PCB Silk screening with nylon mesh size possible?

Thread Starter

Joyrider

Joined Apr 29, 2013
9
I would like to use PCB UV-Silk screening like I've seen in this video:
PCB prototyping with UV solder-mask.

In this thread I've read that panty hose, doubled could be used.
Build a screen:
Take 2x2x18 lumber and make a square. Be sure to use 45 degree cuts to put the four pieces together. Get some decent porous fabric. Even panty hose, doubled over, will work. The thing you cant skimp on is the emulsion. Buy a $20 tub of silk screening emultion, (it will last MONTHS) You smear the emulsion on both sides of the screen in a room with a yellow safe light.
I've found this "Food grade nylon mesh" available in 20mesh-500mesh that I want to use for it instead of the doubled panty hose.
Anyone experience this?
How fine and high does it have to be that the UV-Silk can flow well for a nice result?
 

KeithWalker

Joined Jul 10, 2017
1,789
I would like to use PCB UV-Silk screening like I've seen in this video:
PCB prototyping with UV solder-mask.
How fine and high does it have to be that the UV-Silk can flow well for a nice result?
It all depends on the resolution you need. I would suggest that you experiment with the finest mesh you can get, and with different resists to see if it is satisfactory for your needs.
 

Thread Starter

Joyrider

Joined Apr 29, 2013
9
Thanks for the reply,
I've already this UV-silk resist and would like to know what I can expect for the mesh size to be.

When using the resist with a coarse 20 mesh (830Micron) the pcb will get more resit on it then
when using the resist with a very fine 500 mesh (25Micron).
When will the resist flow into an even surface, coarse or fine mesh?
 

KeithWalker

Joined Jul 10, 2017
1,789
Thanks for the reply,
I've already this UV-silk resist and would like to know what I can expect for the mesh size to be.

When using the resist with a coarse 20 mesh (830Micron) the pcb will get more resit on it then
when using the resist with a very fine 500 mesh (25Micron).
When will the resist flow into an even surface, coarse or fine mesh?
The flow will depend on the viscosity of the resist you use. For finer mesh you need a more fluid resist.
 

Thread Starter

Joyrider

Joined Apr 29, 2013
9
@MrSalts,
Thanks for the site.
The site mentiones common use in a table with ink-types and substrate-types where UV-silk resist and PCB are not shown.
Guide lines:
  • 160 Mesh - Our most popular mesh count. Works well with a wide variety of ink types and substrates.
  • 200-230 Mesh - Most commonly used for high detail artwork. Also great for printing with water based inks on wood or paper.
  • 280-305 Mesh - Used for super fine detail artwork, half tones, CMYK process printing, as well as solvent and water base inks.

Although a pcb is a super fine detail artwork in copper and drilling but the UV-silk resist is just a wide surface to be painted.
So maybe the 160 Mesh should be used?

@KeithWalker,
Does that also mean that the more fluid resist can also work with the coarse mesh?
If so then coarse mesh is more common to use then fine mesh?
 

MrSalts

Joined Apr 2, 2020
286
Just use Substrate type = "Plastic & Metal". For standard size 0.030" and bigger text, you'll have 10 threads per letter at 300 thread count. And about 13 threads per letter height at 400 thread count. Ideally, you'll want about 15 to 20 threads per letter for good resolution and 10 to 14 threads per letter for "I'm pretty sure it says..." resolution and under 8 for "i think it's an F or a P and the 'c' looks like an 'o' and the...." resolution.
 

KeithWalker

Joined Jul 10, 2017
1,789
@MrSalts,
Thanks for the site.
The site mentiones common use in a table with ink-types and substrate-types where UV-silk resist and PCB are not shown.
Guide lines:
  • 160 Mesh - Our most popular mesh count. Works well with a wide variety of ink types and substrates.
  • 200-230 Mesh - Most commonly used for high detail artwork. Also great for printing with water based inks on wood or paper.
  • 280-305 Mesh - Used for super fine detail artwork, half tones, CMYK process printing, as well as solvent and water base inks.

Although a pcb is a super fine detail artwork in copper and drilling but the UV-silk resist is just a wide surface to be painted.
So maybe the 160 Mesh should be used?

@KeithWalker,
Does that also mean that the more fluid resist can also work with the coarse mesh?
If so then coarse mesh is more common to use then fine mesh?
Yes, but you have to experiment for optimum results. If the resist is too thin it will creep at the edges.
 

MrSalts

Joined Apr 2, 2020
286
Yes, but you have to experiment for optimum results. If the resist is too thin it will creep at the edges.
No doubt, captain. There are about a half-doesn't other things he'll have to experiment with as well. But since this is your second post on this thread hinting at the concept of viscosity (without using the word, viscosity). Just be careful, you can't solve every problem with a viscosity change.
 

KeithWalker

Joined Jul 10, 2017
1,789
No doubt, captain. There are about a half-doesn't other things he'll have to experiment with as well. But since this is your second post on this thread hinting at the concept of viscosity (without using the word, viscosity). Just be careful, you can't solve every problem with a viscosity change.
I agree, but you can solve them all with a bit of experimentation. I designed my first production line silk-screens and printed circuits for a company I worked for in 1969. I have tried many different types of screens and inks and always managed to get very good results. It's much easier now because you have much more choice of well tested off-the-shelf materials.
Nowadays I just use copper with a photo resist and a computer printed mask for the very small quantities I need in my hobbies.
 
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Thread Starter

Joyrider

Joined Apr 29, 2013
9
For me it all comes down to the delivery time (3-5 weeks) of the nylon mesh or outsourced pcb's from China.
* DIY pcb is 1 fabrication day max and outsourced pcb's is (3-5 weeks).
So when working on several projects and multiple proto types/project then it will take too long to outsource.
For mass production with a finalized error-free project then outsourcing is the way.
* For the nylon mesh I will have to order at least 3 mesh dimensions at once to experiment for optimum results.
Otherwise it will take 3x5=15 weeks to proceed with the projects.
Should I then start testing with 200+250+300 for a wide range of mesh?
 

MrSalts

Joined Apr 2, 2020
286
Should I then start testing with 200+250+300 for a wide range of mesh?
I don't know where you order but 3 weeks for $3 shipping is the lowest price and longest time offered by jlcpcb. If you want to pay $25 for shipping, you get the parts in under 10 days.

so, to answer your question, the answer really depends on how you value time, money and the experience (and what else you might be doing with your time or money. Also, how easily are you satisfied? Will an ok result with 250 mesh be enough for you or will you try the others just in case 300 mesh offers a better result? Each person answers differently so only you can decide if you want to keep buying and trying different mesh sizes.
 

anniel747

Joined Oct 18, 2020
825
For me it all comes down to the delivery time (3-5 weeks) of the nylon mesh or outsourced pcb's from China.
* DIY pcb is 1 fabrication day max and outsourced pcb's is (3-5 weeks).
So when working on several projects and multiple proto types/project then it will take too long to outsource.
For mass production with a finalized error-free project then outsourcing is the way.
* For the nylon mesh I will have to order at least 3 mesh dimensions at once to experiment for optimum results.
Otherwise it will take 3x5=15 weeks to proceed with the projects.
Should I then start testing with 200+250+300 for a wide range of mesh?
You could also use an inkjet printer directly on the PCB.
 

KeithWalker

Joined Jul 10, 2017
1,789
A few years ago I developed a new product and wanted to make the best use of my time and investment. I made the first experimental models on double sided prototype circuit board. For the pre-production models I used photoresist covered double sided PC board, using laserjet printed transparencies for masks and a timed fluorescent light for exposure I used hollow copper rivets for feedthroughs. . When everything was well tested and documented, I outsourced the final boards and assembly. The project was completed in minimal time and was very successful,
That is not the only way to do it, but it worked for me, and I didn't get any masking or resist on my clothes!
 

Thread Starter

Joyrider

Joined Apr 29, 2013
9
I don't know where you order but 3 weeks for $3 shipping is the lowest price and longest time offered by jlcpcb. If you want to pay $25 for shipping, you get the parts in under 10 days.
For proto's that's DIY in 1 day versus 3 weeks jlcpcb.
PCB $3 + Shipping €4 + 10 days delivery $25 = $33 for the first proto.
Only 1 PCB needed but 5 delivered.
Would be better to have an option, say 1 proto PCB for $10 total in 7 days versus DIY €5 in 1 day.
After changes/corrections are made proto2 and later proto3 could be ordered in less time and woud be cheaper then jlcpcb is now.

...on double sided prototype circuit board,
...photoresist covered double sided PC board,
...laserjet printed transparencies for masks,t
...timedfluorescent light for exposure.
...hollow copper rivets for feedthroughs.

...I didn't get any masking or resist on my clothes!
That's the methode I use too :cool:
The UV-resist for me is now needed in my proto's because of long term testing in harsh environment, Top overlay for complex component placements and smooth solder paste reflow for ultra small spacings in footprints like QFP, QFN 44-100pins.

Ik will order these 3 mesh types 200+250+300 and try them together.
 

MrSalts

Joined Apr 2, 2020
286
...versus DIY €5 in 1 day.
your calculation is missing a critical cost element - the cost of your free-time. I'm estimating that the many steps you listed takes a few hours. If you're completely bored, and don't know what else to occupy yourself with, $0/hr is ok. But when you have options like playing with your kids, doing an activity with kids, time with significant-other, time with friends or relatives, calling your mother, taking care of your yard, applicable repairs, etc, etc, etc - then it's a good idea to put a price on your "free"-time and, if the economics are right, pay someone else to do the less interesting parts of a hobby.

Also, I found that diy boards and the "done in a day" theory means sloppiness is tolerated. In your example, you plan on three iterations - I take the time to breadboard an idea, double check my design calculations, double check my PCB design - rarely have I needed a second iteration of a board (never a third). The additional boards from a board-house are nice if you want to test a different op amp, faster microcontroller, etc.
 

Thread Starter

Joyrider

Joined Apr 29, 2013
9
All true, except when the project is a last minute delivery.
More proto's are needed also for additions, upgrades, last minute wish list of the customers, parts/footprint change, obsolete parts, etc.
My projects usually have adjustments one time or another resulting in a better product or several types/variants.
 
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