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February 2001

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Subject:
From:
Brian Ellis <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 23 Feb 2001 16:22:38 +0200
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text/plain (102 lines)
I've said this before and I'll say it again: it ain't temperature that
melts solder, it is heat. You have to pump enough heat (energy, e.g.
calories, joules, watts, horsepower, BTUs etc.) into the parts to be
joined to raise them to above the MP (temp, °C, °R, °F, K) of the
solder. In order to do this as quickly as possible, you need sufficient
thermal mass in the soldering iron bit, i.e., it should be as chunky as
possible as close to the joint as possible, consistent with the
mechanical constraints. If you have a long, thin, conical bit, you have
little thermal mass and you compensate for this by raising its
temperature, so that what little heat that is available is sufficient to
raise the temperature of the parts to above the MP, and the bit cools
accordingly. This ain't good practice, 'cos you can't control the
process. Damn it all, it's simple bloody physics.

Brian

"Busko, Wolfgang" wrote:
>
> Hi Alejandro,
> if you have 400°C at the tip thatīs to much. The risk of damaging parts and
> boards is quite high and if my memory is right the Pb starts to evaporate in
> this temperature range with all the hazards for the operators.
> Consider what you have for temperatures in your wave and your reflow.
>
> I know itīs hard to maintain the temperature during the handsoldering with
> certain equipment thatīs not capable of delivering enough energy in time to
> the tip to encounter the loss that you have due to heating the joint and
> itīs surrounding and itīs widely seen that operators work with higher temps
> to get the job done.
>
> A better way is to use different tips (soldering irons) for different
> joints, using one small tip for everything just doesnīt work. We have at
> least three different sets at the reworkplace with additional hot air device
> for preheating  the units so that thereīs no need to go to high in
> temperature.
> There are other systems available with faster energy transport to the tip
> and easy change of tips ( in seconds ) for different tasks.
>
> Keep things under control and you also might measure your temp. at the tip
> and how it behaves during soldering to see what you need.
> Preheating is often the answer to many problems.
>
> Good luck
>
> Wolfgang
>
> -----Ursprüngliche Nachricht-----
> Von: Becerra Alejandro [mailto:[log in to unmask]]
> Gesendet am: Donnerstag, 22. Februar 2001 00:11
> An: [log in to unmask]
> Betreff: [TN] Temperatures for Rework operation
>
> Hello to All,
>
> I am interested in the optimum temperature for the soldering iron used in
> rework operations.
> At this moment we use 750F (Aprox. 400C) in the soldering irons for the
> touch up operation (Rework operation in line for wave soldering).
> Is it correct this temperature or do we use a lower temperature?
>
> Thanks in advance
>
> Alejandro Becerra
> Quality Assurance
> Phone (915) 841-8439, Fax (915) 841-8401
> [log in to unmask]
>
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