Author Topic: Recommendation for a stencil frame and a squeege  (Read 985 times)

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Offline peter-h

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Recommendation for a stencil frame and a squeege
« on: June 16, 2021, 11:38:03 am »
I need to assemble a panel about 15x20cm. Not often, maybe 10 a year. But it wants to be something which is not totally awful.

I tend to use JLCPCB for the stencils, which last time came in at some huge size (roughly A3) and I had to cut them down.

I see loads of these things for sale, at all different prices. For example Olimex in Germany sell a stencil holder for €950:
https://www.olimex.com/Products/Tools/StencilPrinters/
and at that price it ought to be gold plated! But their squeeges are reasonably priced. Olimex don't sell to the UK under €200...

Then I see some on Ebay where even the most expensive are 1/5 of the Olimex price, but obviously these will be chinese and some/most will be junk; the £80 ones are visibly crap
https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2334524.m570.l1313&_nkw=solder+paste+printer&_sacat=0&LH_TitleDesc=0&_odkw=stencil+holder&_osacat=0
Also all the Ebay ones I can see need framed stencils.

My boards are double sided so I need a means of supporting them underneath while printing the topside.

I use a hot air gun to reflow the solder.

Most of the time (a day or so) is spent placing the components.

Any suggestions much appreciated.



« Last Edit: June 16, 2021, 02:55:54 pm by peter-h »
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Offline jmelson

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Re: Recommendation for a stencil frame and a squeege
« Reply #1 on: June 16, 2021, 03:41:06 pm »
I use PCBway, and their stencils also are pretty big.  Way bigger than the board.  But, I had a plate with notched bars for the board to sit in, and was able to rig a hinge to it and clamp the stencil frame to the the hinge with C clamps.
Before that, I made my own stencils out of 0.003" brass shim stock, and those were made to be just about 50 mm bigger than the board.  I used masking tape as the hinge.  So, an unframed stencil can work fine, expecially with less than cutting-edge lead pitch on components.

I'm not sure the commercial stencil holders are any better than the thing I made up myself.

As for a squeegee, I use a piece of 0.025" thick brass shim material.  It is visible to the left in the second picture.  I also have a shower tile squeegee from Ikea that works, but is harder to clean.

Jon
« Last Edit: June 16, 2021, 03:44:15 pm by jmelson »
 

Offline phil from seattle

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Re: Recommendation for a stencil frame and a squeege
« Reply #2 on: June 16, 2021, 07:07:54 pm »
For what it's worth, JLCPCB lets you change the size of the stencil.  Not only that, if you reduce the size of the stencil by a relatively small amount, it drops the shipping cost quite a bit.
 

Offline Mangozac

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Re: Recommendation for a stencil frame and a squeege
« Reply #3 on: June 16, 2021, 09:44:51 pm »
I'm not sure the commercial stencil holders are any better than the thing I made up myself.
Yeah I don't think it's any worse (and possibly better) than our standard Chinese stencil holder. We have it purely for prototyping and backup if our automatic printer were to fail.

For what it's worth, JLCPCB lets you change the size of the stencil.  Not only that, if you reduce the size of the stencil by a relatively small amount, it drops the shipping cost quite a bit.
Indeed, there's really no reason not to order a stencil with your prototypes these days when you can reduce the stencil size down so it has no impact on freight cost.
 

Offline 48X24X48X

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Re: Recommendation for a stencil frame and a squeege
« Reply #4 on: June 17, 2021, 06:01:29 am »
I would recommend using a framed stencil. It provides stability and flatness on the stencil. I don't use any stencil printer and only lay the stencil on top of the PCB. Have been doing this for more than 40K of PCB down to 0.4mm pitch. Only during 1 off prototype I would use the smaller custom size without frame JLCPCB stencil. Before that, even for prototype I would used framed ones but the amount of waste I created prompted me to reserve them for production run only. At times, I would have 50-60 framed stencil that is not being used anymore. For low volume, even those cheapest stencil printer in the links you posted works fine. It all depends on your technique to apply the paste and a good USD5 squeegee.
 

Offline peter-h

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Re: Recommendation for a stencil frame and a squeege
« Reply #5 on: June 17, 2021, 10:35:23 am »
The frustrating thing is that every "cheap" printer I can find is for framed stencils e.g.

https://www.aliexpress.com/wholesale?catId=0&initiative_id=SB_20210617022933&SearchText=solder+paste+stencil+printer+

Even the most expensive there, say USD 600, are for framed stencils only.

The cheapest frameless printer I can find is that €950 SD-240 one posted above (which is sold by various firms although Olimex seem to be the cheapest).

For production, stencils are always framed, but then I don't use JLCPCB for production of anything; the company has basically no "communication capability" (ok; that's a general issue with China; one ends up using the firms which have somebody who speaks English) so you never quite know what will come in the post. Production stencils we get made from panel gerber by the assembly outfit, down the road from us.

I missed this previous thread - same sort of debate :)

https://www.eevblog.com/forum/manufacture/stencil-printers-what-to-buy/25/

There is one frameless printer from china:
https://www.aliexpress.com/i/4000124287041.html
but reportedly the company won't ship to the UK.

Now looking for a reflow oven. Never knew how cheap they are! It looks like the T962 is what everybody is selling, and Aliexpress shows them at a wide range of prices.
« Last Edit: June 17, 2021, 11:05:14 am by peter-h »
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Offline fcb

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Re: Recommendation for a stencil frame and a squeege
« Reply #6 on: June 17, 2021, 12:56:15 pm »
If you're doing 10 per year only (same advice if you were doing 10 per week) - just use an unframed stencil, piece of plywood, some 2" parcel tape and some old PCB's.
Takes less than 5 minutes to set-up. Hell, even if you don't have the plywood - you can do it on a desk.

I'm tempted to do a guerilla video of it - perhaps someone has done one already on YT.

As for the reflow - buy a (toaster) oven, if you've got a K type thermometer then great, else just use a torch/flashlight and watch the board - most ovens have are slow enough to work well.  Just wait for the solder paste to change state and add 60 seconds, then switch-off and crack the door so it doesn't cool at >4C per second.
https://electron.plus Power Analysers, VI Signature Testers, Voltage References, Picoammeters, Curve Tracers.
 

Offline peter-h

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Re: Recommendation for a stencil frame and a squeege
« Reply #7 on: June 17, 2021, 02:04:02 pm »
I have done a few jobs with just the stencil, as you suggest, and with a "fixture" and some tape, it works ok.

But for 10/week, not so sure. Still, the hand assembly of the components does dominate the total time, but it is hard to get pasting consistency if the stencil is not properly stretched.

And reflow with a hot air gun (I have a WEP 858D which is very good) is ok for discretes but much less good for big chips on which you really need to heat up the whole chip at the same time to make it "sit down".

I thought the temp profile is important on the way down too; +300C or whatever for 5 mins won't do some bits much good. Especially some connectors.

Somebody is selling an upgrade for the T962: https://www.ebay.co.uk/itm/192675772419
The oven itself is cheap: https://www.ebay.co.uk/itm/123687959494

Just bought these two so will report :)
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Offline fcb

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Re: Recommendation for a stencil frame and a squeege
« Reply #8 on: June 17, 2021, 02:15:53 pm »
300oC :scared:

Typical solder paste we use melts around 217oC - we don't take it much beyond 240-250oC normally.
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Online jpanhalt

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Re: Recommendation for a stencil frame and a squeege
« Reply #9 on: June 17, 2021, 02:25:52 pm »
I am sure you know the T-962 has the smaller tray.  It is what I use.  I also updated with the United Engineering free firmware and added the Maxim sensor in parasitic mode.  Very easy.  For calibration and adjustment, I used a couple of small TC's inserted through the bottom (tray closed), set close to the oven TC's, and a portable meter.

BTW, I like the tool plate you used.  Mine is smaller and was only about $35 from a US small shop (ebay).  The hold-downs were machined at home.  My real mill is in storage, so I had to make do with hat washers rather than the nice rabbets. I just use tape on the upper hold-down.
« Last Edit: June 17, 2021, 02:27:36 pm by jpanhalt »
 
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Offline peter-h

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Offline peter-h

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Re: Recommendation for a stencil frame and a squeege
« Reply #11 on: June 22, 2021, 06:46:09 pm »
I've ordered the SD240 (from Olimex; the UK disti wanted a load more £££) and will report on how it works.

Got the T962 reflow oven also. Needs some mods ;)
https://www.eevblog.com/forum/manufacture/t962-reflow-oven-233972/50/
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Offline cgroen

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Re: Recommendation for a stencil frame and a squeege
« Reply #12 on: June 22, 2021, 06:53:27 pm »
Peter,
I have the SD-360, the same as yours, just larger and with parallel lift of the stencil.
https://spide-smt.nl/portfolio-item/sd360-u/

The build quality, adjustment possibilities etc are very nice.
I use (frameless) stencils from JLC in it
« Last Edit: June 22, 2021, 06:55:00 pm by cgroen »
 

Offline deanclaxton

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Re: Recommendation for a stencil frame and a squeege
« Reply #13 on: June 22, 2021, 09:52:30 pm »
Peter,
I have the SD-360, the same as yours, just larger and with parallel lift of the stencil.
https://spide-smt.nl/portfolio-item/sd360-u/

The build quality, adjustment possibilities etc are very nice.
I use (frameless) stencils from JLC in it

That looks great! Do you find it easy to tension the stencil, and the magnetic pcb mounts work well? I can't see in the manual where it specifies the tooling hole size for the pcb holders - do they come with a few different sizes or do they have one that can position a board by the corners?

EDIT : From photos it looks like the magnetic PCB holders simply locate the PCB by the board edge - no tooling holes required. Nice. Plus you get a couple of support ones to position under large boards to limit deflection when applying paste.

Neoden vs Spide - Spide ones look more flexible with the PCB mounting. Currently I'm using a block of MDF, a number of pieces of blank PCB boards taped down to hold the actual board in position, and a stencil taped at the top edge. Works, but a parallel lift stencil printer would likely get better results especially on stencil removal.
« Last Edit: June 23, 2021, 12:51:08 am by deanclaxton »
 

Offline cgroen

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Re: Recommendation for a stencil frame and a squeege
« Reply #14 on: June 23, 2021, 05:32:58 am »
Peter,
I have the SD-360, the same as yours, just larger and with parallel lift of the stencil.
https://spide-smt.nl/portfolio-item/sd360-u/

The build quality, adjustment possibilities etc are very nice.
I use (frameless) stencils from JLC in it

That looks great! Do you find it easy to tension the stencil, and the magnetic pcb mounts work well? I can't see in the manual where it specifies the tooling hole size for the pcb holders - do they come with a few different sizes or do they have one that can position a board by the corners?

EDIT : From photos it looks like the magnetic PCB holders simply locate the PCB by the board edge - no tooling holes required. Nice. Plus you get a couple of support ones to position under large boards to limit deflection when applying paste.

Neoden vs Spide - Spide ones look more flexible with the PCB mounting. Currently I'm using a block of MDF, a number of pieces of blank PCB boards taped down to hold the actual board in position, and a stencil taped at the top edge. Works, but a parallel lift stencil printer would likely get better results especially on stencil removal.

Yes, the tensioning and adjustment (X,Y) of the stencil is very easy!
And you are correct, the magnetic bases sits on the edge of the board and they are very "magnetic", they will NOT move unless you apply a LOT of force on them!
 

Offline Jemma.zhang

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Re: Recommendation for a stencil frame and a squeege
« Reply #15 on: June 29, 2021, 04:01:28 am »
I think our company's stencil printer may match your demands.This is the link:https://youtu.be/4fAhuh5dBnc:How to use Tronstol TP3040.
We use positioning beads and positioning posts to fix the PCB board, which can meet your double-sided board needs. Its fixing method is very simple.
We also need framed stencils.
And you cost one day to place the components,why don't think to buy one PNP(Tronstol 3V) and mini-reflow oven(Tronstol MR30) to save your time.



 


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