How are thru-hole headers with heat sensitive plastic handled during PCB assembly these days? Are they soldered manually after reflow? Basically, I'm wondering whether the board spec (drill hole diameter) should call for the header pins having a tight or loose fit. A tight fit would make the manual soldering process easier IMO.
That's what we do. We experimented with stencil-pasting the thru-holes and running them through the oven with the rest of the parts, but QC didn't like the results.
Tight fit keeps the pins aligned better.
You can also get surface-mount pin headers. Samtec has some nice ones, with alignment pins too.
John
Through hole parts are normally flow (wave) soldered, as a separate production process. With the plastic part of the header on the opposite side of the PCB from the solder wave, of course. Normal plastic headers will take this amount of heat without melting - that is how they are designed to be soldered. They don't float up in my experience.
The through hole ones are much, much cheaper. Stronger too.
-- John Devereux
I'll give you the "stronger" -- although the SMT ones seem "more than strong enough" unless you go for the really low pin-count parts -- but are through-hole ones that much cheaper if you stick with the same manufacturer such as 3M or Amp or FTC? I'm just thinking here that I've gotten dual-row through-board headers from, e.g., Jameco, and while they were quite inexpensive, the quality was definitely several notches down from the considerably spendier offerings from 3M.
---Joel
I'm thinking of the "standard" single or dual row 0.1 inch pitch,
0.64mm(?) square pin types here. They were about $0.003 per pin last time we bought a load. I have never had any quality problems with the ones we get. Not sure whose they are right now but they were bought from a largish UK distributor. The SMT connectors I have looked at have been a lot more expensive, although of course it can save an extra production step.-- John Devereux
Me too. But the headers fit so loosely when the board is made to the manufacturer's (Molex etc.) header spec that it's a PITA to solder.
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I know but what do they do when the board is predom>
Breakaway headers...Yeah, they're also great for jumper pads, just break off the amount you need. I buy them in bulk too. Don't see myself designing for SMD headers anytime soon.
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Yeah, I always burn my finger trying to hold the header in from the other side.
John
Take a scrap of ribbon cable & a IDC connector to make a fixture to hold it up, and against the board. If there is plenty of room, all you need is the connector, and a small drill press vise to hold it.
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On a sunny day (Thu, 11 Dec 2008 17:20:40 -0800) it happened John Larkin wrote in :
I have used a piece of foam and also just some cloth on the headers. flip the board, solder the headers.
In article , snipped-for-privacy@hotmail.com says...>
We use a selective solder tool for through-hole parts. It's basically a solder fountain on an X-Y-Z stage.
What's the rough diameter of the solder "tip" of the pool? (I.e., just how "selective" is it?)
Okay thanks. Do you place thru-hole headers by hand or is a thru-hole automated PnP used? I want to spec my boards so that headers have a tight fit to make manual soldering by me easier for the time being but wondering whether this is a no-no for say an assembly house using automated PnP machines and something like the solder fountain you mention. Following say Molex's spec for the header holes results in a very loose fit and I'm wondering if there is a good reason for it.
Yes, that works but the easiest route is smaller holes allowing the headers to remain in place by themselves. IIRC, .033" holes instead of .035" does the trick for my boards. Pins are square so solder flow along and around the boards thru-hole plating is not an issue. Wondering what are the downsides associated with a tight fit.
>In article , snipped-for-privacy@yahoo.com says...>
It needs a .200" component keepout area on the reverse side, around the thru-hole components (thru-hole components can be closer to each other).
BTW, it's fun to watch. ;-)
Should also menti>
Blu-Tack.
-- John Devereux
I have seen a guy doing this with the main solder wave!
Scary - it was bad enough when I got hot melt glue on my finger.
-- John Devereux
In article , snipped-for-privacy@hotmail.com says...>
I think they're placed by hand, but I don't go back there very often. There aren't very many thru-hole parts (connectors and transformers, mainly).
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