reflow profile questions from a noob

Questions about the BatchPCB service

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uncle4
Posts: 20
Joined: Wed Oct 28, 2009 2:11 pm

reflow profile questions from a noob

Post by uncle4 » Tue Mar 22, 2011 6:33 am

Hi there.

I'm awaiting my first set of boards from BatchPCB, have an oven all
set up and can't wait to burn something. In the meantime, I realized
I forgot whether I ordered leaded or lead-free solder on my boards. I
can't find a page on batchpcb.com to tell me which I ordered.

My questions are:

1. Can you tell by looking at the solder pads whether you've got leaded
or lead free solder pads?
2. Is there a happy-medium regarding reflow profiling that might work
for both types of solder?
3. If you have components that suggest a different reflow profile than
the solder mask or other components, how do you reconcile the differences?

Thanks tons for any suggestions!

Slainte!

skimask
Support Volunteer
Posts: 1244
Joined: Sun Nov 09, 2008 2:11 am
Location: Minot, N.D.

Re: reflow profile questions from a noob

Post by skimask » Tue Mar 22, 2011 7:12 am

1 - Assuming the soldering was done correctly and cleanly in the first place, leaded solder should be shiny, whereas most type of unleaded solder (almost sounds like types of gas now doesn't it? :) ) will have a frosty appearance. A good unleaded solder joint generally almost looks like a leaded cold solder joint. Problem is that there is more than one type of unleaded solder, and they have different melt points, reflow characteristics, and so on. Someday, we'll all settle on another perfect standard.

2 - Not really. You can't "split the difference" because of the differing temperatures that each types melt at. And you won't really be able to figure that out without knowing exactly what type of solder, if it's unleaded, you've got on the board, if you're actually got unleaded on there.

3 - Not 100% sure on that and don't want to spread bad info, but, if I had to guess, I'd say go with the least 'aggressive' reflow profile (i.e. lowest peak temps, least amount of time in the oven, etc) and see what happens.
I ignore "one post wonders".

EChrisDenney
Posts: 2
Joined: Tue Mar 19, 2013 6:42 am

Re: reflow profile questions from a noob

Post by EChrisDenney » Tue Mar 19, 2013 6:56 am

Hi Uncle4

1. Are you referring to the "surface finish" on the bare PCB? If so, then you likely can't tell the difference very easily. But the melting points of leaded and lead-free aren't terribly different, especially for the small amount of solder that is cover the copper on the bare PCB.

2. Let me know what kind of heating device you're using and I can help you identify a good profile.

3. Components are surprisingly robust. Take a look at your most delicate components and design your profile to comply with that one, so that you don't damage it. The larger components may take more heat than the most delicate components. It can be tricky sometimes. But believe it or not, reflow soldering is pretty darn easy.

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