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Old 1st February 2013, 07:01 PM   #1
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Default Confused about this step in the soldermasking process

I'm watching this video here:

Apply a Solder-Resist Mask to PCBs (Printed Circuit Boards) - YouTube

It seems like before applying the soldermask, the board is already etched. The part where I am confused is where he applys the solder mask, then UV exposes the pins/pads on top of the solder mask. Then develops the mask without the pins/pad covered in soldermask.

1. Is this correct? I thought you can only UV develop with photoresist coding? But he uses soldermask lacquer.

2. Also, is there any common product you can get (say at home depot or ace) in place of the solder mask lacquer?

3. What solution is he using to develop the solder resist?
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Old 1st February 2013, 08:49 PM   #2
JMFahey is offline JMFahey  Argentina
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Quote:
Originally Posted by Fusion916 View Post
I'm watching this video here:

Apply a Solder-Resist Mask to PCBs (Printed Circuit Boards) - YouTube

It seems like before applying the soldermask, the board is already etched.
Yes, or it would be imposible to etch afterwards.

Quote:
The part where I am confused is where he applys the solder mask, then UV exposes the pins/pads on top of the solder mask.
In reality she exposes "everything-but" the pins pads, which are covered by an opaque mask.

Quote:
Then develops the mask without the pins/pad covered in soldermask.
You need an opaque mask only during exposure.

Quote:
1. Is this correct? I thought you can only UV develop with photoresist coding? But he uses soldermask lacquer.
There's TONS of chemical products hardened or weakened under UV light.

Quote:
2. Also, is there any common product you can get (say at home depot or ace) in place of the solder mask lacquer?
No, not Home Depot, but I would experiment with Silk Screen Emulsions.
Can't be very different.

Quote:
3. What solution is he using to develop the solder resist?
Dunno, the video shows a kit, including everything, even gloves and brush.
Each Manufacturer suggests the optimum process for his product.

Personally, this method looks somewhat crude to me, not quite uniform layer and slow, suitable only to test prototypes.

I silkscreen 2 component epoxy "Soldermask Ink" which is much faster, but justified only over, say, 50 PCBs.

There is a "photoimageable dry etch resist" film, which is what the Pros use, but it's beyond my league.
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Old 1st February 2013, 11:09 PM   #3
HighTec is offline HighTec  Croatia
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The developing solution is 10 grams of soda carbonate (washing soda) mixed in 1 liter of water. Well, like JMFahey has already mentioned, the best way is to use dry film soldermasks like Dynamask 5000 and a relative cheap laminator. The good tutorial how to apply Dynamask is here -> Lötstopp der Film Soldermask the film - YouTube

You can buy Dynamask 5000 here -> Dynamask - Lötstopplaminat 1m kaufen - günstig bei OCTAMEX Dynamask - Lötstopplaminat 1m bestellen - Datenblatt Dynamask - Lötstopplaminat 1m
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Old 1st February 2013, 11:22 PM   #4
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Quote:
Originally Posted by JMFahey View Post
In reality she exposes "everything-but" the pins pads, which are covered by an opaque mask.
Okay, so basically, paint the entire board, cover the pins/pads, then expose everything but the pins/pads to UV. Then the developer will take off the soldermask from the pinds/pad because it hasn't be exposed to UV light?

Does this mean that the product they used was a UV curable solder mask such as this?

New 100g PCB UV Curable Solder Mask Repairing Paint Blue Green | eBay

Also, after UV curing what would I use to remove the solder resist from the pads?
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Old 2nd February 2013, 01:42 AM   #5
JMFahey is offline JMFahey  Argentina
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Quote:
Originally Posted by Fusion916 View Post
Okay, so basically, paint the entire board, cover the pins/pads, then expose everything but the pins/pads to UV. Then the developer will take off the soldermask from the pinds/pad because it hasn't be exposed to UV light?
Yes.
Quote:
Does this mean that the product they used was a UV curable solder mask such as this?
A *similar* one.
Quote:
Also, after UV curing what would I use to remove the solder resist from the pads?
It depends on the product.
The rolled on type used water + a white dust, maybe it was a weak alkali solution as noted.
The Ebay one uses mineral solvents or gasoline.
The classic silkscreen type emulsions I would have used are water soluble.

If silkscreened (my preeferred method), no solvent is needed, I silkscreen solder resist wherever I want and it cures there.
As I said: lots of options.
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Old 2nd February 2013, 03:00 AM   #6
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would I rely on a YouTube video? Not in this lifetime, nor in the next 1,000 lifetimes.

Would I rely on something from Instructables? Maybe have 60 to 80% confidence.
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Old 2nd February 2013, 07:47 AM   #7
HighTec is offline HighTec  Croatia
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What's wrong with that Youtube video? It perfectly shows which steps a hobbyist (amateur, newbie, whatever) should make in order to apply the dry film soldermask. The professionals also do the same thing but with an expensive equipment. If you wanna buy a $4000 laminator then be my guest.

Click the image to open in full size.
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