Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.




solderability | 11 October, 2002


I was wondering if anybody has some useful advice with regards to achieving 100% solder penetration on one pin of a through hole device which I believe is attached to a ground plane. All other pins on the through hole device are fine, Just this one pin where I am struggling to get the desired result. The device is hand-soldered, and adding extra pre-heat and flux doesn't seem to help. The pin to hole ratio is pretty good and the device has a tin/lead finish.

Thanks in advance

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solderability | 11 October, 2002

Designers love to do BIG copper pours for several reasons: * Maximize heat spreading. * Increase EMI shielding. * Laziness.

The poor folk that solder the parts on boards HATE big copper planes near solder pads. During soldering, fat copper traces [or direct connection to the plane] suck away the heat that is supposed to melt the solder to form the electrical joints. So boards have lots of opens, partially-formed, or intermittent solder joints. Solutions available to these folk are hazardous: * Dialing-up the heat in the soldering machine to overcome this heat-sinking effect can damage the board or components. * Doing post-machine rework can damage the copper plating on the though hole wall, because it is very easy to overheat a solder connection that doesn�t solder well.

Your board designer needs to give you thermal relief on the pins that are giving you fits.

Thermal Relief. [1] Disconnecting the solder pads from the copper in the board ground plane, as much as possible, using the thinnest possible traces that will carry the electric current. [2] A wagon wheel-shaped relief pad etched in the copper of a ground plain around a through hole. Without the thermal relief, the plane robs the component pad and component lead from the heat required to fully fill the solder joint.

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solderability | 11 October, 2002

For whatever its worth,

IPC does not require a full fillet in this situation.

If it has to be a complete fillet due to contractual agreements you may want to try and preheat the board first with hot air or something and then solder.


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solderability | 17 October, 2002

I agree with everything stated thus far. However, what soldering iron are you using. You may be able to solder the pin with an iron that delivers continuous heat and if there is room utilize a large tip as a heat reservoir. What happens is that the iron will deliver enough heat to the joint before it dissipates to the heat sink allowing for a good intermetallic bond. "Hopefully". Sometimes it works, sometimes it doesnt. It most likely is a quicker fix for the boards you currently have rather than waiting for a board fix.

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