Solder Paste

[AtomSoft]

Can someone recommend some good solder paste for soldering SMT/SMD parts. I have seen it like a grey blob and you use a squeegee to wipe it over a stencil.

heh anyway where can i get that nice grey solder paste? or something similar in texture thats solder paste?

 

[ronsimpson]

I use solder paste from DigiKey. I do not use a stencil. I use a tooth pick and place some on each pad. Then stick down the parts. Then I use a toaster oven to heat the entire board.

 

[AtomSoft]

Cool. I plan to make my own custom stencils at home. I got a process in my head but not tested and i need to collect parts. But anyway. Which solder paste? How much it comes with.

 

[cr0sh]

Cool. I plan to make my own custom stencils at home. I got a process in my head but not tested

I'm curious about what kind of process you are thinking of. Short of a laser cutter (which I don't yet consider homebrew due to cost), the only other homebrew process I could think of would be to etch a piece of sheet copper with the pad layout (inverted) ironed-on; similar to a PCB. The only problem would be the amount of toner needed on each side of the copper sheet, the accurate alignment needed on both sides, plus the fact that the etchant would eat the copper from the inside edge of the holes.

I suppose -maybe- one might be able to build a laser "burner" using a CD-RW/DVD-RW (or even blu-ray) laser head; and burn the holes into black plastic, but I am not sure how well that would work!

Ah well - all ideas at the moment; I have yet to even try making my own PCB, never mind dealing with SMT...

 

[AtomSoft]

I Dont think the etchant would eat the copper from inside edge. Its the same way a PCB would be made. If that was the case a PCB Wouldnt be etcehd at all heh.. I do plan on doing it this way. But i have my own bag of tricks to add to the process.

 

[DirtyLude]

A lot of us use the DX Solder paste. Works well and it's cheap.

**broken link removed**

 

[AtomSoft]

Nice!! Thanks a ton!

 

[RCinFLA]

Solder stencils are made from brass sheet. Several methods have been used from CNC milling to photo etching.

Unless you are building a board with a lot of components or doing a large quantity of assemblies, for single build you are usually better off just using a fine point pencil solding iron with small gauge solder wire. This works to about 0.05 inch (50 mil) lead spacing.

For tighter then 50 mils lead spacing, pre-tin pads and place component with a hot air or butane soldering pen with hot gas tip. I prefer the butane hot gas pencils as they provide hotter gas with less 'wind' velocity of hot air soldering devices.

If you can get Carbon Trichlor solvent it is best for cleaning SMT boards after soldering. Otherwise use 90% Isopropyl rubbing alcohol. A small 1" paint brush cut back to about 1/2" to 3/4" brissles is good for cleaning.

 

[AtomSoft]

I can get the copper sheet cheap about 4x6" for $2.50. Also i have all the supplies needed for photoetching. It would actually save me toner if i photo etch the stencil. Since i can reuse it. I use the Toner transfer method for PCBs tho. But since i have tons of stuff here for photo etching i can make stencils with it.

I can also get brass 5mil 4x6' same size as copper sheet but for $4 little more expensive. Ill get both and run some test. I dont use the chloride to etch. I use my own mixture. The Muratic Acid and Peroxide. Im sure i can adjust proportions to etch nice and smoothly.

I have alcohol (Isopropyl ) but 50% i guess i need the good stuff. Thanks for the brush tip also!

 

[cr0sh]

I Dont think the etchant would eat the copper from inside edge. Its the same way a PCB would be made. If that was the case a PCB Wouldnt be etcehd at all heh.. I do plan on doing it this way. But i have my own bag of tricks to add to the process.

Your copper sheet is going to be fairly thick compared to the copper layer on a PCB, unless you can find copper sheet as thin as the layer on a PCB (and I am not sure how well that would work as a stencil - whether the strength would hold up to the work). It may still be tricky timing it right, especially on narrow and closely spaced trace widths. I wish you all the luck in the world, though! I don't know if such a method would be cheaper than having a stencil made from plastic or other material (copper sheet isn't cheap - though maybe at the thickness you might be working with it won't be too bad?), but it might be worth it for one or two-off hobbyist PCB production...

Good luck, and let us know how it turns out!

 

[3v0]

I have heard of people using brass shim stock.

I use a cricut to cut mine in plastic.

 

[AtomSoft]

Thanks. I guess the thickness is key But im sure it would be ok as long as i can get a nice thin layer.

 

[Larry Lamb]

good luck with this! Seems brave I've used DX paste, it is fine. I always use a stencil tho and my pcb board manufacturer gives me one foc when i order from them!

 

[AtomSoft]

heh since i do home made PCB i need to do home made stencils (seems like the only way). Why am i going to pay $10+ for a stencil when i wont pay that much for a PCB. I make a PCB now andit cost me about $2 or less. I was going to try Batch PCB for my ARM stuff just because they seem more important. Like i was going to make adapters for my own board. This way i can reuse the uC

 

[3v0]

I cut mine in overhead projector transparencies. Not sure about the thickness.

There is a give and take between the stencil thickness and the size of the holes. When you get to devices with fine pitch you sometimes have to lengthen the stencil holes to get enough paste down.

 

[mvs sarma]

they are of 3 to 4 mil thickness !!

 

[f.murch@sbcglobal.net]

Try **broken link removed** It is fast and has a better price