Soldering and heat sinks: please educate me.

[kyrreca]

Hi guys.

I'm looking to get started on my first DIY pedal build. I have some soldering practice from modding stompboxes, changing pickups, etc. But this stompbox I'm building has some transistors in it, and I've been told that the heat from the iron may damage the transistors, and I need to use a heat sink to avoid that.

 

However, I don't really understand what heat sinks are, or how they work. I've tried the search function, and I've tried google, but I haven't found anything really helpful, so now I'm turning to the helpful folks of the DIY forum. Could you please tell me a little bit about heat sinks and how they work?

[jonjohn]

what about using sockets. they are good if you put them in the wrong way around.

not positive on what heat sinks you are talking about. but i have read about putting clips on the wire of the transistor to dissipate some heat.

on a side note . they can handle a bit of heat. i havent burnt one out ever. and i have put them in the wrong way taken em out and put em back.

[kyrreca]

OK, thanks.

I've considered using sockets, but, I'd have to order them from http://banzaieffects.com/ and it usually takes 3-4 weeks to get my stuff from them. I want to get started ASAP. Guess I'll try just soldering them the good old fashioned way, and try to be quick so I don't damage anything.

[jonjohn]

you should be fine. make sure you get the orientation right.

what are you making?

[kyrreca]

I'm making a clone of a current production bass fuzz. It's a pretty simple build, but I'm still a little anxious of screwing something up.

[AMZ-FX]

Most of the time I do not put heat sinks on leads before soldering the parts.

 

If I'm soldering germanium transistors or diodes, or maybe mosfets, I put a small copper clip on the legs, solder the connection and then remove the clip. Only takes a few seconds.

 

Don't worry about it on resistors or capacitors.

 

regards, Jack

[NickCaveFan]

 

Most of the time I do not put heat sinks on leads before soldering the parts. If I'm soldering germanium transistors or diodes, or maybe mosfets, I put a small copper clip on the legs, solder the connection and then remove the clip. Only takes a few seconds. Don't worry about it on resistors or capacitors. regards, Jack

 

 

I agree with Jack. If it is a plastic bodied IC, you won't have too many problems as there is a pretty big lead frame within the body to absorb the heat. One thing you can do to help is to tin the leads before you install it or use a socket. The great thing about the socket is it will permit you to try out different ICs and tailor the sound to your taste. Some of the more exotic parts from germanium, diodes, and stuff are more sensitive. Find a vendor datasheet (just search for the part number using Google) will tell you if there is a part temperature sensitivity. Again, tinning the lead before hand will help keep soldering time down later. And just put a metal clip of some sort near the body to help draw the heat away when you tin the lead. Put the tip of the iron near the end of the lead and apply your solder near the body.

[amp_surgeon]

Hi kyrreca.

 

"Heat sink" is a generic term for any object that helps to remove heat from another object by thermal contact. They work by adding a lot more surface area to the object that's being cooled, giving it a chance to dissipate heat into the air more quickly. An example are those metal plates on the back of solid state amps. Those usually have fins so that they can fit more surface area into a smaller space. The processor in your computer probably has a similar type of heat sink on it. It may also have a fan to help air carry the heat away.

 

When they refer to putting a heat sink on a semiconductor before soldering it, they're not talking about cooling the semiconductor - they're talking about keeping it from getting too hot in the first place. The heat travels from the solder joint up the wire and into the transistor. The objective is to stop as much of that heat as possible before it gets to the transistor. This is done by adding surface area to the wire BETWEEN the transistor and the solder joint. A simple way to do this is to clip a metal object onto the wire.

 

There are clips made especially for this. They resemble a wide flat pair of tweezers. Most people just use an alligator clip or hemostats.

 

A heat sink is a safety precaution, and these days it's rarely needed anymore. Silicon transistors are less susceptible to heat damage than germaniums. Most decent quality soldering irons are temperature controlled. Soldering to the copper "land" area on a circuit board doesn't require as much heat as soldering to a terminal lug. Unless you like to barbecue your parts when you're soldering them, it's unlikely you'll damage them with too much heat. Just leave the iron on the joint only long enough to get the solder to flow into place. It also wouldn't hurt to mount your transistors off the circuit board by at least a 1/4 inch or so.

 

BTW, transistors and diodes are not the only parts that can be damaged by too much heat. Any parts containing plastic can also be wrecked by heat, including polyester film and polystyrene caps, trimmer resistors, etc. I've even seen those blue 3PDT Taiwanese foot switches begin to melt down after a few seconds of heating.

[kyrreca]

Thanks for all the help, guys!