Photolithography and the Similarity to Screen Printing

In class this week, we used photolithography to create a circuit board. According to Wikipedia, the most reliable of web sources, photolithography is also known as optical lithography or UV lithography. It is defined as “the process of transferring geometric shapes on a mask to the surface of a silicon wafer” by gatech.edu. I took some pictures during the assignment of the process.

I really enjoyed this assignment, partially because of its familiarity. I’ve worked with my parents for many years at their business, and one of the services they offer is screen printing. We print garments (such as t-shirts, sweatshirts, sweatpants etc.) and textile goods (such as tote bags, towels etc.). Many people are familiar with the concept of screen printing. It is “a printing technique whereby a mesh is used to transfer ink onto a substrate, except in areas made impermeable to the ink by a blocking stencil”. However, few people are familiar with the process that is taken to prepare the screens to print with.

First, the screen needs to be coated with emulsion. This is a light-sensitive “goop” that is applied to the surface of the screen. When this emulsion is exposed to light, it hardens, so preparing the screens is done in a dark room. After the screen has been prepared, a piece of clear film is placed on it. This is similar to the “mask” we used in class. The image area is printed in black to prevent the light from passing through, while the surrounding film is transparent to allow light to pass and harden the emulsion. This screen is then placed in an exposure unit to do just that. This was similar to the UV process that we used during our lab on Monday. After the screen is finished in the exposure unit, it is taken to a wash out booth to be cleaned. A pressure washer is used to clean the unexposed emulsion out of the screen, revealing the image area. Now the screen is ready to be used.

I enjoyed seeing a scientific process that so closely paralleled what I do on a regular basis.


Works Cited

"Photolithography." Photolithography. Gatech, n.d. Web. 03 Oct. 2015. 
"Photolithography." Wikipedia. Wikimedia Foundation, n.d. Web. 03 Oct. 2015. 
Reuels. "Reuel." Silk Screen Printing Instructions. Reuels, n.d. Web. 03 Oct. 2015. 
"Screen Printing." Wikipedia. Wikimedia Foundation, n.d. Web. 03 Oct. 2015.
YarisWorks. "How to Silk Screen." Instructables.com. Instructables, n.d. Web. 03 Oct. 2015.