<$500 preheater

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dknguyen

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I had underestimated how difficult it would be to solder a heavy copper 2.5oz board with lots of planes (4 layers and many plane connected pins with no thermal relief). Using leaded solder and a JBC station, it feels like working with lead-free solder. Won't be making that mistake again for a prototype-run that has to be hand soldered.

Anyways....I basically want a preheater to get around this but they are all at least $1000+ and many are $2000+. Does anybody know of cheaper ones? Or jerry-rigged setups (hot air gun maybe? even a fancy temperature controlled hot air gun is cheaper than the preheaters that I see). The JBC can just barely the pins that are not connected to a plane but the pins that are connected to a plane throws a huge wrench into the works.
 
I've heard of hobby assemblers doing SMT work with toaster ovens.

Or maybe an IR heat lamp?
 
PCBs are 8"x8"

that infrared burner is so cheap it might be worth a shot.

hmmm IR heat lamps are an idea.

I would ultimately prefer convection over IR but I know of no small flat, low air flow electric heaters and they all have tipping protection. Thanks for the ideas.
 
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I also have made that mistake DK.....I know exactly what you are talking about.

What I did, when my wife was not around, took my boards and the iron to the kitchen. Our oven has the same infrared burners that BoBW showed in his post.
I preheated the board close to 120C (assisted with an IR thermometer whose emmisivity had been calibrated for the PWB material), and finished up the soldering with the soldering iron.

Somewhat uncomfortable with all that heat so close to the hands, but it worked.
 
Ahhhhhhh lead solder in the kitchen!
 
Those gun-type soldering irons are good and powerful, and they heat up very quickly and cool to a safe temperature quickly. Mine is the tool of choice when soldering wires other than small ones onto pcbs.

Downsides are:-
You have to be careful not to leave them on, and with prolonged use the whole thing will get hot. They weigh enough that it is easy to put them down and push something against the trigger so they stay on. I recommend an additional switch and a warning light if that additional switch is on.
The tips burn out fairly quickly. They are cheap and easy to change, but worth keeping some handy.
The iron is heavy.
The tip is quite big, and so useless for all but the largest surface mount pads. Even when I was struggling to solder on an aluminium board, the instant heat iron was just too big to use and I rigged up a hotplate.
There is a big magnetic field from the current, so small magnetic items will be lifted when soldering if not held down.

Bonus upside:
Any bit of wire can be used as a bit, and that can be used for cutting polystyrene (styrofoam) or other plastics.
 
dknguyen said:
Ahhhhhhh lead solder in the kitchen!
Click to expand...

Lead boils at more than 3100°F. What vapor pressure does it have at 650°F soldering temp? LBL National Lab says lead vapor is a non-issue.

What is your concern with lead in the kitchen?
 
I use solder paste on the pads, then put the board in the toaster oven.
I do not use "preheat".
Put the cold board in. Watch the largest part to see when its pads melt.
Small parts go first. Some where a large part, likely in the center, will go last.
Then turn off the power. Slowly open the door. Wait 2 minutes. Done.

I do not watch the temperature. I watch for flowing solder. (use max heat)

I got a used toaster oven at the used store for $5. After the oven disaster of 1980 I am banded from the kitchen. I was etching my PCBs in the oven because the acids work faster when warm. How was I to know that acids eat the inside of the stove.
----edited----
Solder paste is gray while molten solder is shiny. I shine a torch (flash light) in the window and see if all the big pads are shiny.
 
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Legend has it..........Henry Ford actually tested his first gas engine in his kitchen. His wife Clara pouring gas into the carburetor.

Now, that is an understanding wife!
 
kinarfi said:
Does anyone know of a problem with these?
Click to expand...
Got my Weller in the 70's, still works like a charm.

BTW, having no thermal reliefs is bad design practice even for boards that are wave or reflow soldered. Guaranteeing proper solder flow through to the center of the board requires significant changes to a "normal" thermal profile. Plus, somewhere down the road some poor schmuck has to rework your work. How well do you think the hole plating will stand up to a 250 W iron?

ak
 
Another option for hand soldering:
I use solder paste on all the pads. Then hit each pad with the iron. With solder paste I do not have to hold the solder in one hand. I can use my free hand to hold down the part.
 
gophert said:
Lead boils at more than 3100°F. What vapor pressure does it have at 650°F soldering temp? LBL National Lab says lead vapor is a non-issue.

What is your concern with lead in the kitchen?
Click to expand...

Who said anything about vapours? Breathing lead isn't the only way for it to get into you, and people don't inhale food made in the kitchen. Lead is soft enough to leave behind residues and even if it wasn't, the soldering produces both visible and invisible particles of lead everywhere in the soldering area. If you have the appropriate coloured work area or wipe down your work area, you will see it. It seems to be produced most prominently everytime you clean the tip either a sponge or brass wool, but appears to be produced other times as well.

ronsimpson said:
Another option for hand soldering:
I use solder paste on all the pads. Then hit each pad with the iron. With solder paste I do not have to hold the solder in one hand. I can use my free hand to hold down the part.
Click to expand...
Yeah, that's what I ended up having to do with some ICs but it doesn't work in certain instances that require more precision, or for small discretes, or components that have corrective jumper wires.
 
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