Reminder of solder mechanical properties
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chillysalsa

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Solder is a temperature that will undergo creep at room temperature. This is a process that is active whenever a mechanical stress is imposed typically at temperatures 0.4 of the melting point.

For solder, room temperature corresponds to about 0.65 of it's melting point (455ºK) on the Kelvin scale, which is why creep behavior is a consideration.

Even when the stress or loading is small, solder may easily deform over time. This can lead to solder joints failing over time. This is why it is advised that through-hole components be mechanically clinched and why connections to wiring should be looped, for example like those on hooked or eyelet terminals:


From the NASA soldering specs, click more examples.

Sidenote: Surface mount components are unique in that only the solder is holding them onto the board and supporting the loads, and thus these components must be small and designed to prevent differences in thermal expansion to cause stress that will shorten component life.

Just something people shoulder remember from a workmanship standpoint. I recall taking the J-standard soldering coarse at an aerospace company, and some people's concerns about proper assembly and workmanship.
 
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nikongod

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i forget who it is, but ther is/was a builder here who bends every resistor leed/chip/socket pin fush with the board before soldering.

it sounds like a good idea if you NEVER want the thing coming apart ever. probably impossible to make component value changes at a later date though.
 
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guzzler

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In all fairness, there is very little stress on the components on a PCB board in normal use. It may be good practice (and easier to solder) on loose connections, but if you think that the only real way to apply a force to a component mounted flush to a board is to put a tip underneath it and lever it up, it's not a big deal. Fair enough for space ships, but not for desk bound amplifiers!

g
 
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chillysalsa

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On circuit board components I would agree that it is not a big deal. But for things like wiring, power cables, interconnects, it would be wise to build it with some mechanical reinforcement.
 
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mono

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I agree but usually take it one step further- not only the "J" in the picture but also cinching that J tight against the wire before soldering. However, that makes it almost manditory to cut the joint if it ever needs be undone, it can't so easily be desoldered enough later.
 
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arspy87

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I was thinking, when soldering interconnects and whatnot, would it help reinforce the joint if it were covered with a layer of hot glue or epoxy?
 
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skyskraper

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i shore up some connections with hot glue, a lot of interconnects where the wires are significantly smaller then the actual connectors, i fill up with hot glue to give a bit of strain relief.
 
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SiBurning

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Thanks for the NASA page. Never can have too much technique.

There used to be competing wiring guidelines from AT&T and some other company. I always knotted wires together sorta Ma Bell style before soldering them. For boards, I always crimped component leads by hand to match what a crimping machine would do. Used a pair of needlenose, a heavy dip socket, and some other home made jigs on a wood board--nail down a couple of rollers. The backend of some needlenoses are perfect for forming the shape. For one thing, comnponents stayed on the board when I turned it over to solder. And most smaller components can be crimped so they have some taughtness and don't move when you solder. Others sort of dangle, but at least they don't fall off.
 
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