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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Patrick Ng

#16420

Gold plated components - solderability issue | 30 March, 1998

Hi, We have encountered de-wetting issues with gold plated components( SMT LEDs ). The problem comes and go and we yet to locate the root cause ( process, component or solder paste etc ). The rest of the components on the boards are not having this problem. Would like to hear from you if you have similiar encounters! Thks, Patrick

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Earl Moon

#16422

Re: Gold plated components - solderability issue | 30 March, 1998

| Hi, | We have encountered de-wetting issues with gold plated components( SMT LEDs ). | The problem comes and go and we yet to locate the root cause ( process, component or solder paste etc ). | The rest of the components on the boards are not having this problem. | Would like to hear from you if you have similiar encounters! | Thks, | Patrick Again, this is an old issue. It was resolved in the military/aerospace community many years ago when all devices were gold plated to prevent oxidation and non wetting. As always, the answer is to get the gold off the leads or chip device solder termination areas before soldering. This is done using a constantly "pure" solder dip. This process replaces the gold, as it is "leached" out into the solder pot, with the solder medium of choice. Care must be taken to ensure solder purity as gold will contaminate the solder as it would during wave soldering operations. As you know, initial solder joint quality is unacceptable using gold leads - initially. The biggest problem is solder joint embrittlement later on as fractures occcur. A good answer to gold and tin immeresion parts used to be tin/lead plated and reflowed solder termination areas. Solderability was excellent using this technology as oxidation and other contamination was minimal and solder wetting was excellent as was long term reliability. You will have this again when you solder dip your gold leads thus effecting the same effect and solder joint quality though the expense and time is significant. Earl Moon

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Justin Medernach

#16421

Re: Gold plated components - solderability issue | 30 March, 1998

| Hi, | We have encountered de-wetting issues with gold plated components( SMT LEDs ). | The problem comes and go and we yet to locate the root cause ( process, component or solder paste etc ). | The rest of the components on the boards are not having this problem. | Would like to hear from you if you have similiar encounters! | Thks, | Patrick Patrick, Talk to your paste vendor about your problem. See if they have a more aggressive flux formulation. Also, component / assy. permitting, jump up your reflow temp by 10 or 15 degrees Celcius and you will see a significant improvement in wetting and solder joint appearence. Remember, gold turns the joints dull. Too much gold will cause fracture. Regards, Justin Medernach Flextronics Int'l PIC East

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