. Also, they have better resolution.
What is a Photoresist PCB?
A photoresist PCB is a high-quality photoresist coated PCB ideal for several applications. This PCB is ideal for manufacturing double-sided PCBs. All materials used for photoresist PCBs are high quality. The fabrication of photoresist PCBs involves the use of ultraviolet light. The photoresist in this PCB features a dye. This dye offers a good contrast against the copper. Therefore, a light-proof blue film protects the PCB. Hence, you can guillotine then without fracturing the photoreist.
The photoresist PCB features a blue film coat which enable lights protection. Therefore, this enables the board before the film removal to be handled during the day. A photoresist board shields the copper. A photoresist PCB is dip-coated with a positive photoresist.
Also, a photoresist PCB is thermally stable. Also, this PCB has a good dielectric constant and coefficient of thermal expansion. Therefore, this PCB has great electrical and thermal properties. A photoresist PCB is a light-sensitive circuit board ideal for use in several applications. Also, this PCB features great benefits.
Photoresist PCB Fabrication Process
You need to draw out the PC B schematic. There are several schematic program that can help you to achieve this. After drawing the layout and schematic, print the layout. Turn on the Vias, top layer, dimension, and pads to print the desired board. Once the layout is ready for printing, ensure the texts correctly indicate after transferring it to the board.
UV light exposure
Here, the presensitized PCB must be exposed to UV light. Put the printed transparency on the plastic above the LEDs. Ensure the ink is facing up. Remove the white film from the presensitized PCB. Also, this will expose the photoresist. After, put the PCB on the transparency with the photoresist facing the LEDs. Ensure you press the photoresist against the transparency’s ink.
Turn on the UV light box. The photoresist will have the same look after exposing it to UV light. Also, you won’t be able to differentiate between the non-exposed and exposed board.
Developer solution preparation
Here, you will prepare the developer solution. Ensure you mix the solution thoroughly before putting the PCB in the solution. It is advisable to use tap water to mix the solution. After this, shake the PCB around. The photoresist’s parts exposed to UV light will wash away. Avoid leaving the board in the solution for too long. Also, the photoresist will wash away otherwise. Put the PCB in cold water to halt the reaction.
A solution of hydrogen peroxide and muriatic acid will help to etch the copper away.
Use a Q-tip and Acetone to remove the photoresist. Also, the photoresist will easily come off. Use the Q-tips till they are white.
Here, you will have to populate your PCB with different components.
The Chemical Structure of Photoresist
However, photoresists are in three categories according to its chemical structures.
This is a photoresist that can crosslink when subjected to light. It can produce an insoluble network. Also, this type of photoresist is ideal for negative pohotoresist.
This is a photoresist that can produce free radical when subjected to light. Also, it starts monomer potopolymerization to generate a polymer. However, this type of photoresist is useful for negative photoresist.
Photodecomposing photoresist produces hydrophilic products when exposed to light. Also, this type of photoresist is ideal for positive photoresist. An example of this photoresist is azide quinine.
Frequently Asked Questions
How do you remove photoresist?
You can remove photoresist in three ways. The use of organic solvent can help to remove photoresist. Also, another way to remove it is by using some inorganic solvents. Here, the organic carbon in the photoresist oxidizes to carbon dioxide and removes. The last method is by using plasma to strip off photoresist.
Where is photoresist PCB ideal for use?
Photoresist PCB is ideal for use in several applications. This PCB is useful in consumer electronics, medical devices, and more.
This article has provided well-detailed information on photoresist PCBs. It discussed how to fabricate photoresist PCBs. Also, it talked about the different types of photoresist.