Stencil Printer - Page 1
Forum section: electronics / general

author: l0wside
author_rank: Regular Contributor
timestamp: June 15, 2016, 07:53:02 am
content: Currently, I am printing my paste with Elecrow 120µ stencils on a piece of cardboard with some old PCBs as standoffs. Smallest feature sizes are 0.5mm QFN and 0603. The results are kind of ok, it is not uncommon that I have to wipe re-print the paste due to misalignment or smearing. I do double-sided boards, which complicates things further. Squegee is a metal scraper.Decent manual printers seem to start at around 1500$/EUR, which is out of scope. There seems to be a certain Chinese standard for framed stencils (30x40cm) at ridiculously low prices ($30 at Elecrow w/ electropolishing). There is a number of corresponding printers for these:The cheapest one is this:http://www.ebay.com/itm/Stencil-Screen-Printer-Solder-Paste-T-shirt-Printer-Screen-Printing-Machine-/222033402795Equally cheap:http://www.ebay.com/itm/CYBRES-SP2421-Manual-Stencil-Printer-SMT-Schablonendrucker-/152112655945(has a funny video at).Then, there is NeoDenhttp://www.ebay.com/itm/NeoDen-PCB-Assembly-high-precision-accurate-stencil-solder-printer-PM3040-/182119586650- $500 is more than I was willing to spend, but if it is a decent printer, I might spend the money (provided they do something about the shipping).Any experiences, recommendations, ...?Max

author: ebclr
author_rank: Super Contributor
timestamp: June 15, 2016, 07:58:00 am
content: Take a look on this onehttp://www.aliexpress.com/item/YX3040-High-Precision-Stencil-Printer-SMT-Machine-300-400mm/32340437079.html?spm=2114.01010208.3.189.vOUrGJ&ws_ab_test=searchweb201556_8,searchweb201602_4_10038_10037_10017_507_10032_401_10040,searchweb201603_3&btsid=77a7a9fe-cd04-4313-9bac-2293adafa855

author: l0wside
author_rank: Regular Contributor
timestamp: June 15, 2016, 11:37:11 am
content: Do you have any experience with the part? The seller is quite pushy.Max

author: ar__systems
author_rank: Frequent Contributor
timestamp: June 15, 2016, 05:41:11 pm
content: Ok today I finally tried my tensioning system frame together with this printer:http://www.aliexpress.com/item/45x60cm-Stencil-Printer-SMT-Stencil-Printer-Solder-Paste-Printers-DHL-Free/693764213.html?spm=2114.01010208.3.66.9p7AI8&ws_ab_test=searchweb201556_0,searchweb201602_4_10037_10017_507_10032_401_10040,searchweb201603_3&btsid=b91f82df-b44c-4048-932a-44d8d88c5a91Well not exactly, but smaller model from the same supplier.The result is obviously much better compared to trying to print with just the stencil without frame. The very first attempt was nearly perfect.Now, the printer itself, although it is not marketed as "precision", is very similar in construction to yours and suffers from a a couple of flaws. It is not rigid enough. I can easily sway the frame laterally, by about 0.2mm I think. Not a lot but if I want to have repeatable fine prints I can't have that much of play. Also the bracket that clamps the frame is made of a very thin metal and so it bends when I tighten the screws, and I don't even apply too much force. Your "high precision" is probably going to be exactly the same in that regard.I think I'm going to install a guide pin on the opposite side of the frame to prevent it from moving sideways. Going forward it is a bit of a problem, if I'm going to buy framed stencils, I'll have to drill the guide hole every time. And it will have to be fairly accurate. So that's a difficult technological step.

author: elecman14
author_rank: Unknown
timestamp: June 15, 2016, 08:17:03 pm
content: Quote from: l0wside on June 15, 2016, 07:53:02 amThis one appears to be mostly made out of 80/20 or some knock off version of it. If you wanted to build your own this would be a good material to use. depending on the hinges they use this could be a fairly sturdy (that should lead to reputability) and easy to modify. The parts are fairly availablehttp://www.mcmaster.com/#80-20-compatible-t-slotted-framing.

author: ar__systems
author_rank: Frequent Contributor
timestamp: June 15, 2016, 09:56:22 pm
content: couple more tries with a different paste and I got a perfect result. The first paste was expired and was flowing on its own.But now when I look at this print (this is 0.5mm pitch chip) I see that cross section of the paste is almostrectangularsquare, in other words is as tall as it is wide. I checked the stencil and it is 0.2mm. Should I get a thinner stencil?

author: uncle_bob
author_rank: Unknown
timestamp: June 15, 2016, 11:13:59 pm
content: Quote from: ar__systems on June 15, 2016, 09:56:22 pmHiYes, you probably should. It also is possible that your pads are not big enough, but I'm guessing that is not the issue.Bob

author: janekm
author_rank: Unknown
timestamp: June 16, 2016, 12:05:29 am
content: Quote from: ar__systems on June 15, 2016, 09:56:22 pmYes. 0.12 or 0.1mm thickness are standard when there's 0.5mm pitch QFN involved. Normally the shops do a decent job picking a suitable thickness...Another thing, you should stir up your paste before you use it (there's a special thin "palette knife" for that but I usually use a metal chopstick) until it looks a bit glossy. This warms up the paste and helps with printing (and also of course makes sure the paste is well mixed). Usually for me the paste dries out a bit with age, and I've had decent luck adding a few drops of ethanol (not the correct solvent but it just evaporates away after printing so no harm done). But too much and the paste is ruined.

author: l0wside
author_rank: Regular Contributor
timestamp: June 16, 2016, 08:12:02 am
content: @ar_systems, thank you. Your paste print looks great, even more so for 200µm @0.5mm pitch (which is indeed way too much).I think I´ll go for the printer and will report back when I have it.Max