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 Post subject: Tin wiskers
PostPosted: July 13th, 2018, 8:47 am 
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Joined: February 28th, 2013, 3:31 pm
Posts: 859
Be careful of lead free solder. Check out the link:

https://www.microcontrollertips.com/whe ... A0MDY0MgS2


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 Post subject: Re: Tin wiskers
PostPosted: July 13th, 2018, 9:33 am 
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Joined: July 24th, 2015, 4:17 pm
Posts: 650
Location: Parkville, Maryland
tomp wrote:
Be careful of lead free solder. Check out the link:

https://www.microcontrollertips.com/whe ... A0MDY0MgS2



WOW!! Who knew? I use Eutectic solder -- 63/37 -- Tin/Lead. I've tried silver-bearing solders in the past but I found that Eutectic solder "sounds better."

It's also easier to use with a lower melt temperature which is important with solid-state stuff as you don't linger to get a good joint -- I.C.s especially are not damaged from heat.

One final note -- soldering is not gluing. It is an alloying process. I worked with a guy that had worked at G.E. many decades ago that before he could be certified to work on electronics he had to attend soldering training -- a six week course!! WTF?!! Six weeks? That shows the importance of doing it right.

Now lets think in terms of other contact situations that have tin-plated pins. Hmmm. Food for thought.

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Walt


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 Post subject: Re: Tin wiskers
PostPosted: July 13th, 2018, 10:16 am 
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Joined: July 17th, 2016, 6:24 am
Posts: 406
SoundMods wrote:


One final note -- soldering is not gluing. It is an alloying process.


Not true.
Solder is an alloy but soldering is not "alloying" (presuming you mean creation of an alloy).

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 Post subject: Re: Tin wiskers
PostPosted: July 13th, 2018, 11:03 am 
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Joined: January 15th, 2015, 7:19 am
Posts: 592
Location: Baltimore MD
do not go there Shashi


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 Post subject: Re: Tin wiskers
PostPosted: July 13th, 2018, 12:10 pm 
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Joined: July 24th, 2015, 4:17 pm
Posts: 650
Location: Parkville, Maryland
Pelliott321 wrote:
do not go there Shashi


Good advice!

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Walt


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 Post subject: Re: Tin wiskers
PostPosted: July 13th, 2018, 12:49 pm 
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Joined: February 28th, 2013, 3:31 pm
Posts: 859
One of the most important things when soldering is to have a good mechanical joint before applying solder. With few exceptions such as surface mount devices you should think of the solder as a conductive filler for good current flow and not a support mechanism. Also, if the surfaces are not clean your chances of getting a good joint are pretty much nil.


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 Post subject: Re: Tin wiskers
PostPosted: July 13th, 2018, 1:31 pm 
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Joined: July 24th, 2015, 4:17 pm
Posts: 650
Location: Parkville, Maryland
tomp wrote:
One of the most important things when soldering is to have a good mechanical joint before applying solder. With few exceptions such as surface mount devices you should think of the solder as a conductive filler for good current flow and not a support mechanism. Also, if the surfaces are not clean your chances of getting a good joint are pretty much nil.



Good advice to say the least. Before soldering insert-type parts be sure to clean the leads so there is no surface oxidation left. Even new parts should be prepared.

Empty PC boards should be cleaned before use to assure good solder connections. Reusing PC boards as when making changes or modifications it's import to clean off all flux residue before installing new parts. My favorite chemical is a good flux cleaner. I've included a link for one example:

https://www.circuitspecialists.com/4140 ... gI_iPD_BwE

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 Post subject: Re: Tin wiskers
PostPosted: July 13th, 2018, 1:38 pm 
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Joined: July 8th, 2016, 4:34 pm
Posts: 203
To truly enjoy soldering you should have assembled a Heathkit color tv kit from the late 1960's (solid state but discreet parts). I did.


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 Post subject: Re: Tin wiskers
PostPosted: July 13th, 2018, 1:51 pm 
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Joined: February 28th, 2013, 3:31 pm
Posts: 859
SoundMods wrote:
tomp wrote:
One of the most important things when soldering is to have a good mechanical joint before applying solder. With few exceptions such as surface mount devices you should think of the solder as a conductive filler for good current flow and not a support mechanism. Also, if the surfaces are not clean your chances of getting a good joint are pretty much nil.



Good advice to say the least. Before soldering insert-type parts be sure to clean the leads so there is no surface oxidation left. Even new parts should be prepared.

Empty PC boards should be cleaned before use to assure good solder connections. Reusing PC boards as when making changes or modifications it's import to clean off all flux residue before installing new parts. My favorite chemical is a good flux cleaner. I've included a link for one example:

https://www.circuitspecialists.com/4140 ... gI_iPD_BwE


Looks like good stuff. I still have some Trichloroethane which you can't get anymore but when I run out I'll order some of this.


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 Post subject: Re: Tin wiskers
PostPosted: July 13th, 2018, 4:06 pm 
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Joined: December 14th, 2013, 2:19 pm
Posts: 530
tomp wrote:
One of the most important things when soldering is to have a good mechanical joint before applying solder. With few exceptions such as surface mount devices you should think of the solder as a conductive filler for good current flow and not a support mechanism. Also, if the surfaces are not clean your chances of getting a good joint are pretty much nil.


All true about cleaning surfaces prior to soldering, not using solder as mechanical support when possible.

To avoid using solder as a "support mechanism" AND to improve conductivity by NOT relying on solder to be the conductive path, wrap leads around turret posts, lugs, other component leads, etc. as tight as practical, and when on a lug/post, ensure there is adequate lead-to-lead contact; i. e. do not let the post be the mechanism that interconnects multiple flying leads. Ensure that the solder fills the gaps between leads, and does not merely bridge the gap.

Also, on PCBs, leads are usually much smaller than the hole. Push the component lead through the hole, then bend 90 degrees so that the lead lays flat against the PCB conductive surface, then bend 90 degrees again, so the lead is again perpendicular to the hole, but offset from it. This provides some component mechanical support and does not rely on solder to bridge the hole between the PCB and lead.

You smart guys already knew that though!

Thanks for the reminder about the eutectic solder! All I have left is 1/2 a bar of Cardas for use in the solder pot.

Stuart


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