pucho812

Smd pads with Through-Hole parts
« on: July 01, 2018, 04:23:32 PM »
Wasn't sure where to post this...
I've heard NASA spec is to use Through-Hole parts but single sided boards and smd pads. 
Can anyone confirm this?
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.


JohnRoberts

Re: Smd pads with Through-Hole parts
« Reply #1 on: July 01, 2018, 04:39:19 PM »
Last century Peavey mixed SMD on the solder side with TH parts on single sided PCB...  It was very cost effective for mixers and the like.

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

Re: Smd pads with Through-Hole parts
« Reply #2 on: July 01, 2018, 04:39:54 PM »
Sounds like a nice story, but it makes little sense. "I keep pushing, but the parts don't go into the board" LOL. NASA isn't one thing (or one place either),  so while someone somewhere at NASA may have done this, the likely horrible reliability for such an assembly would heavily discourage these sorts of hacks, especially for anything going into space.

Surface mount is hard enough to get it to work reliably even with a specific footprint for each part, with fairly precise and repeatable component dimensions, so the vagaries of hand bent leads seems to be asking for certain disaster. And, through-hole parts are on the way out anyway.

You can mix through hole and SMD on a board with no problems at all, and I find it useful for the few instances where SMD parts can be problematic, such as for electrolytic caps, and film caps with nice dielectrics. Maybe this was what was being referred to?

pucho812

Re: Smd pads with Through-Hole parts
« Reply #3 on: July 01, 2018, 04:59:33 PM »
Yes you can mix smd and through hole.  Was done at my last gig no problem. We also at times used through hole parts on smd pads during repairs due to availability of parts.

Forget NASA so much as aerospace using through hole parts to smd pads.  Almost like melf resistors but they are through/hole.
« Last Edit: July 01, 2018, 05:09:46 PM by pucho812 »
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.

pucho812

Re: Smd pads with Through-Hole parts
« Reply #4 on: July 01, 2018, 05:10:30 PM »
I'll get my buddy at Boeing to  get some examples
« Last Edit: July 01, 2018, 05:56:48 PM by pucho812 »
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.

JohnRoberts

Re: Smd pads with Through-Hole parts
« Reply #5 on: July 01, 2018, 05:46:20 PM »
Yes you can mix smd and through hole.  Was done at my last gig no problem. We also at times used through hole parts on smd pads during repairs due to availability of parts.

Forget NASA so much as aerospace using through hole parts to smd pads.  Almost like melf resistors but they are through/hole.
Aerospace was big on packaging density, for reduced size and weight (i.e. payload).  Back in the 60's I worked on some navy stuff, and in the early 70s after getting out of the army on some missile guidance stuff. Back then they used what was called "cord wood" where thru hole parts would be sandwiched between two stacked PCB... You think modern stuff is hard to troubleshoot, try that.   ::)


JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

john12ax7

Re: Smd pads with Through-Hole parts
« Reply #6 on: July 01, 2018, 05:48:02 PM »
Why would you want to do this? Through hole has mechanical strength.  SMD parts are small and light so solder is enough to hold reliably.

pucho812

Re: Smd pads with Through-Hole parts
« Reply #7 on: July 01, 2018, 05:57:48 PM »
Why would you want to do this? Through hole has mechanical strength.  SMD parts are small and light so solder is enough to hold reliably.
I think it has to do with what's easier to get a hold off part wise.
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.

JohnRoberts

Re: Smd pads with Through-Hole parts
« Reply #8 on: July 01, 2018, 08:47:56 PM »
I think it has to do with what's easier to get a hold off part wise.
Back in the early days of SMD (like last century) parts unavailability in SMD packages was a common problem. These days hopefully not so much.

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

mjrippe

Re: Smd pads with Through-Hole parts
« Reply #9 on: July 02, 2018, 11:45:05 AM »
If you want to know how to DIY with NASA quality, check out their workmanship standards document:
https://workmanship.nasa.gov/lib/insp/2%20books/frameset.html


pucho812

Re: Smd pads with Through-Hole parts
« Reply #10 on: July 02, 2018, 05:59:06 PM »
I do have their soldering guide.  but your link is great thanks
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.

pucho812

Re: Smd pads with Through-Hole parts
« Reply #11 on: July 19, 2018, 01:17:03 PM »
Was informed this is due to board flexing from high temps in aero space.
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.


 

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