Solder paste - Page 1
Forum section: electronics / beginners

author: netdudeuk
author_rank: Frequent Contributor
timestamp: October 09, 2013, 07:26:45 am
content: HiI've been looking at solder paste on eBay and what's described as such doesn't really look like it to me.On the videos I've watched, the paste always looks metallic but the cheap eBay tubes always look yellow. There's always 'flux' in the description and sometimes a mention of 'alloyed' powder but no mention of the composition.Are they of any use for soldering SMDs to boards ?Thanks

author: herctrap
author_rank: Newbie
timestamp: October 09, 2013, 07:32:36 am
content: also can you apply the paste on a pcb without a stencilfor 0805 and tqfp packages?thanks a lot

author: johnnyfp
author_rank: Frequent Contributor
timestamp: October 09, 2013, 07:57:03 am
content: Herctrap, yes for sure you can use paste without a stencil. Makes fine pitch prototypes easy to solder in one go.Netdudeuk, if its yellow then its most likely just flux. Typically solderpaste is grey in colour.

author: netdudeuk
author_rank: Frequent Contributor
timestamp: October 09, 2013, 08:21:10 am
content: Thanks for the reply. I more or less came to the same conclusion because of the yellow but why would it have 'alloyed' powder in there if it was just flux ?

author: Kjelt
author_rank: Super Contributor
timestamp: October 09, 2013, 08:38:32 am
content: There are all kinds of solderpaste, where my experience led me: the ones in the yar are for stencils only, the balls are twice bigger and the paste is to thick to go through ( maybe very big ones).And you have the paste in a syringe which is more expensive but also has smaller balls so it is good for manual application with a syringe.Since these pastes need to be held cool and have limited shelf life of half a year i would not recommend ordering them from ebay but go to a local shop or webshop in your country.Btw the shelf life is for guaranteed production quality, for hobbieist i have it for over a year and still works fine

author: johnnyfp
author_rank: Frequent Contributor
timestamp: October 09, 2013, 08:39:37 am
content: Link the url. Mystery to me.

author: netdudeuk
author_rank: Frequent Contributor
timestamp: October 09, 2013, 08:51:45 am
content: Here's an examplehttp://www.ebay.co.uk/itm/Advanced-Repair-Tool-Solder-Soldering-Paste-10cc-Flux-Grease-RMA-223-RMA-223-New-/300618817133

author: johnnyfp
author_rank: Frequent Contributor
timestamp: October 09, 2013, 08:57:49 am
content: Yeah its just flux.

author: herctrap
author_rank: Newbie
timestamp: October 09, 2013, 08:58:22 am
content: that seem like flux onlynot paste

author: poorchava
author_rank: Super Contributor
timestamp: October 09, 2013, 09:06:02 am
content: Common problem. They use the term 'solder paste' to describe both 'paste that you use for making soldering easier (a.k.a. flux)' or 'paste that contains solder balls'.

author: sleemanj
author_rank: Super Contributor
timestamp: October 09, 2013, 09:25:47 am
content: The most common (cheapest) actual solder paste on eBay is "Best" or sometimes "Mechanic" brand and sold in "50g" pots.Do not necessarily expect to get 50g (net or gross), but that's what's written on the label. Last one I got was like 25g, including the jar (to their credit, they refunded half).If you search eBay for "solder paste 63/37" you'll find it without all the mis-named fluxes.

author: mrflibble
author_rank: Super Contributor
timestamp: October 09, 2013, 09:30:38 am
content: Quote from: netdudeuk on October 09, 2013, 08:51:45 amYeah, that's solder flux. I have the very same one here, complete with highly optimistic "AMTECH" label on it. Somehow I highly doubt it's genuine Amtech, but it works well enough as flux.As for actual solder paste, the Mechanic paste works fine. I usually get it from deal extreme.

author: Orpheus
author_rank: Regular Contributor
timestamp: October 09, 2013, 10:22:23 am
content: Yup I've been getting Mechanic solder paste from deal extreme for years. About to order more.I suggest refrigeration and periodic stirring to keep it in top form to 6mos and beyond. I tried mixing in flux or rosin+isopropanol to "restore" solder paste", which MAY work, but is never as good.

author: netdudeuk
author_rank: Frequent Contributor
timestamp: October 09, 2013, 10:27:18 am
content: I assume that you mean this ?http://dx.com/p/mechanics-soldering-paste-50g-7952?Do you just use something fine to spread it onto the SMD pads ?There's plenty of that stuff on eBay toohttp://www.ebay.co.uk/itm/New-Mechanic-Solder-Soldering-Paste-Welding-Flux-63-37-25-45um-/200941884492?pt=UK_Home_Garden_PowerTools_SM&hash=item2ec911d44c

author: mrflibble
author_rank: Super Contributor
timestamp: October 09, 2013, 10:48:57 am
content: Quote from: netdudeuk on October 09, 2013, 10:27:18 amYup, that's the stuff. I put a small amount in a syringe. You can use a random object with a fine tip to put paste onto pads, but that's a bit annoying in my experience.

author: chibiace
author_rank: Regular Contributor
timestamp: October 09, 2013, 10:53:50 am
content: the dx stuff is nice enough for me. when i do most smd caps and resistors the application doesnt need to be too precise but i do like it when its tacky enough to hold the parts while i use the hot air as to not have them blowing off the mark or spinning around 180 degrees.

author: mrflibble
author_rank: Super Contributor
timestamp: October 09, 2013, 12:14:20 pm
content: Quote from: mrflibble on October 09, 2013, 09:30:38 amROFL! As a followup, I just checked that "AMTECH" flux. On the label:WARNING:May contain lead. This product contains chemicals knomn to the state of Colifomia and other states to canuse cancer,birth defects or other reproductive harn.Consuit MSDS.For industrial use only.Not for resale, unauthorized distribution or personal use.*giggle* Yes, I am sure this product is knomn to the state of Colifomia.Well, at least the "Made in China" seems truthful enough.

author: netdudeuk
author_rank: Frequent Contributor
timestamp: October 15, 2013, 08:17:27 pm
content: Thanks. I'll have a look.

author: peter.mitchell
author_rank: Super Contributor
timestamp: October 16, 2013, 01:25:06 am
content: Quote from: mrflibble on October 09, 2013, 12:14:20 pmI think that warning is pretty commonly copy-pasted, I use a fair bit of flux, and on many of the tubs I have bought have that same warning, spelling mistakes and all.

author: mrflibble
author_rank: Super Contributor
timestamp: October 16, 2013, 04:25:08 pm
content: Really? I guess I should buy more varied flux from China then.So far I only noticed it on the knockoff Amtech flux.