Homebrew PCBs

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From: - Wed May 08 19:31:50 2002
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Date: Wed, 08 May 2002 19:31:50 -0700
From: "David L. Miller" <David.Miller@...>
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To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Re: hot air soldering comments
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I don't know what the "proper" preheat temperature is, but I can tell
you that when our contract manufacturer re-works a board for us at work,
they bake it at 125C (~250F) for 24 hours before they touch a chip. So,
you should be able to heat to 200F "forever" without damaging anything...

tedinoue wrote:

 > Hi Guys,
 >
 > Thanks for replying. I have referenced Hans' links and the others in
 > the past and made the hot-air-pencil -- that works fine. My real
 > questions lie elsewhere
 > Hans indicates that preheating is necessary. ok, one question down.
 >
 > The outstanding questions are:
 > What is the proper preheating temperature?
 > Is there a maximum time you should preheat the board/components
 > before damage can set in?
 > What can I do about unmelted solder paste that has moved under
 > surface mount caps?
 > What do you do about the tiny cap components blowing away, even under
 > very minimal air flow? I've read a tiny dab of epoxy. What do others
 > do?
 >
 > Thanks,
 > Ted
 >
 > --- In Homebrew_PCBs@y..., Steve Greenfield wrote:
 > > Yup, Hans, your page has been in the bookmarks of the Group home
 > > page for weeks!
 > >
 > > Hint, hint, everyone, check out the Bookmarks at the Group home
 > > page once in a while. Also a reminder to add useful links.
 > >
 > > http://groups.yahoo.com/group/Homebrew_PCBs/links
 > >
 > > Do you think one of those warmer plates would work? Not a hotplate,
 > > I mean those glass warmer things. I was just figuring they are
 > > pretty cheap at the thrift store.
 > >
 > > Also a reminder that when you do this, the solder paste must be dry
 > > before you start trying to solder, or any fluids will boil and push
 > > the parts off the pads. Should be able to do that by warming it up
 > > on your pre-warmer for a bit.
 > >
 > > Steve Greenfield
 > >
 > > --- hans@c... wrote:
 > > > Ted,
 > > > I made a Hot Air Pencil and published the idea several years ago
 > > > at my
 > > > web site.
 > > > The single most important item is the heat exchanger. In my
 > > > design I
 > > > filled it with stainless steel
 > > > wool and that made a vast difference.
 > > > Pre-heating the board is required.
 > > > http://hans-w.com/surfacem.htm
 > > > hansw
 > >
 > >
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