The effect of too much soldering heat on Mosfets

Thread Starter

Lumenosity

Joined Mar 1, 2017
636
I am wondering how easy it is to damage a MOSFET (let's use IRF260N for this example) during soldering.

The datasheet calls for no more than 10 seconds at 1.6 mm from the body of the device.

So let's say you go 11 seconds at 310....what can that cause?

Is it more likely to cause a change in the chip function or more likely to cause failure immediately?

I ask because I am not certain, but it seems the temperature of my new MOSFET is running too hot and I'm wondering if it could be because I overheated it during soldering.

So in essence, proper soldering technique and keeping IC's appropriately cool during solder can affect the way they operate (their operating efficiency for example)?

Thanks
 

MrSalts

Joined Apr 2, 2020
712
Maybe you can post a circuit schematic with some photos of your device.

Also, in my experience mild thermal damage first causes small current leakage (less than 1mA) in the off state. But that is with more than a second or two extra heating while soldering. The soldering recommendation usually has some safety factor built in so a bit over on time is not usually going to cause damage.

Mosfets running hotter than expected usually an issue of gate voltage not turning the device completely on, or completely off.
 

Audioguru again

Joined Oct 21, 2019
3,828
What is wrong with your soldering technique that takes 11 seconds to make a 1 second soldering connection??
The IRF260 package is made to be bolted to a finned heatsink for cooling.

A class-A audio amplifier is actually a room heater that makes sounds sometimes.
 

BobaMosfet

Joined Jul 1, 2009
1,896
@Lumenosity Think about what @Audioguru again said- he's right. If you are taking that long to solder, then you have an issue in one of these areas:

  1. technique - how/where to hold the iron
  2. equipment - iron not hot enough/misfunctioning/set wrong
  3. joint - joint is dirty, using insufficient flux
  4. copper - copper layer that the joint is at is large enough it's dissipating heat too quickly, use a hotter iron for less time

My personal golden rule- no more than 5-seconds on a pin. And I will wait between soldering pins, if necessary to let the device cool down some before moving on.
 

Audioguru again

Joined Oct 21, 2019
3,828
On You Tube videos, they carry solder around on the filthy dirty tip of a overheated soldering iron then dab the solder on the connection. The flux in the solder was burned away long before the connection was made into a cold soldering joint.
 

Thread Starter

Lumenosity

Joined Mar 1, 2017
636
What is wrong with your soldering technique that takes 11 seconds to make a 1 second soldering connection??
The IRF260 package is made to be bolted to a finned heatsink for cooling.

A class-A audio amplifier is actually a room heater that makes sounds sometimes.
May I ask what in this thread gave you the impression that there was a problem with my soldering technique ?
I don't recall saying I heated it too long, just asking what the result would be "if I did".

Discussing soldering technique is counter productive to this thread. The question is what (if any) indications would there be (if any) if for any reason a mosfet were overheated during soldering (the most likely scenario). Even slightly.
 
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Thread Starter

Lumenosity

Joined Mar 1, 2017
636
@Lumenosity Think about what @Audioguru again said- he's right. If you are taking that long to solder, then you have an issue in one of these areas:

  1. technique - how/where to hold the iron
  2. equipment - iron not hot enough/misfunctioning/set wrong
  3. joint - joint is dirty, using insufficient flux
  4. copper - copper layer that the joint is at is large enough it's dissipating heat too quickly, use a hotter iron for less time

My personal golden rule- no more than 5-seconds on a pin. And I will wait between soldering pins, if necessary to let the device cool down some before moving on.
Except, if you had read and understood the context of the OP you would have understood that it was never stated that it would take that long to solder a simple joint. Even though the official datasheet describes 10 seconds for soldering to be factual.

The supposition was for the "sake of the argument / discussion"
Again, this thread is about the effect of heat on a mosfet, not how the heat got there or soldering technique.

Thanks
 

DickCappels

Joined Aug 21, 2008
7,954
It was about 1985 when logic level MOSFETs became available. I swapped out the six Darlingtons on the motor drive amplifier for TO-220 MOSFETs, switched the circuit on but noting happened. The board was upside down on the workbench and I went to measure the voltages to see what was happening. Then there was a tiny "thunk" as one of the MOSFETs go so hot that it unsoldered itself and fell onto the bench. It was late at night and no distributors were open, so I put the MOSFET back on the board, fixed the short and the motor ran beautifully. After that I did not worry about soldering time.
 

Audioguru again

Joined Oct 21, 2019
3,828
The question was, "What will happen to a Mosfet if its soldering took 11 seconds?"
Answer, "I do not badly solder like that so I guess that some Mosfets would be ruined."
 

Thread Starter

Lumenosity

Joined Mar 1, 2017
636
The question was, "What will happen to a Mosfet if its soldering took 11 seconds?"
Answer, "I do not badly solder like that so I guess that some Mosfets would be ruined."
I'm sorry the point of the thread clearly was missed.
How else would one describe a way that mosfets would commonly get too hot that is simple and not confusing and drives the point?
Thanks for your efforts.
 
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