Stencils, 3mil or 5mil? - Page 1
Forum section: electronics / projects

author: zapta
author_rank: Super Contributor
timestamp: March 11, 2014, 06:37:23 am
content: OSHStencil is now offering 5mil stencils in addition to the existing 3mil stencil.What are the considerations of choosing the stencil thickens? Should I stick with the 3mil or switch to the 5mil?(if it matters, I am using chipquick SMD291AX10T5 paste, 28 SSOP packages, occasional small boards, and reflowing manually with hot air).

author: JimmyM
author_rank: Regular Contributor
timestamp: March 11, 2014, 12:20:12 pm
content: If what you're using is working, then don't change anything.

author: zapta
author_rank: Super Contributor
timestamp: March 11, 2014, 10:37:40 pm
content: It's look to me a little bit low on the solder but am not sure what is normal.

author: gxti
author_rank: Frequent Contributor
timestamp: March 12, 2014, 01:57:41 am
content: 5mil should be sturdier, which is good because I've had problems with the webbing between pads stretching and even breaking after 10 applications. It will also let me use smaller apertures which means more solid material which makes it even stronger.

author: calexanian
author_rank: Super Contributor
timestamp: March 12, 2014, 02:34:44 am
content: The parts may "Stick" a but better with a thicker stencil but that's kind of subjective. Sometimes too much of a fillet can cause issues... Your mileage can vary!! So long as its flowing and not bridging you are fine. Most of the contact is actually under the pin anyways... It's nice when you have your process down right and every joint looks perfect with just that right amount of fillet and well flowed!

author: johnwill
author_rank: Contributor
timestamp: March 12, 2014, 08:51:25 am
content: Dont you think its bit lower

author: zapta
author_rank: Super Contributor
timestamp: April 05, 2014, 03:32:13 pm
content: I got the 5mil stencil and like it much better. No bridging and the solder points don't look 'starved' anymore.This made me to thin, when device manufacturer specify recommended footprints for their products, do they assume a specific stencil thickness? Is there a standard or convention for stencil thicknesses?

author: methods
author_rank: Newbie
timestamp: December 30, 2020, 01:23:47 am
content: Its been a long time since I have used a printed VuGraph Stencil.Over the last month, I used a stainless for the first time. It came with a nice matched set, worked well. My only gripe was "no visual indicator". ... With clear, you can see that you are getting solder on the underside of the stencil. With metal. . . you have to remember to clean it every time...As for thicknessMy opinion (and I am no pro, but I have made plenty of PCB's in the toaster oven -> hundreds) is that having *less* solder is good if your process is totally dialed. For me, ::* If I am using a funky oven* If I am having to do a bunch of preheat* If I can afford the space (not doing anything super-critical)...I would go with 5mil.More solder is always easier for me to rework than not enough. I rarely get a bridge with solder paste, converging on never. What I do get a lot of is starved out joints.... By starved out...I mean they are no doubt good joints (good electrical connection under the pad) but visual inspection fails for lack of a fillet. I REALLY prefer to be able to visually inspect, see the solder, know I am good. ... Having surface mount connectors pop off is super lame....EhOf course... Panelize as much as you can. If you are rubbing only one small board at a time it wont scale. You will have to clean the underside every time, scrape over and over... meh. Best to run a full panel at a time - so - like 6 boards... something to make it worth your efforts....ehI recently tried out some of that Solder Paste on Digikey that does not have a cold storage requirement. My opinion was that it sucked. I did get the process down (and did punch 4 boards in a row, perfect) ... but it was a long time getting there. My opinion is that Good Solder is not something to skimp on. For rework I use Kester (in 3 sizes) along with real flux pens (not the no-clean). I wash in a giant 99% bath - I do it old school....anywayI use Kester for anything solder brand. Mostly because I have had a good experience with them for 20 years. No idea what the cool kids use, but for this run I bought whatever was leaded in brand Kester and I keep it in a minifridge... ehI use the Yellow tweezer kit that was for sale on Amazon a decade ago. They last forever. My favorite tweezer is the baby blue.... Off track hereAs for scraping pasteI have always found that a credit card did the trick fine. I also use razor blades... but be careful using a blade on non-metal stencil. Metal Stencils (Where I buy them) are a hundred bucks... so... all for getting a cheap clear one for one-off boards. Once you learn to solder paste . . . there is no going back. It is MUCH faster than hand soldering if you get your process down.Process. . .Is what it is all about. BAM, BAM, BAM....OKI am slacking off over here. . . back to ordering my OSH park Stencil. My feedback on OSH is that they have been good in general. When they get backed up. ... eh... I cant use them.... but right now? Pfffttt... I punched a board thru there almost as fast as my usual place. I only select the Super Swift service and I always condense a design down to 2 layers. I try to go only one side, but these days I am having to pack top and bottom (which makes... stenciling... a LOT HARDER... EH HEM>>> so think about that*)... I dont actually know how folks jig for top and bottom stencil. Sure I could figure something out. Jigsaw puzzle of old FR4.Good day to you ladies and gentlemenz.-methods