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Items:PCB Etch Set

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Item: PCB Etch Set
42001
350x350px
Status: Usable
Owner: Johan
Location: Brixel HQ
All allowed to: Use Borrow Research Repair 
If asked allowed to: Modify Hack 
Edit tags: PCB Etch Set


This PCB Etch set is used for photo-resistive laminates.

Contents

The PCB etch set contains:

  • A: Timer module
  • B: Small suitcase containing UV lights
  • C: Two (2) trays to develop and rinse PCBs
  • D: Etch tank (~23cm x ~19cm) with PCB holder (~23cm x ~17cm)
  • E: Aquarium heating element
  • F: Chemicals to develop (SodiumHydroxide) and to etch (SodiumPersulfate) with a spoon
  • G: Some blank (undeveloped) PCBs

You will need a scale to measure the weight of the chemicals and something to measure an amount of water.

You will need your design printed on transparent slides.

Optionally you can use an air (bubble) pump to agitate the etch fluid in order to speed it up and to make sure the PCB is evenly etched.

It is advised to wear (surgical) gloves when working with these chemicals.

How to use it

Please read all steps through before starting!

If you peel off the protective layer of an unexposed PCB, it should be exposed as soon as possible. (Sunlight is not good.)
An exposed PCB should also be developed as soon as possible.

It is advised to etch the PCB immediately after developing.

Design

PCB design on transparent slide

Print your PCB design on a transparent slide. Laserprinters work best for this.

Do print the design mirrored, even if it looks simple to turn the slide around, your resolution will be less during the exposure process.

1200dpi is a nice resolution for a detailed PCB.

Exposure

PCB ready for exposure
Press start...

Place your design on the glass with the inkt on top, closest to the PCB. (This is why you needed to print a mirror image.)

Peel off the protective layer of the unexposed PCB and place it on top of your design.

Close the suitcase, be sure the PCB has not moved.

Set the timer module to "Auto" and press the "Start" button. The UV lights will turn on for about 4 minutes. Then you PCB has been properly exposed.

Do not look into the UV light...

Developing

This is how it should look like after developing...

Wear gloves.

Prepare a tray of water with SodiumHydroxide (Dutch: NatriumHydroxide).
You will need 10g per liter water. (The tray can not contain 1L of water, so do the math.)
(More will make developing go faster, but also increases the risk of overdeveloping.)

Prepare another tray with peferably destillated water.

Place the exposed PCB in the developing solution, and keep agitating it a little.
After a while (1-2 minutes) your PCB layout will become visible.

When the PCB layout is clearly visible (even the smallest details), your can take out the PCB and rinse it in the other tray.

If you detect, after rinsing, the PCB is not yet properly developed, you can develop it further.
It is better to check and develop some more than to have the PCB overdeveloped!

The end result should be a PCB with your design clearly visible on it. Everything else should be copper. If there is still no copper visible in places there shouldn't be any traces, develop a little more. The developed PCB should be the exact opposite of what you want to have.

Throw away the developing fluid after use. You can not keep it for very long (days). (It is OK to develop many PCBs in a row though.)

Etching

PCB in PCB holder, ready to be submerged.

Definitely wear gloves.

Prepare the etch tank with a solution of 200-250g SodiumPersulfate (Dutch: NatriumPersulfaat) per liter water. Do not fill the tank completely, just make sure your PCB will be completely submerged.

Add the aquarium heating element and turn it to the max. The heating element will go the 32° C, but unfortunately etching is more efficient at 45-50° C. (At lower temperatures, it will just take longer.)

When the etch tank is warmed up, you can proceed.

Place your (dried) PCB in the PCB holder and insert it into the tank. For very large PCBs, or many at ones, you can drill a hole in hte PCB and hang it with a wire in the thank.
From time to time you can wiggle the PCB(s) a little.

Optionally you can connect an air (bubble) pump so the etching fluid is wiggled automatically.

After a while the copper that was visible will start to dissolve into the fluid.
This is good. ;-)

Continue etching until all visible copper is disolved, but no longer! If you "over-etch", you will start dissolving you PCB traces.

Done!
(Rinse it with water.)

You can keep the etch fluid for a next time, but over time the fluid will become less and less efficient as it will contain more and more dissolved copper. Because the fluid is irritating, it is best to keep it in closed, but clearly labeled, bottle.

After care

Removing the top layer

The traces on your PCB are still covered by a layer of material due to the developing process. This is no problem, as it will vanish with enough heat during soldering. This layer will also protect the traces against oxidation.

However, if you wish to get rid of it, now is the time by using a light abrasive material. (Abrasive sponge, etc...)

If you remove the protective layer, add a new one if you want your PCBs to last... (Ex: Plastik 70, etc...)

Size

PCBs are a very hard material!

Do not lasercut!

You can use a saw, or a heavy duty (metal) shear or tin snips.

Drilling

Most PCBs are FR-4 (glass epoxy) and this is a very hard material!

Use a hard drill-bit, and a drill stand.
Your drill-bits will break if you try to drill by hand.

Use protection when drilling FR-4 PCBs!
It is better to use FR-1 (phenolic cellulose paper) for hand manufacturing.

Ideally, your drills should be 0.1mm bigger than your components.


Dual-Sided PCBs

Create 2 designs, top and bottom layer, and develop/etch them separately on thin (0.5 mm) PCBs.

Drill 2 or 3 holes in both PCBs individualy in places that actually require holes completely through. (Through-hole components, vias, etc...) Use these holes to align both PCBs and glue them together with superglue.

When glued and aligned, you can start drilling all holes in one go.
(If you drill both layers separately, the layers will not align very well...)

Vias can be created by soldering a small wire in place.