Soldering and Heat Damage ?

[Phil Hystad]

Back when I was a kid and doing a lot of experimenting, I would sometimes build a transistor based project.  I was comfortable with tube circuits but never with anything solid state.  One fear I had was destroying transistors with heat from a soldering iron.  I was taught to always use a heat sink on the leads between the soldering point and the device to protect the transistor or diode from the heat.

Then, I left electronics and experimentation.  I have this big gap dating between 1967 and 2008.  In 2008 I built my first kit since those days of the early to mid 1960s.  In building this kit, the parts were all to be mounted on PCB with virtually ZERO room to connect any heat sink.  I used a very nice temperature controlled soldering iron with a recommended pencil style tip.  The result was that the kit worked (a small audio oscillator and amplifier).  But, I was fearful that I was toasting my transistors and the two ICs that were part of this kit.

I have read several soldering notes, including the one on Elecraft, and they do not specifically mention heat damage to components and what you need to do to avoid that sort of thing.  They may hint at it though by recommending the temperature controlled soldering irons and things of that ilk.

So, how much danger is there in destroying ICs, transistors, and such with a soldering iron applying such components to a PCB or maybe even using some kind of ugly construction?

phil, K7PEH

PS.  Merry Christmas -- the kids and grandkids have not arrived yet this morning so I have time to ask questions.
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[Bill W4ZV]

Phil Hystad wrote

So, how much danger is there in destroying ICs, transistors, and such with a soldering iron applying such components to a PCB or maybe even using some kind of ugly construction?

Very little if you use a temperature-controlled soldering iron at ~700F.  The solder will flow quickly and you will be done before any temperature damage can occur.  There's a much higher risk of damage from improper ESD handling than overheating components.

73 & Merry Christmas!

Bill

[Don Wilhelm-4]

Phil,

To amplify what Bill W4ZV said, you are not likely to have a heat
problem with a 700 deg F temperature controlled soldering station.
That assumes that you use a tip with adequate heat mass to conduct heat
to the solder connection.  I personally prefer a 3/32 inch screwdriver
tip over a conical tip because the larger surface of the screwdriver tip
will conduct heat to the solder connection more quickly.  Note that this
is my personal preference, many have good success with the conical tips.

Remember that it takes a combination of time coupled with high
temperature to damage components.  You are more likely to create damage
with too low a temperature applied for a long time than with a higher
temperature applied for a short time.  Watch the solder and check the
time it takes for the solder to flow out onto both the solder pad and
the component lead to an almost invisible edge -if it flows out in less
than 2 seconds, the iron temperature is too high, but if it takes longer
than 3 seconds, the temperature is too low.  Since the iron dwell time
depends on the size of the solder pad and the size of the component lead
(larger copper areas will conduct heat away from the connection), you
may find you have to increase the heat or switch to a larger solder tip
when soldering things larger than the average component lead and solder pad.

Another related point for those who are accoustomed to soldering onto
lugs and other "old Heathkit" items, the Elecraft boards have
thru-plated solder pads, and it is sufficient only to fill the hole with
solder - I actually prefer to have a very small fillet of solder, but it
is easy to use too much solder and end up with a big blob on the board.  
To more easily control the amount of solder applied, use a small
diameter solder - I normally use 0.15 inch, but 0.20 inch diameter will
do with care - I cannot recommend larger solders than .020 inch although
many others say 0.25 inch is OK.

73,
Don W3FPR

Phil Hystad wrote:
> Back when I was a kid and doing a lot of experimenting, I would sometimes build a transistor based project.  I was comfortable with tube circuits but never with anything solid state.  One fear I had was destroying transistors with heat from a soldering iron.  I was taught to always use a heat sink on the leads between the soldering point and the device to protect the transistor or diode from the heat.
>
> Then, I left electronics and experimentation.  I have this big gap dating between 1967 and 2008.  In 2008 I built my first kit since those days of the early to mid 1960s.  In building this kit, the parts were all to be mounted on PCB with virtually ZERO room to connect any heat sink.  I used a very nice temperature controlled soldering iron with a recommended pencil style tip.  The result was that the kit worked (a small audio oscillator and amplifier).  But, I was fearful that I was toasting my transistors and the two ICs that were part of this kit.
>
> I have read several soldering notes, including the one on Elecraft, and they do not specifically mention heat damage to components and what you need to do to avoid that sort of thing.  They may hint at it though by recommending the temperature controlled soldering irons and things of that ilk.
>
> So, how much danger is there in destroying ICs, transistors, and such with a soldering iron applying such components to a PCB or maybe even using some kind of ugly construction?
>  
>
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[Jack Smith-6]

Robert Pease, in "Troubleshooting Analog Circuits" (p. 82) provides a
useful anecdote on the subject of modern silicon semiconductors and
soldering iron heat:

    ...Overheating does not by itself cause failure. I once applied a
    soldering iron to a 3-terminal voltage regulator--I hung it from the
    tip of a soldering iron and then ran off to answer the phone. When I
    came back the next day, I discovered the TO3 package was still quite
    hot-- +300C, which is normally recommended for only 10 seconds. When
    I cooled it off, the regular ran fine and met spec. So, the old
    dictum that high temperature will necessarily degrade reliability is
    not always true. Still, it's a good practice to not get your power
    transistors that hot, and to have a base drive that call pull the
    base OFF if they do get hot.


Pease also offers the following comment in discussing equipment
necessary in any well equipped lab (p. 23):

    A suitable hot soldering iron. If you have to solder or unsolder
    heavy busses from broad PC-board traces, use a big enough iron or
    gun. For small and delicate traces around ICs, a small tip is
    essential. And, be sure the iron is hot enough. An easy way to
    delaminate a trace or pad, whether you want it or not, is to heat it
    for too long a time, which might happen if your iron weren't big
    enough or hot  enough. (The old Heathkit warning not to use a hot
    iron became obsolete along with the germanium transistor.) In some
    cases, a grounded soldering iron is required; in others a portable
    (ungrounded or rechargeable) soldering iron is ideal. Make sure you
    know whether your iron is grounded or floating.

Bob Pease should need no introduction, but for those not familiar with
him, a good starting point is http://www.national.com/rap/

Jack K8ZOA
www.cliftonlaboratories.com


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[Jack Smith-6]

Robert Pease, in "Troubleshooting Analog Circuits" (p. 82) provides a
useful anecdote on the subject of modern silicon semiconductors and
soldering iron heat:

    ...Overheating does not by itself cause failure. I once applied a
    soldering iron to a 3-terminal voltage regulator--I hung it from the
    tip of a soldering iron and then ran off to answer the phone. When I
    came back the next day, I discovered the TO3 package was still quite
    hot-- +300C, which is normally recommended for only 10 seconds. When
    I cooled it off, the regular ran fine and met spec. So, the old
    dictum that high temperature will necessarily degrade reliability is
    not always true. Still, it's a good practice to not get your power
    transistors that hot, and to have a base drive that call pull the
    base OFF if they do get hot.


Pease also offers the following comment in discussing equipment
necessary in any well equipped lab (p. 23):

    A suitable hot soldering iron. If you have to solder or unsolder
    heavy busses from broad PC-board traces, use a big enough iron or
    gun. For small and delicate traces around ICs, a small tip is
    essential. And, be sure the iron is hot enough. An easy way to
    delaminate a trace or pad, whether you want it or not, is to heat it
    for too long a time, which might happen if your iron weren't big
    enough or hot  enough. (The old Heathkit warning not to use a hot
    iron became obsolete along with the germanium transistor.) In some
    cases, a grounded soldering iron is required; in others a portable
    (ungrounded or rechargeable) soldering iron is ideal. Make sure you
    know whether your iron is grounded or floating.

Bob Pease should need no introduction, but for those not familiar with
him, a good starting point is http://www.national.com/rap/

Jack K8ZOA
www.cliftonlaboratories.com


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