Resistor orientation

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Resistor orientation

Postby Bruno2000 » Sat Feb 16, 2008 12:34 pm

I have noticed that in most DIY projects, the resistors are mounted horizontally on the board, usually taking up 0.1” x 0.5” of board real estate. Is there a specific reason for not mounting them vertically (and only taking up a 0.1” x 0.2” space)?
Thanks for your input!
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Re: Resistor orientation

Postby mediatechnology » Sat Feb 16, 2008 12:43 pm

I think vertical mounting became a big "no-no" back when people were actually auto-inserting through-hole parts. (I guess they still do.) For DIY as you point out it doesn't really matter. There sure are a lot of vertical parts being stuffed into 990 and 2520 modules. Most of the Vectorboards I build are vertical mount Rs. No reason in particular that I'm aware of other than the component libraries are that way and we hope to mass-produce our products someday.

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Re: Resistor orientation

Postby mediatechnology » Sat Feb 16, 2008 3:14 pm

One other point is that discrete op amps are always potted except for home made units. I doubt John Hardy would consider using vertical mounting if the product were not to be potted.


Good points all Roger. WRT the above I think another reason for potting is to aid thermal equilibrium between devices and reduce gradients. Although we frequently see potting to keep things top secret that's certainly not the case with the 990.

Now that you mention it I do recall the reliability concerns expressed by my MicMix boss, John Saul, who came from a military contractor background. All our stuff was hand assembled but he still banned it.
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Re: Resistor orientation

Postby Bruno2000 » Mon Feb 18, 2008 10:01 am

Thanks guys,
Nice to have your thoughts! Most of the stuff I build ends up in a remote truck, so making things small is a plus. Even with a lot of bouncing down the road, I have yet to have a mechanical failure of a vertically mounted resistor, and I’ve been bouncing down the road for a number of years. I am considering trying some LARGE (so I can see them) surface mount resistors. I’ll let you know how that turns out. What does fail are TO-220 package leads. Just can’t take the vibration.
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Re: Resistor orientation

Postby mediatechnology » Mon Feb 18, 2008 10:24 am

What does fail are TO-220 package leads. Just can’t take the vibration.


Curious - Where do they fail? Inside the package or lead-to-board connections? Is it with a big heat sink as mechanical load problem?

There's a lot to be said for flying leads to power devices.
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Re: Resistor orientation

Postby Bruno2000 » Tue Feb 19, 2008 10:25 am

They fail inside the package. When you un-solder them from the board, the lead just falls out of the package. The device is attached to the side of a chassis, and soldered to a board that is mounted to the same chassis, so there is no mechanical heatsink "load" on the device. I now modify all new gear with an inch or so of stranded wire in a loop, and have not had further problems.
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Re: Resistor orientation

Postby mediatechnology » Mon Mar 06, 2017 9:03 am

This thread is a popular link from stackexchange. http://electronics.stackexchange.com/qu ... -resistors
Thanks for visiting the Pro Audio Design Forum!


While scanning "Avoiding Passive-Component Pitfalls," Doug Grant, Scott Wurcer, Analog Dialog, 17-2, 1983 I found the following figure.

http://www.proaudiodesignforum.com/imag ... 2_1983.pdf

Resistors mounted vertically to conserve board space.
Thermal gradients create significant thermoelectric circuit errors.


Image
"Avoiding Passive-Component Pitfalls," Doug Grant, Scott Wurcer, Analog Dialog, 17-2, 1983

Finally we have the answer to this nagging question.
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