Re: Reducing soldering iron heat
- From: Jeff Liebermann <jeffl@xxxxxxxxxxxxxxxxxxxxxx>
- Date: Mon, 22 May 2006 09:26:55 -0700
"Dave D" <dave-d@xxxxxxxxxx> hath wroth:
If it's not a surface mount device, you could
always clip something to the legs to act as a heat shunt if the heat worries
you.
The son of a friend did a senior project in college modelling and
testing such a heat sink. His theory was that if you removed heat
from the joint by attaching a thermal radiator such as a "protection"
clip, the total amount of heat (BTU's) required to solder the
connection would increase sufficiently to burn the circuit board. I
believe he proved his point, but I didn't read the report. I can see
his point. In the bad old daze of long xsistor leads, a clip placed
near the component would not remove that much heat. However, the same
clip adjacent to the joint would radiate quite a bit of heat away from
the joint requiring that the soldering iron remain on the joint
longer. However, at this point, the discussion is academic as I
rarely see anything resembling an accessible and exposed xsistor lead
long enough to attach a clip.
It is a common misconception that a low powered iron is required for circuit
work- it isn't. In fact, low powered irons can sometimes do more damage than
high powered irons in some cases, for example if the iron is underpowered
the user may keep it on the joint for too long and the sustained heat can
cause component damage and lifted PCB pads.
Agreed. I use a temp controlled 700F soldering iron with a rather
large tip. I work as fast as possible. Tinning the joint with some
fresh solder is often a big help. If you use a low temperature iron
or a very fine tip, the heat affected zone on the board is much larger
than if you use hot iron and big tip.
I have had to use all sorts of irons in emergency situations, from 12 watt
to 100 watt, and prefer a hot iron over a cooler one every time.
Agreed. However, it's not really the wattage of the iron that's
important. Wattage ratings set the upper temperature limit of the
iron if it's not temperature controlled. The size of the tip is very
important. If you use a very fine precision pointed tip, the amount
of heat that can be transfered is very small. There just isn't enough
surface area to do a proper job. Fine tips are required for SMT
components, where a larger tip would hit adjacent parts or pins, but
for where there's room, a big tip works better.
I guess I should mumble something about what I consider a suitable
tip. Forget about the ones that come to a sharp point. A Weller PTA7
with a 0.062 screwdriver tip is good for most everything I do. I have
a collection of other sizes specialized soldering, but the generic
PTA7 works for everything except the really big jobs (solder lugs) and
the really fine work (SMT).
If you're in the market for a soldering station, I suggest one of the
various Weller products that has some form of tip temperature control.
One of these:
http://www.cooperhandtools.com/brands/weller/index.cfm?model_list=1&att_id=WEL003&att1=Soldering%20Stations&att2=Industrial%20Soldering%20Stations
should work. I have a pile of WTCPT stations (60 watts), which I
bought surplus, that work well. Don't bother with the non-temperature
controlled irons.
--
Jeff Liebermann jeffl@xxxxxxxxxxxxxxxxxxxxxx
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
.
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