Keyboard Builders' Digest / Tips & Tricks
Flexible transparent PCB
PCBWay now offers flexible transparent PCBs, based on PET.
Published September 14, 2022
PCBWay's Gloria reached out to me to announce they started to offer flexible transparent PCBs recently. I'm not entirely sure in the practical benefits of or user cases for such a PCB, but I know some of you are into fully transparent builds for which a transparent PCB may come in handy.
We've seen something similar from PCBBuy, however, their approach was based on glass, which is, well, quite rigid.
PCBWay, on the other hand, came up with a flexible PET (Polyethylene Terephthalate) version – so the same material of e.g. soda bottles. And this is not something experimental but a readily available material choice as it's already integrated in their site.
Thickness
According to this entry on the PCBWay blog, PET is generally 25-125 microns thick, which means it's much thinner than the usual keyboard PCBs (1.6mm) or even other flexible PCBs made of FR4.
Flex and support requirements will be probably completely different compared to usual PCBs and even to flexible PCBs of some 3D scooped models, such as e.g. Quentin's Skeletyl. So you have to keep this in mind when designing PCBs of this thickness.
We know that transparent resin print is a thing in community. It's time to spread out transparent PCB with PET base. Love or hate? #pcb #pcbway pic.twitter.com/Ol6ZhSCjzF
— PCBWay (@PCBWayOfficial) August 30, 2022
Melting point & shrinking
Another thing to consider is melting point. As some of the commenters point out, PET may melt at 60°C, but according to the data sheet of this product, the "solder heat resistance" is 204/288°C. Obviously, this is rather a group of materials than a single specific one.
It was somewhat confusing, for me at least, that there are two different PETs mentioned in the blog post: CPET and LPET, described as halogen-free transparent polyester CVL and CCL, respectively. That's why there are two different melting points.
I was told that the LPET is the transparent board itself, and the CPET is the covering film – probably similar to the solder mask with FR4 PCBs.
The next potential issue is shrinking. For this, there are the dimensional stability values indicated in the tables, which are -0.06 and 0.04 for the CPET, and 0.04 and 0.03 for the LPET – the values are reported as %. (TD is for "transverse direction" and MD for "machine direction", and they are usually measured at 135°C (275°F).)
How to order
I know some of you crazy geeks are looking for the order form already so look no further: here it is (check the "PET (Transparent)" option).
It is already here: pic.twitter.com/kZh5FpuaUX
— PCBWay (@PCBWayOfficial) August 30, 2022
Combined with acrylic, transparent switches, transparent hotswap sockets (and lots of LEDs ofc) a project based on this product may turn out quite stunning.
For those who read this post this far: PCBWay has been offering you a $5 discount for some time. Don't forget to use the KBDNEWS coupon code, and feel free to report back how this works out.
Another option is the 5th PCB Design Contest organized by PCBWay – with a free Raspberry Pi Pico as reward for each participant.
Published on Wed 14th Sep 2022. Featured in KBD #95.
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