Differences

This shows you the differences between two versions of the page.

--- pcbetching [2022-01-16 11:41] – jtdburton
+++ pcbetching [2022-01-19 20:58] – [Developing] jtdburton
@@ Line 16: / Line 16: @@
 Sodium hydroxide ("drain cleaner"/photonegative stripper): Highly caustic. Wear gloves. Can be flushed down the drain (it's drain cleaner).
-Ferric chloride (etchant): Wear gloves. Wear eye protection. Touch it and die. Can be reused for months or even years, so you shouldn't need to dispose of it; if you do, there's a tub under the sink for the used stuff. DO NOT flush down the drain.
+Ferric chloride (etchant): Moderately corrosive, strong skin and eye irritant, toxic if consumed, toxic vapours. Wear gloves. Wear eye protection. Open a window and/or switch on the air filter. Can be reused for months or even years, so you shouldn't need to dispose of it; if you do, there's a tub under the sink for the used stuff. DO NOT flush down the drain.
 ===== Design/file prep =====
@@ Line 29: / Line 29: @@
 Use your image editing software of choice to prepare your cut file for lasering. It needs to be a vector with all shapes as outlines and no fill, and it needs to be mirrored either in your image editor or once you import it into the LaserCut software.
-Place your workpiece in the laser cutter copper side DOWN. Cut settings may need some experimenting to get right. The aim is to cut all the way through the substrate without hitting the copper hard enough to cause lots of sparks. My best results have come from using the big laser with speed 35, power 60, corner power 50 on 1.5mm board.
+Place your workpiece in the laser cutter copper side DOWN. Cut settings may need some experimenting to get right. The aim is to cut all the way through the substrate without hitting the copper hard enough to cause lots of sparks. My best results have come from using the big laser with speed 25, power 60, corner power 50 on 1.5mm board.
 Run the cuts. Give it a couple of minutes before you open the lid, vapourised FR1/2 isn't as bad as FR4 but it's still unpleasant.
@@ Line 39: / Line 39: @@
 {{:20220115_113716.jpg?400|}}
-===== Exposure ====
+===== Exposure =====
-Grab the laminator, some sellotape, and a pair of scissors from G1 before you start with this section.
 Currently (as of January 2022) the lab has NEGATIVE photoresist, which means the copper will be removed from the areas of your board NOT exposed to UV light.
-In the past the recommendation has been to use transparencies run off the laser printer for UV masking. This does not actually work very well because the "black" areas do not come out fully opaque. Tracing paper may work - as of this writing we don't have any. One good way to produce a UV mask in the absence of proper printables is to laser-cut your trace pattern into a scrap bit of very thin plywood or black acrylic.
+The best option for creating your UV mask is to print it onto some heavy tracing paper on the laser printer in G1. You may need to print and overlay two copies.
+{{:20220118_211802.jpg?400|}}
+You can also cut your trace pattern into a scrap bit of very thin plywood or black acrylic.
 {{:20220115_112643.jpg?400|}}
+Either way, once you have your mask ready, grab the laminator, some sellotape, and a pair of scissors from G1.
 Cut a piece slightly larger than your board from the roll of photoresist film kept wrapped in a black bag in the cabinet in G14. PUT THE ROLL BACK IN THE BAG - it's UV sensitive.
@@ Line 65: / Line 69: @@
 Make a solution of about 500ml water and 20g washing soda crystals (sodium carbonate decahydrate). There is a handy 3D-printed scoop to help you get the right amount of washing soda.
-Immerse the PCB in the solution for a few seconds, then remove it. You should now be able to easily peel off the transparent film on the front. Return the board to the solution and start gently brushing it with the paintbrush. You should notice bits of the blue mask coming off. Once all the copper you want to remove is exposed (this should take about 30-60 seconds), remove from the solution and rinse with plenty of water.
+Immerse the PCB in the solution for a few seconds, then remove it. You should now be able to easily peel off the transparent film on the front. Return the board to the solution and start gently brushing it with the paintbrush. You should notice bits of the blue mask coming off. Although it might look like all the unwanted copper is exposed after a minute or so, it actually takes about three minutes for the film to fully develop. After that time has passed, remove from the solution and rinse with plenty of water.
 {{:20220115_121125.jpg?400|}}