PCB manufacture

=== laser cutter and printer ===
https://www.youtube.com/watch?v=Z228xymQYho I developed a new chemical process to make double-sided PCBs with a laser cutter, and some common chemicals. This is intended to be used on SLA 3D-printed parts, but may work on many materials. 
=== glossy paper ===
http://www.instructables.com/id/DIY-PCB-lab-for-under-3500/?ALLSTEPS I just got the commonly available paper used for printing passport sized photographs. It is extremely glossy on one side. After that I never used magazine paper again. The circuit gets transferred perfectly. I discovered I don't need to soak the paper after heat transfer. Just peeling it from PCB while it is still hot effortlessly removes the toner from the paper. But I've always wanted a way to create solder mask. Without it, solder for ground pads spreads to the ground plane. Also it's hard to get nice conical solder joints as the trace connected to the pad pulls some solder towards it. And it makes the board look real good. :) I'll look for the photoresist film, if only to create solder mask.
=== UV exposure ===
* http://www.instructables.com/id/How-to-make-a-printed-circuit-board-PCB-using-th/
* https://www.youtube.com/watch?v=86G8uma-TD8 Circuit Board Prototyping Part 1: Exposing, Developing, Etching and Tin Plating a PCB. Uses positive developer
* https://www.youtube.com/watch?v=cRCFGZxmob0 Sodium hydroxide removes photosensitive dry film . Film is fixed to pcb and ironed with laminator or clothes iron(100c). Photoresist developer is sodium bicarbonate. Mgchemicals is using this charging 100x more. Place pcb in photoresist solution. The ferric chloride, finally sodium hydroxide. See http://www.instructables.com/id/Dry-Film-Photopolymer-for-making-circuit-boards/
=== Instructables ===
* http://www.instructables.com/id/Toner-transfer-no-soak-high-quality-double-sided/ Uses parchment paper. 12mil clearance obtainable. Well, regarding the toner transfer method, I believe you haven't done everything right. The most important about toner method is to get the board REALLY hot. That means you shouldn't place the board on a cold surface for ironing, instead you should lay it on a piece of wood or on a stack of (news)papers about 5 (2 inch) cm thick such that it insulates well from cold surfaces. In such a way you will get the highest temperature on board. Also, do not raise the iron too many times over the plate, be patient, press the iron on board, as long time as possible. The toner printed paper should get yellowish - that means the temperature was high enough for the toner to melt and stick.
I've had great result even with plain printer paper. Even better results I got with slightly thicker paper from glossy magazines (really!). Just try it and be patient!
Regards!
* http://www.instructables.com/id/PCB-making-guide/ basic guide using glossy paper. Print on oven paper, parchment paper, baking paper. Uses etching solution (in my case Hydrochloric acid + Hydrogen peroxide). Laminator alternative to laser printer.
=== Water protection ===
http://www.mgchemicals.com/products/422a.html Conforming liquids is what you need to look at. They are industrial chemicals for protecting PCBs against moisture. You can make a spray solution out of them and spray the PCB boards of your Ardu Copter. This process is called CURING, which is often used in robotics applications. There are other such chemicals but they are super expensive, so this one was reasonably priced. If you use Brushless motors probabably you need not spraying them. For sonar and other breathing parts, you might want to place a tape or cotton ball when u spray, to avoid clogging them. You also need to follow all the hazmat precautions when handling these liquids during the mixing and spraying. I purchased breathable waterproof fabric and tried to make a jacket for the Ardu copter, and the fabric was too cumbersome to shape. We used shrink-wrap plastic and it worked but the sonar was the issue and before each flight u need to shrink-wrap again. Any membrane will have this problem.
=== PCB outfit === 
http://dirtypcbs.com/index.php pcb全球发货
https://www.wellpcb.com/pcb-quote PCB Prototype and Assembly
https://jlcpcb.com
=== Routing ===
http://electronics.stackexchange.com/questions/125349/what-are-some-tips-to-routing-a-one-sided-pcb For rough routing, I set the grid size to track+space, then it is very quick to lay tracks near each-other, without breaking a Design Rule. I often set the grid 'alt' to an even divisor of that, e.g. if track+grid is 16, then Alt might be 4. That is usually good enough; diagonal corners might be slightly further apart than 'perfect', but it is easy, quick and safe.
=== Links ===
http://www.electricstuff.co.uk/pcbs.html How to make really really good homemade PCBs
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