Stencils and reflow beginner

Michael a écrit :

No. TH parts aren't designed to withstand the SMD process temperatures.

It's not that you can, but rather that you must.

No. BTW your solder past screen will normally allow paste deposition on SMD pads *only*.

AS yopu have to mount TH parts after the question makes no sense, but even if you would and have solder past on TH pads to, you'll probably have a lot, if not most/all, of bad TH parts solder joints.

SNIP

You do just the smt parts first. The stencil should only put down paste on these parts, leaving all TH parts /pads without solder.

Paste is for SMT parts. But why use it? You sound like a hobbyist. Paste has a limited life once opened, is expensive and needs to be kept in the fridge. Use this instead SSD technology

Great!

Exactly what I needed to know.

I'm getting so sick of soldering resistors, diodes and caps in my small production products that I need to start looking at doing these SMT and then the IC sockets and bulkier parts later.

Just doing those common components is going to save at least half the work.

The stencil system looks interesting but I was also wondering if I can't just use a normal screen process to laydown the paste.

I use a standard monofiliment screen and film emulsion and lately, have been using water based inks.

I'll look into it but wonder what the actual screening process is like for the paste? Can the screens be cleaned up with water...or do they need a solvent based cleaner?

I'll look into the "sipad" as well......is that a screen process too?

There are actually some desktop pick and place machines I saw on this site for just a few thousand.....I need to head this direction. (!!)

StencilsUnlimited.com has a SynTECH paste that doesn't need refrigeration and has a 6 month life span after opening (12 months in the fridge). I've had no trouble using it with a hotplate.

I got the syringe. No stencils, I just "tap" tiny dots of paste onto the pads. I tried squeezing it out, but it doesn't stick as well that way, and I ended up with way to much paste.

Yes but you don't need to know about it. They send you a board with solder, adhesive flux and a paper backing that you peel off when you're ready. So you do have to send them your PCBs for the process, and it does seem like it's much better suited to single sided boards. But the good thing is you can pick and place your parts until they are lined up correctly, the solder is solid.

Great times we live in eh?

Have you considered looking for a contractor? It's really the best in the long term. You should focus on your product, not the details of the production.

I'm not doing the quantity that would interest a contractor, I would think.

Besides, I enjoy the hands on part. Not to mention some of the incredible buys on surplus components I've been geting on Ebay.

That's the best part. (Sorry Digi Key).

However, your quantities do make a difference in what is easier and reliable at home. What quantities are you doing?