Reducing soldering iron heat

[[email protected]]

I have a 40W soldering iron; I need to solder a small transistor in a
PCB. I guessing 40 watts is too much heat for that task, so could I add
a incandescent bulb in series with the iron to reduce the heat? If so;
what watt lamp? (40, 60, ect) Thanks

 

[Ross Herbert]

I have a 40W soldering iron; I need to solder a small transistor in a
PCB. I guessing 40 watts is too much heat for that task, so could I add
a incandescent bulb in series with the iron to reduce the heat? If so;
what watt lamp? (40, 60, ect) Thanks

You need to give the make and model of your soldering iron in order to
give a definitive answer.

If your soldering iron heater element is powered from a step-down
transformer you can use the old technique of inserting a power diode
in series with the heater element so that the element receives only
half wave pulses of current. You can arrange for the diode to be
switched in or out of circuit as required.

 

[[email protected]]

As long as the soldering iron is directly hooked up to the AC power and
not step-down transformer powered or not DC powered there are two easy
ways of reducing the soldering iron temp:

1. A cheap incandesent light dimmer (installed in an electrical box)
2. A silicon diode like a 1n4002 in series (will also work with AC
step-down tranfromer powered irons)

electricitym
..
..
..

 

[[email protected]]

As long as the soldering iron is directly hooked up to the AC power and
not step-down transformer powered or not DC powered there are two easy
ways of reducing the soldering iron temp:

1. A cheap incandesent light dimmer (installed in an electrical box)
2. A silicon diode like a 1n4002 in series (will also work with AC
step-down tranfromer powered irons)

electricitym
.
.
.

The diode trick seems to work better than the light bulb series idea I
had before.
It is just a standard cheap iron that plugs directly into AC. Thanks
for the help!

 

[g. beat]

As long as the soldering iron is directly hooked up to the AC power and
not step-down transformer powered or not DC powered there are two easy
ways of reducing the soldering iron temp:

1. A cheap incandesent light dimmer (installed in an electrical box)
2. A silicon diode like a 1n4002 in series (will also work with AC
step-down tranfromer powered irons)

electricitym
.

The light dimmer approach has been featured in ARRL Handbook since 1970s,
when the dimmers first came on the consumer market.
BTW, did you know that the Weller WLC100 solder station is just a 40 watt
stick iron with such an OEM light dimmer?
The Weller WPC300 is the controller without the iron.

Read all about it
http://www.uoguelph.ca/~antoon/circ/wlc100.html

 

[Dave D]

I have a 40W soldering iron; I need to solder a small transistor in a
PCB. I guessing 40 watts is too much heat for that task,

No, 40 watts is fine. The trick is to not keep the iron on the joint too
long, and with a high powered iron it isn't necessary to do so- the joint
can be soldered in a second or two. Transistors are a lot more robust than
many people think- I don't recall ever destroying one by soldering iron
heat, and that includes SMDs. 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.

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.

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.

Dave

 

[Jeff Liebermann]

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/bran...g Stations&att2=Industrial Soldering Stations
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.

 

[ian field]

You need to give the make and model of your soldering iron in order to
give a definitive answer.

If your soldering iron heater element is powered from a step-down
transformer you can use the old technique of inserting a power diode
in series with the heater element so that the element receives only
half wave pulses of current. You can arrange for the diode to be
switched in or out of circuit as required.

Another trick is to use a transformer with secondary taps at various % of
the mains in and wire the secondary antiphase in series with the element to
subtract voltage from the mains, even easier is an old type transformer with
several taps for various mains voltages - then its possible to just use the
primary as an autotransformer.

 

[ian field]

You need to give the make and model of your soldering iron in order to
give a definitive answer.

If your soldering iron heater element is powered from a step-down
transformer you can use the old technique of inserting a power diode
in series with the heater element so that the element receives only
half wave pulses of current. You can arrange for the diode to be
switched in or out of circuit as required.

Another trick is to use a transformer with secondary taps at various % of
the mains in and wire the secondary antiphase in series with the element to
subtract voltage from the mains, even easier is an old type transformer with
several taps for various mains voltages - then its possible to just use the
primary as an autotransformer.

 

[ian field]

You need to give the make and model of your soldering iron in order to
give a definitive answer.

If your soldering iron heater element is powered from a step-down
transformer you can use the old technique of inserting a power diode
in series with the heater element so that the element receives only
half wave pulses of current. You can arrange for the diode to be
switched in or out of circuit as required.

Another trick is to use a transformer with secondary taps at various % of
the mains in and wire the secondary antiphase in series with the element to
subtract voltage from the mains, even easier is an old type transformer with
several taps for various mains voltages - then its possible to just use the
primary as an autotransformer.

 

[sofie]

..... that is 3 tricks if I am counting correctly.
- - - - - -

 

[ian field]

.... that is 3 tricks if I am counting correctly.
- - - - - -

The server's been playing silly buggers all evening, it keeps telling me
"server could not be found" then sends the post 3x all with identical time
stamp!

 

[Jim Yanik]

Another trick is to use a transformer with secondary taps at various %
of the mains in and wire the secondary antiphase in series with the
element to subtract voltage from the mains, even easier is an old type
transformer with several taps for various mains voltages - then its
possible to just use the primary as an autotransformer.

Use an ordinary lamp dimmer;they will handle 100W lamps.

 

[GregS]

Another trick is to use a transformer with secondary taps at various % of
the mains in and wire the secondary antiphase in series with the element to
subtract voltage from the mains, even easier is an old type transformer with
several taps for various mains voltages - then its possible to just use the
primary as an autotransformer.

I've tried em all, including unplugging the iron before it gets too hot!

I bought a cjeap Radio Shack iron for trips, has diode switch right in the handle
for two settings.

greg

 

[Jim Yanik]

Use an ordinary lamp dimmer;they will handle 100W lamps.

FYI,I mounted a triac-lamp dimmer in a plastic double outlet box,and
mounted a dual outlet in the 2nd space,and use it primarily as a speed
control for my old model 270 Dremel hand grinder.
But I can use it for anything that plugs into a standard 120 VAC outlet.

 

[James Sweet]

I have a 40W soldering iron; I need to solder a small transistor in a
PCB. I guessing 40 watts is too much heat for that task, so could I add
a incandescent bulb in series with the iron to reduce the heat? If so;
what watt lamp? (40, 60, ect) Thanks

It's all in how you use it, I've used a 40W iron (and a few times a 140W
gun) to solder delicate components, and in fact I find it's less likely
to damage things using an overpowered iron where you have the heat on
for only a moment than an underpowered iron where you have to keep it on
the part heat soaking everything.

A light dimmer or diode in series will reduce the temperature of the
iron, but if it were me, I'd use it as-is and try to keep the iron on
the joint for only as long as necessary.

 

[Ross Herbert]

It's all in how you use it, I've used a 40W iron (and a few times a 140W
gun) to solder delicate components, and in fact I find it's less likely
to damage things using an overpowered iron where you have the heat on
for only a moment than an underpowered iron where you have to keep it on
the part heat soaking everything.

A light dimmer or diode in series will reduce the temperature of the
iron, but if it were me, I'd use it as-is and try to keep the iron on
the joint for only as long as necessary.

I would agree with your comments.

In the 60's - 70's when we had our soldering irons on the go 24/7 we
would use the diode switch simply to reduce the temperature during the
periods when the iron wasn't actually soldering anything. It was
simply used as a "standby" position so that it would heat up to
maximum very quickly when the diode was switched out and soldering
re-commenced. When a non temperature controlled iron is left on
permanently without being used it tends to overheat the element and
the tip because no heat is ever being drawn from it as it would during
soldering. Many irons developed black scaling which causes metal to
flake off the tip and the heater element thus resulting in rapid
oxidation and demise of the iron.

As a result, diode switching to standby assisted in prolonging the
life of the heater element and the iron itself.

 

[ian field]

FYI,I mounted a triac-lamp dimmer in a plastic double outlet box,and
mounted a dual outlet in the 2nd space,and use it primarily as a speed
control for my old model 270 Dremel hand grinder.
But I can use it for anything that plugs into a standard 120 VAC outlet.

--
Jim Yanik
jyanik
at
kua.net

There may be concerns about switching spikes damaging the element - but much
depends on the design of the iron.

The iron I use is an Antex X-25 which has a slender rod element which pushes
into a hollow bit, so I imagine the resistance wire in the element is thin
and very compact wound. Despite not using any form of dimming the irons were
only lasting a few weeks (continuous all day use) As my PC often crashed and
there were bursts of crackles on the radio, I guessed that the problem was
caused by line transients. A plugtop transient absorber fitted to the iron's
lead cured the reliability problem - the irons now last over a year. The
moral of the story being - some irons can be damaged by noisy mains!

 

[Jim Yanik]

There may be concerns about switching spikes damaging the element -
but much depends on the design of the iron.

The iron I use is an Antex X-25 which has a slender rod element which
pushes into a hollow bit, so I imagine the resistance wire in the
element is thin and very compact wound. Despite not using any form of
dimming the irons were only lasting a few weeks (continuous all day
use) As my PC often crashed and there were bursts of crackles on the
radio, I guessed that the problem was caused by line transients. A
plugtop transient absorber fitted to the iron's lead cured the
reliability problem - the irons now last over a year. The moral of the
story being - some irons can be damaged by noisy mains!

I have a couple of Antex 15 W irons. I love them!
I used them at Tektronix for 20 years with no problems like that,too.
You must have some BAD power mains.
Perhaps the "transients" are far too high.Your power company should be
notified,have them put a monitor on your line and fix the problem.

 

[g. beat]

Another trick is to use a transformer with secondary taps at various % of
the mains in and wire the secondary antiphase in series with the element
to
subtract voltage from the mains, even easier is an old type transformer
with
several taps for various mains voltages - then its possible to just use
the
primary as an autotransformer.

That is the trick that Heath kit used with the old 6 volt GE soldering
irons.
Transformer had 4, 5 and 6 volt taps - used with rotary switch on front for
Low, Medium and High

gb