Shelf life of solder paste
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From: oparr on 31 May 2010 09:12 I've had some leaded, water soluble solder paste (Kester HM531) for the last 3.5 years. Used it yesterday and it seems to still work like new. IIRC, shelf life was given as the usual six months. What gives?
From: George Jefferson on 31 May 2010 09:46 <oparr(a)hotmail.com> wrote in message news:fb7ee7d2-797d-46f5-840b-70e4d4b0d1cd(a)u7g2000vbq.googlegroups.com... > I've had some leaded, water soluble solder paste (Kester HM531) for > the last 3.5 years. Used it yesterday and it seems to still work like > new. IIRC, shelf life was given as the usual six months. What gives? Generally depends on the environment and use. The main issue is when the thinner dries which happens very slowly. A hotter environment will speed up the process. It's not so much that the paste will become unsuable but that it's quality will generally degrade to a point that it is not usable for high density work. So the real question is "What do you mean by 'work'"?
From: Archimedes' Lever on 31 May 2010 10:51 On Mon, 31 May 2010 06:12:37 -0700 (PDT), "oparr(a)hotmail.com" <oparr(a)hotmail.com> wrote: >I've had some leaded, water soluble solder paste (Kester HM531) for >the last 3.5 years. Used it yesterday and it seems to still work like >new. IIRC, shelf life was given as the usual six months. What gives? Shelf lifes of industrial products are so that any mil contractors that use them use them with correct diligence. With many chemicals, they break down after long time periods. Chip capacitor reels have expiration dates because the end terminations oxidize and they pose solderability issues that are costly to address post assembly. So, there are many reasons why expiry dates are utilized on a product. It depends on the product. Fluxes perform by their de-oxidation capacity as it relates to metallic surfaces. It allows the solder to achieve covalent bonds where possible. There can also be viscosity or specific gravity issues if it is used as a foaming flux for a foam fluxer on a soldering machine, etc. So if it still performs fine, and cleans fine, there is likely nothing wrong with it at all. If you are ISO certified, there should be an issue imposed by your quality assurance wording or the like, but nothing *real* is wrong with using it.
From: oparr on 31 May 2010 12:40 > Generally depends on the environment and use. The main issue is when the > thinner dries which happens very slowly. A hotter environment will speed up > the process. Originally, I had something called Amtech Syntech (leaded but not water soluble). Still have the jar....Manufactured date was 1/06 and expiry date was 1/07. Well, it became useless (hard, no tack)in about 8 months prompting me to get the Kester in 9/06. Didn't expect much better in terms of life expectancy so I'm a bit surprised that it is not only still useful but performance seems to be on par with when it was new. Both were refrigerated and handled similarly. > So the real question is "What do you mean by 'work'"? Finest pitch I'm using is .8mm, the tack is still there and it releases from the stencil just fine. Also, I dislodged a 0605 cap while "hot air popping" a defective chip yesterday. All it took was a toothpick to bead the cleaned 0605 pads with the paste and replace the cap. It still works for me. On May 31, 9:46 am, "George Jefferson" <phreon...(a)gmail.com> wrote: >
From: oparr on 31 May 2010 12:48
>So if it still performs fine, and cleans fine, there is likely nothing >wrong with it at all. Hence my surprise given a shelf life of only six months. Not certain whether the brand or the type of solder (leaded, water soluble) is a major factor. On May 31, 10:51 am, Archimedes' Lever <OneBigLe...(a)InfiniteSeries.Org> wrote: > |