5 Things to Know Before Buying lead-free hasl

Thanks grufti and Jameson -

The only thing that really gives me pause is that chip with a ton of tiny legs that looks like a metal millipede (the "IC3" that grufti refers to?  I'm unfamiliar with SMD nomenclature). Not sure that I could pull that off with a soldering iron. Maybe if I use a stencil and paste and then heat each leg with fine soldering tip?  Any thoughts/recommendations on this are welcome.

I usually like buying new gear, but I'm hesitant to invest in a hot air station. At least right now.  I've mostly sworn off buying cheap "starter" tools b/c I inevitably end up later buying a well-made one and giving the first one away - completely undermining the "economy" of the first purchase. So the purchase would be pricey.

I wonder whether a regular heat gun -- the kind used for stripping paint, etc. -- might work? I have a good one, adjustable from something like 350F to F with low and high fan speeds.  It looks like after-market nozzles are available online that might get me an approximation of a hot air station. Anyone tried that?

Failing that, I will consider getting a hot air station. I've been steadily working on getting my son interested in STEM stuff (fyi - for those with kids or grandkids: watching Battlebots videos got my son hooked on fantasizing about robot designs and the metal carnage he hopes to one day wreak upon competitors -- although the glean in his eye noticeably lessened when I told him that building a similar contraption would require a lot of physics, engineering, math and programming know-how). So maybe a rework station wouldn't go to waste. But I can't see it being all that useful for my diy audio interests - I'm too much of a tweaker/rebuilder and need point to point.

cheers and thanks, Derek

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do not mix Pb solder with the low temp Bismuth-based solders (also there is the different melting point issues, but the alloy that forms is awful). Joint becomes very brittle due to strong intermetallic growth and easy to break with even what I could consider moderate force. For example, with the right (or wrong) mix of solder and a decent grip, I can pull SMD aluminium polymer caps off the board with my bare hands.

I'm pretty sure remember reading a super old IBM article where they investigated this Bi/Pb mix for some temperature sensitive parts in a mainframe, and it was a disaster. Can't find the article now though 

Also from

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If you want to learn more, please visit our website lead-free hasl.

Caution must be used when using tin / bismuth alloys. It is dangerous to mix tin / bismuth with lead containing alloys. Tin, bismuth, and lead can form a very low melting combination that melts around 95 °C. This could potentially lead to solder joint failure due to natural heating of the assembly during use.
 
Tin / bismuth alloys are safe to use in combination with other lead free tin-based alloys. In some cases surface mount assemblies are made with SAC305 on the first side and tin / bismuth on the second side. The low reflow temperature for tin / bismuth minimizes intermetallic growth in the SAC305 solder joints and allows for soldering of thermally sensitive components.

Definitelymix Pb solder with the low temp Bismuth-based solders (also there is the different melting point issues, but the alloy that forms is awful). Joint becomes very brittle due to strong intermetallic growth and easy to break with even what I could consider moderate force. For example, with the right (or wrong) mix of solder and a decent grip, I can pull SMD aluminium polymer caps off the board with my bare hands.I'm pretty sure remember reading a super old IBM article where they investigated this Bi/Pb mix for some temperature sensitive parts in a mainframe, and it was a disaster. Can't find the article now thoughAlso from http://www.surfacemountprocess.com/low-temperature-lead-free-solder-paste.html

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