Tools for PCB cutting/drilling?

DC_Kid

Joined Feb 25, 2008
1,072
i myself need a reflow oven. one of my projects demands i use SMT so i can shrink the footprint into a user friendly package.

i was gonna build it all from scratch, but there are way too many off-the-shelf items to build a kit.

i found this neat programmable controller for toaster overs (http://thesiliconhorizon.com/store/silicon-horizon-techfx-reflow-making-your-reflow-oven-p-48.html). however, i dont want to use a generic toaster oven. IR lamps are easy to obtain in 120v and 240v. i will build a box like a toaster oven except i will have upper and lower IR lamps and a convection fan. the upper lamps will have a fixed 1/4" aluminum deflection plate, and the lower plate will be of 3/8" thick teflon coated aluminum, and is removeable. i'm thinking the bottom plate will slide in/out on some side rails.
 

millwood

Joined Dec 31, 1969
0
I understand that with SMD ICs the solder typical flows behind the lead (towards the body of the IC package),
that is the problem with the copper braid approach. when you put the braid on the solder and almost inevitably some solder will be pushed back behind the leads and when that happens, it is next to impossible to get them out. and there is a good chance they will create a short somewhere there.

I think the solution might be to control the amount of paste and/or to use suction when braiding.
 

DaveH

Joined Jan 1, 2009
53
Hey DC, I just looked at that link. My first reaction is not about PCB SMD techniques thought. That girl looks gorgeous! She looks like a typical electronics enthusiast. When my project is done I'm gonna find out about her to take a photo of her holding my circuit board so lots of people will buy it:D

I'm in England, we're not that advanced here and I was getting confused about toaster ovens. I thought you mean like a toaster for sliced bread. You actually mean like those ovens they use in Subway fast food joints, where they toast those big subs with chicken teriyaki. That makes sense now. Amazing those can be used for SMD.

Jpan, about lead pitch, the chip I'm using has an average lead width of 0.22mm. The lead pitch (says the data sheet) is 0.5mm, but the data sheet defines the pitch as the distance between the centre points of adjacent pins. This means that the gap between pins is 0.28mm. If you've done it down to 0.025 that's a pitch of 0.6mm, surely you could also do 0.02/0.5mm, which gives me some hope. Thanks
 

DaveH

Joined Jan 1, 2009
53
Hi Millwood, I didn't see your last post, before my previous post. I see what you mean but Jpan has reported success for lead pitch that is pretty close to what I need, I guess it's a bit hit and miss. I was thinking about continuity checks between pins, if there's too much solder with these tiny pins you may get a bridge that forms even between pins that aren't even adjacent, like pins 1,2,3, that would be a nightmare. For suction with a solder sucker you'd have to keept reloading the plunger. I just had another idea, you could take the nozzle of a teflon coated solder sucker tip, and modify it to fit on a vaccum cleaner hoze then you'd get continuous suction.
 

jpanhalt

Joined Jan 18, 2008
11,087
Why make it complicated and try to invent a new method with a continuous sucker?

Use a fine solder wick, be sure it is properly fluxed, heat the wick and not the solder. It helps to have a little solder on the iron's tip for heat conduction, but the flux also helps in that regard. Frankly, I don't see how you are going to "push" solder behind the pins by heating through the solder wick.

John
 
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