Stencil for 0402 SMD? Recommended fab house - Page 1
Forum section: electronics / general

author: Mecanix
author_rank: Frequent Contributor
timestamp: August 24, 2020, 04:37:06 am
content: Working on a BLE/RF pcb. Assembly to be carried manually under magnification(and caffeine) therefore, preferably, will need a stencil done between 60 and 80μm in thickness.Q1: Will JLCPCB be able to deliver this? or do I need to look-up for that trillion-dollar fab house to get those prototype pcb and stencil done?Q2: Anyone of you doing/have done 0402 SMD with some good <100μm solder paste using those 'standard' JLCPCB stencils?Q3: Forget the stencil and hand solder 0405?! ps. my enrage-threshold is 0603...Thanks!

author: Bud
author_rank: Super Contributor
timestamp: August 24, 2020, 05:25:23 am
content: How many boards? If only one or a few of them, a syringe with gage 24 needle should do it. You already have a magnifier.

author: Dubbie
author_rank: Unknown
timestamp: August 24, 2020, 05:27:20 am
content: I do 0402 and 0201 all the time with the 100μm stencils that JLC does.I get electropolished. I don't know what the difference is if you don't get that. I've always gotten it.I use T3 size paste.By far the biggest variable for me was my squeegy technique.

author: Mecanix
author_rank: Frequent Contributor
timestamp: August 24, 2020, 06:31:26 am
content: Quote from: Bud on August 24, 2020, 05:25:23 amGood tip on the syringe #24, I'll equip! (Thanks!). I'm after one validation prototype board to begin with. So... e.g. 5 pcb from JLCPCB with its matching stencil, was my initial plan. I do however prospect a role-out of that BLE circuit onto a larger board; the RF tuning, shielding and cert to be outsourced to someone who knows what he/she is doing though(by late autumn, hopefully).Never attempted 0402 let alone seen the footprints and solder masks (accuracy?) that comes out of JLCPCB or PCBWay. Glad to hear @Dubbie is doing them all the time.Quote from: Dubbie on August 24, 2020, 05:27:20 amelectropolished - Something to do with deburing sharp edges if I'm not mistaken, required for micro sized features. Could be wrong...Do we have anyone else other than JLC who does those thin'er stencil that we know of? (in the prototyping pcb mfg arena that is...)

author: Dubbie
author_rank: Unknown
timestamp: August 24, 2020, 09:04:46 am
content: Just a little sample of a board I pasted the other day.It might look a bit crude but that’s because the whole board is only 12mm x 12mmThe two footprints below and to the left of the “D” are 0201 and the rest are mostly 0401.The tiny footprint on the left was a challenging 0.4mm pitch DSBGA only 1.6mm x 0.8 for the whole chip!Still worked fine.

author: SMTech
author_rank: Frequent Contributor
timestamp: August 24, 2020, 09:13:56 am
content: .1mm/4thou is fine for 0402 and 0.4mm pitch, electropolished stencils will have better paste release and a smoother roll/stroke when you squeegee. Leave pasting a board with a syringe to the crazy people.

author: Mecanix
author_rank: Frequent Contributor
timestamp: August 24, 2020, 11:30:37 am
content: Quote from: Dubbie on August 24, 2020, 09:04:46 amToo kind, appreciate the effort in posting this visual, Dubbie. Reassuring to know this can work out for $2. Unbelievable in fact!!!Is it just me or those traces looks enormous lol 12x12, a whole new level right there...On a slightly concerning note; that is a pretty damn thick solder goo, no? I understand it works and that's all what matters for those proto boards, but is it all we have access too? Can we send a few thin sheets of stainless to JLC and have them cut some stencils for =< 0.3mm pins and all that good stuff?In the other preps; I've put an order for both Type 4(20~38) & Type 5(15~30) solder paste jars with some 25ml 'thinner' btl they sell. Gearing up to see what I can achieve with those fat stencils and a cheap home workbench :/Quick questions: (1)What sort of solder mask expansion width you put around those 0.5mm pads? (2) and what is the minimum stroke width we can give to the overlay/silkscreen? Would a 0.05mm width print fine and be readable? (Qs in regards to JLC mfg ofc). Thanks

author: asmi
author_rank: Super Contributor
timestamp: August 24, 2020, 06:34:23 pm
content: I use electropolished framed stencils made by JLCPCB for all kinds of parts, including 0.4 mm pitch QFNs, 0.8+ mm BGAs and tiny stuff like 0201 caps with no problems. But you have to realize that how you print the paste has a huge impact on results you get. Which is why I invested into manual framed stencil printer. For one-offs you probably won't need it, but for any kind of repeatability you will greatly appreciate it.

author: Dubbie
author_rank: Unknown
timestamp: August 24, 2020, 06:42:22 pm
content: Regarding the expansion. I forget what I used on this, but I just followed the manufacturer recommendations in the datasheet. I wouldn’t worry about the fatness of the blobs. Everything flows perfectly.You can see the D and C and + and - on my board silkscreen. They are only just legible, they are the lower limit of what JLC claims to do on their capabilities page. You can see if you went smaller than that it would become unreadable.

author: Mecanix
author_rank: Frequent Contributor
timestamp: August 24, 2020, 07:04:07 pm
content: - Electropolished stencil- Fresh jar of Type 5 goo (I've been recommended to add a drop of thinner in the paste, stir and use a soft silicon rubber edge with medium pressure to avoid edge built-up)- Caffeine abuse- Tweeze-on a total of 13,776,233 miniature 0402 parts and other pitch .5mm with 0.25mm pad width ICs- Bit more caffeine abuse- Gun it @250dCLet's see... here we come JLCPCB. Thanks for all the great tips and encouragement guys, appreciated. Let's hope this miniaturizing thingy doesn't become an addiction, I have a mountain of 1206 and 0805 parts to get rid of before lol I'll report if all blows up (I doubt after seeing Dubbie's 12x12(mm), amazing result)

author: asmi
author_rank: Super Contributor
timestamp: August 24, 2020, 08:32:07 pm
content: Quote from: Mecanix on August 24, 2020, 07:04:07 pmDon't you worry - you will have a large stockpile of reels of 0402s in no time!They are so cheap ($3-6 per 10K reel for most values of resistors, caps are slightly more expensive - up to $20-30 for some values) that I always buy them by the reel, and by now I have racks of these reels. When my non-EE-enlightened friend visited me and he saw all these reels, he thought these reels were with magnetic tape, and his immediate comment was - "am I in the NSA listening post?"Also, if you got the money, invest into stereo-microscope (like AmScope SE400) and a good vacuum pickup tool - this will speed up placement tremendously and will make the process much more comfortable.