Rudy's answer ties in with what I know. However, there are important
variations in the behaviour of solvents and the form of the aluminium.
If you take a pure halocarbon and dump in very finely divided amphoteric
metals (esp. the very reactive ones, such as lithium, sodium, potassium,
calcium, magnesium, aluminium and possibly even zinc or iron), the
reaction is spectacular. As Rudy said, for a given molecular structure,
fluorocarbons are the least reactive (ever see a Teflon coated aluminium
frying pan?) followed by chlorocarbons, bromocarbons and iodocarbons, as
the most reactive. But it ain't as simple as that. If they are
perhalocarbons, they tend to be a lot more stable than hydrohalocarbons,
which can be more spectacular, depending on the hydrogen:halogen ratio.
Even more so is when you have an atom or two of oxygen in the molecule
such as halogenated ethers and alcohols.
Of course, if the alu and even magnesium are in a lump (small surface
area) and the solvent is stabilised and buffered, there is no problem.
Brian
Gaugler, Kevin wrote:
> Happy Hump-day Techies,
>
> Sorry this is not really a PCB assembly question but I know someone out
> there will have some insight on this topic. What is the mechanism
> behind the violent reaction between aluminum and halogenated
> fluorocarbons? Does the reaction occur spontaneously at room
> temperature? What conditions are required for the reaction
> to occur (pressure, temperature, etc?)
>
> Any insight would be appreciated.
>
>
>
> Kevin Gaugler
> R&D Manager
> Solder Paste Operations
> EFD, Inc.
>
> www.efdsolder.com
> <mailto:[log in to unmask]>
> phone: (401) 333-3800 x2221
> fax: (401) 333-4954
>
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