Description

This is the part of my big project IOTON MICRIO (Raspberry PI based Programmable Logic Controller for home and industrial automation).

I'm rarely doing things for fun, mostly I'm doing useful things, and have fun from it).

This article is about how to save money if you have small qty production of different design PCBs.

Totally I saved 1150USD for 12 PCBs.

Details

Small calculation

For my project I need the stencils for 12 PCBs (10 for the top side, 2 for both sides)

Let's calculate how much it will cost. 470mm*370mm stencil with valid area 290mm*190*mm with frame and electropolish will cost itself 16.11USD but it's weight is 1.5kg and shipping cost for it is 47.90USD for Singapore EMS.

So 1 stencil with delivery will cost 64USD. For 12 boards it will cost 768USD.

To print paste on the PCB I need a printing machine. Useful machine I found on Aliexpress costs 462USD (with delivery).

So totally for stencils and printing tool I need to pay 1230USD.

In my country median wage for an engineer is about 30000RUR (500USD) monthly.

Lets start to save some money!

The smart solution is to merge all PCB gerber files in one big gerber file. I can do it with the software for PCB preproduction (like CAM350) or find free software (it's exists!). One PCB gerber looks like this:

Merged PCB gerbers for 12 PCBs:

If you wondered why 14 PCBs instead 12, my answer is - additional 2 PCBs is the bottom side.

Really I need only 1 gerber layer for stencil - top paste (.GTP), but board outline layer (typically any mechanical layer or keepout layer) will be useful when you start doing solder paste printer.

So I put 12 PCBs gerbers on one stencil, and now it will cost 49.33USD with electroploishing and shipping (w/o frame). I don't need frame for solder paste printing. Multi board stencil looks like this:

At this stage I saved 768USD - 49USD = 719USD!

This is a lot of money! But let's go further!

Solder paste printing tool.

For the quality solder paste printing I need a precise stencil positioning for each board. You can see PCB height and X/Y adjustment mechanism on any good solder paste printing tool.

But my idea is different!

My idea is about positioning stencil once for all PCBs right away, independent of size and shape. Look what I'm done.

Something about materials and tools I used:

4mm acrylic glass 550mm*450mm (9USD)
M4 thread taper
Drill bits (3.3mm, 4.2mm, 8mm)
Aluminum profile 20mm*20*mm*230mm (1USD)
Milling service (15USD)

At first I prepared the drawings for acrylic glass milling. I have board shape gerber file. It looks like this:

I did some minor changes:

And it's ready for milling. This is milling result:

Groove in order to take out the board.
Hole to place PCB with the components, soldered on top side and print solder paste on bottom side.
Endmill has some radius.

With placed PCBs:

It's time to make a stencil holder.

I placed stencil as well as possible to match holes with soldering plates, and scribes stencil contour with knife.

After that I prepared a holder(20mm*20mm alu profile). I drilled 4mm holes for the fixing bolts, and 10mm holes for the bolts cups.

For fix this thing I drilled holes and cuts thread in acrylic...

Discussions

Jayken wrote 11/02/2019 at 03:05

I like your ideas and I find your point of view enlightening and interesting.

Are you sure? yes | no

Andrey V wrote 09/03/2019 at 07:09

Yes, I found it. But on 100x100mm stencil I will have only 10x10mm of valid printing area.

Are you sure? yes | no

Vitaly wrote 09/03/2019 at 08:20

Could you explain why? There are no jlcpcb limits about mandatory borders. Usually 10mm on each side will be enough for manual use.

Are you sure? yes | no

Andrey V wrote 09/03/2019 at 09:16

Because, as I can see all of the stencils have around 90mm free space around the printing area. It's for the mounting in printing machine, as I understand. Anyway, I think reasonable free space must be more than 50mm (based on my own experience. Also, I found the stenicil cut service from the jlcpcb, it is possible to save some money with it but, not so much as I saved.

Are you sure? yes | no

Vitaly wrote 09/03/2019 at 09:32

IMO you try to compete options, which can exist in parallel. I don't mean your work is wrong, i mean situation is less dramatic when you know about size customization. And that's compatible with your method to hold PCB-s and stencil.

Are you sure? yes | no

Andrey V wrote 09/03/2019 at 09:58

Yes, as I wrote before it is possible to save some money with the smaller stencils. But whole price for all equipment stays high. You can also look, how this technology work IRL here: https://hackaday.io/project/167083-smd-pcb-assy-fast-and-furious

Are you sure? yes | no

Vitaly wrote 09/03/2019 at 15:20

To be honest, i have a bit different use case. You need to assemble a lot of PCB. I need to assemble only 1-2 of one-time prototypes and can't wait other boards to panellize, So, instead of acrylic template i place additional PCB-s from each side, pinned with sticky tape. And use the same sticky tape to pin stencil.

Today received 110*110mm stencil - can confirm jlcpcb has no limits about borders. You can make stencil as small as you wish, according to your preferences about borders. For one-time use 10$ is very attractive price. Of cause, this job can be done with good dispenser, but,,, my one is not ready yet :).

Anyway, i have not seen before your approach about positioning via template and aluminium strap. That's certainly useful knowledge. Thank you for share your experience.

Are you sure? yes | no

Vitaly wrote 09/03/2019 at 07:01

FYI, jlcpcb has option to define custom stencil size. 100*100mm peace will weight ~ 100g. If you do PCB order, such stencil will add 10$ only in total. Without electropolish (i don't know if it's needed or not).

Are you sure? yes | no

Jayken wrote 11/02/2019 at 03:12

Vitaly!

Your micro heat plate for soldering small pcbs is awesome!

Are you sure? yes | no

Save money on stencils and printing.

Description

Details

Small calculation

Lets start to save some money!

Solder paste printing tool.

Discussions

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Just one more thing

Description

Details

Small calculation

Lets start to save some money!

Solder paste printing tool.

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Discussions

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JLCPCB SMT Assembly Service-Complete Guide

My Full Review and Experience with PCBWay

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