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phonoplug1
60 posts
Frequent Visitor
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05-09-2009 22:06
Hi,
Just found out something useful - hopefully if will help someone else out there too!
I buy solder paste in 500g tubs, like most paste, this has a 'use by' date on it, generally around 6 months from purchase. I keep it in the fridge as recommended. At it nears the use by date it gets thicker and thicker, making it difficult to use in syringes/with stencils. I found that adding a few drops of IPA to it (Iso Propyl Alcohol) and mixing well, brings it back to a usable viscosity again. I have done this several times to the same paste as it dries out again and it still solders just as well as originally.
Oh, one other bit of advice, don't buy solder paste in syringes! My experience is that its not good. The flux separates from the solder granules and by the time you get half way through, it becomes near impossible to squeeze any more out. Better to buy a tub and fill some very small (2cc) syringes so you can apply more force to squeeze it out.
Hope thats useful to someone! If needs be I can look up the exact type of solder paste I'm using in case IPA doesn't work with other brands.
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BigNiko
1 post
Popping In
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17-12-2009 18:12
I use solder paste in syringes and have suffered the same separation problems. Some brands are better than others and some syringes are better than others. A rounded bottom end with a domed plunger and smooth plastic taper tips seemed to minimise it most, stainless needle tips are the worst. This was all with leaded solder. If you look at some of the lumps under a microscope it appears that the solder particles have sintered into a sponge like structure due to the forces used to expel the paste. I use pulsed compressed air and the paste can get quite warm in use.
The good news is that leadfree pastes don't seem to suffer from this anywhere near as much, if at all, and can be squeezed through 0.013" or 0.010" stainless needles with abandon.
The main thing that wears out as the use by date of solder paste is passed is flux activity. If you can get some IPA based wave solder flux, synthetic is preferable to rosin as it leaves no additional residue, try using it to thin out your stiff paste. It may improve the soldering. For those dispensing from syringes moisten the leads of fine lead ICs with it reinvigorate the flux of out of date paste and improve the soldering.
Nik
Post edited by BigNiko
on 18-12-2009 23:59
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kypros
9 posts
Popping In
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25-02-2010 09:51
I tried thinner and does not work satisfactorily.
I will try IPA as you stated.
Thanks for the tip.
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phonoplug1
60 posts
Frequent Visitor
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26-02-2010 16:48
Another point:
Having thinned out my paste several times (which works ok) I find that the solder is begining to loose its 'stickiness', even though its still thinning ok. Not necessarily a problem but it means you need to be even more careful with loaded boards before they have been baked, and also it gets more difficult to make the smaller components stick to the board and not your tweezers!
So, this time I have added some flux. I have used Weller part number 005 13 831 99, bought from Farnell for just over a tenner (code 157-2843). I choose this one as the datasheet states that it contains Iso Propyl Alcohol (IPA) which I now know works ok with the paste. Thats helped, and it also seems to have helped in leaving a really good shine on the reflowed solder, even when its lead free.
I guess probably not a good idea to only ever add flux (and not IPA) as when the paste dries out as it looses the solvent, you could end up with over fluxed paste. Only a guess though, I'm no expert!
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KyleA
2 posts
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23-05-2012 13:59
You can use this tool to create the stained glass creation for your window or lamp panels. The iron can also be used for jewelry making or repair.From these early developments, jewellery design became a big industry mixed with art and other areas of knowledge and expertise.
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