Hot Plate Soldering

Tonight I stopped at Target to pick up a hot plate to try out hot plate soldering. I ended up spotting a Bella Pastry Tart Maker which really caught my eye due to its small size. All the other options were excessively large for anything I’d probably be cooking on it. So, I picked it up and decided to try it out. It doesn’t appear to get quite hot enough. I’m going to pick up an IR thermometer to measure it before I give up and maybe add a copper or aluminum plate between the module and the plate.

To me this seems like the best method since it allows you to readjust things while they’re being heated and I have full visibility during the process. I know some of you are using toaster ovens. Is anyone else using a hot plate? What hot plate model are you using?

Also, I did have too much paste in some spots. I’m still trying to get a handle on how much that stuff grows after it starts warming to room temp. It almost doubles in size.

Looks like it heats a bit fast.

I have never been able to get the speed right, but I think the paste is suppost to dry out, then melt, without flowing before melting. What you are seeing(and what I almost always see when I do hot air rework) is the flux melting and flowing, taking the solder balls with it. If it heats slowly enough then the paste dries and solidifies before it melts…

When i did my fryingpan test on a gas stove i pasted with cold paste (at about 10 degrees C) then whacked it in the pan. It stopped the room temp spread problem. It still took a while to melt and flow properly. Since those tests ive bought a cheap hot air reflow station which i have to say is a thing of beauty. Nice cold paste first then run the gun :slight_smile:
Lovely results especially under the gadgeteer sockets.

I’m not using a stencil on this just a toothpick. It’s hard to get it all down before it warms up. I’ve had good sucess with hot air but I like the idea of being able to flow the entire board at once. I’ll keep trying… :wink:

@ ianlee74 -

did you try putting another blank epoxy between the plate and the board to sold, just to slow down the warm up…?

Less is better. :slight_smile:

:slight_smile: i will be tooth picking on my next module as i changed the design after the stencil was made (Sorry Justin!) i only have a few pads to do so it shoudl be ok. Even if the paste spreads a little i have found that as soon as it starts to flow it pulls itself back to the pad (and leaves a little flux behind as a coating to remind you)

No, I’ve only tried the one test which showed that the plate isn’t getting hot enough. I had to hit it with the hot air to get everything up to temp enough to finish flowing. I’m probably going to end up getting a different hot plate. I think this one is made to only get warm enough to put a little brown on pastries. My hot air works best between 350C - 400C.

Less what? Paste? I’m definitely learning that the paste goes a lot further than I expected.

Yes less paste. Just need enough to solder the underside and just a little up the sides.

That’s what I want but I haven’t quite perfected the practice of actually doing it yet. Perhaps at tonight’s NashMicro meeting we’ll get it perfected :wink:

EDIT: BTW, we had enough RSVPs that we’ve had to move the meeting to a larger location :smiley:

@ ianlee74 wow that’s hot on your hot air. I use mine at 250C and it works perfectly. Are you using lead free paste?

No. I’m using this:

Perhaps I’m just not as patient as you :wink: My iron is usually set at 350C so I usually run the hot air at about that temp also. The only socket I’ve melted so far was when I got up to 400C so I try not to go that high unless something gets stubborn. I’ll try at 250C and see what happens. I’m all for running at a lower temp with the air.

If you haven’t, try to get a needle point for your solder paste syringe. Much easier to apply via a thin stream than try to toothpick it into shape :slight_smile:

See the ebay link above. I was using that needle but I was still having a hard time not putting on too much. I remembered today that I do have a smaller needle in my glue box that I’m going to try next. After seeing this post a few days ago, I decided to try the toothpick method. He makes it look very easy.

yeah ok… yes seems like you must go smaller :slight_smile: But you really do need only the tiniest amount of the stuff. Age though can also vary the consistency and how easy or not it is to get the paste onto the pads (says the guy who has two tubes in the fridge and has used them a sum total of two times since buying them 6 months ago)

I realize by the time you read this, it’ll be too late for tonight’s meeting, but if you ever need to change the details (such as the location) of an event in community megaphone, just drop me an email, or you can use the feedback link on the site.

Thanks, devhammer. I didn’t really think to do that until the night before but I didn’t bother since the update was in the post that was linked from the event description. Unfortunately, I don’t think many people in Nashville use your site. Nashville has it’s own calendar that more of the user groups are plugged into. I’ve suggested that they plug into the same network you use but I don’t think any movement has been made.

Yep. Always tough to get folks to adopt something different than what they’re used to. Basic human nature.