Why so hard to de-solder some parts?

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mzry
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Why so hard to de-solder some parts?

Postby mzry » Sun Jan 29, 2017 1:00 am

Hey all,

After doing lots and lots of upgrades / mods to my Falcon I have noticed a constant annoying thing, there is always a random part that is really difficult to de-solder. Sometimes it might be one single pin from an IC, or one side of a capacitor. What it seems like is that the solder does not melt, and it takes a LOT of heat and force to remove. Only about 5% of the board has this, but I am always scratching my head wondering why? Does anyone else know what this is?

Thx

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Re: Why so hard to de-solder some parts?

Postby rpineau » Sun Jan 29, 2017 1:46 am

This is probably happening on pins connected to the ground plane. It takes a lot more heat to keep the tin melted on these pins as most of the heat get dissipated by the ground plane copper.
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mzry
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Re: Why so hard to de-solder some parts?

Postby mzry » Sun Jan 29, 2017 5:19 am

Ah okay, that makes sense :)

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paul92706
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Re: Why so hard to de-solder some parts?

Postby paul92706 » Sun Jan 29, 2017 6:13 am

make sure you use a good Wattage Solder gun and use plenty of Flux.
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Re: Why so hard to de-solder some parts?

Postby paul92706 » Sun Jan 29, 2017 6:14 am

rpineau wrote:This is probably happening on pins connected to the ground plane. It takes a lot more heat to keep the tin melted on these pins as most of the heat get dissipated by the ground plane copper.
Rodolphe

This is true Rodolphe, i had a very hard time de-soldering the Ground pin of the NVRAM.
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Re: Why so hard to de-solder some parts?

Postby Latz » Sun Jan 29, 2017 9:07 am

Hi,
you can use a hot air gun at low heat and carefully heat up the section of the board where you want to solder. If the board (especially
the large ground planes) already has a temperature of ~50 degrees celsius it´t much easier to solder those ground pins.
Perhaps you can test the best temperature with an old defect board before you burn the Falcon ;)
Cover the other parts of the board and don´t heat it too much!

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Re: Why so hard to de-solder some parts?

Postby stimpy » Sun Jan 29, 2017 9:13 am

Latz wrote:Hi,
you can use a hot air gun at low heat and carefully heat up the section of the board where you want to solder. If the board (especially
the large ground planes) already has a temperature of ~50 degrees celsius it´t much easier to solder those ground pins.
Perhaps you can test the best temperature with an old defect board before you burn the Falcon ;)
Cover the other parts of the board and don´t heat it too much!

Latz


Solid advice and something I've used. Paint stripper gun on low heat circular motion varying the height to prevent it getting too hot. I'd say you can do more damage trying to wrestle a pin out with the solder melting as you can rip the plating from the hole or tracks leading to the hole. Practice on some old PC motherboards perhaps.
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LaceySnr
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Re: Why so hard to de-solder some parts?

Postby LaceySnr » Sun Jan 29, 2017 9:21 am

I was chatting with Atari030 about how hard and tedious it was to desolder the Falcon NVRAM chips earlier today! Big shout out to him for inviting me to his place and upgrading my STE to a 4MB monster for me :)


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