Hello Peter,

In my previous experience we run solder pot reworks with solder 
temperature around the standard temperature used for wave soldering, 
around 260-265°C
and to improve vertical fill of hole we used to preheat the PCA with 
connector inserted in an oven or hot plate at temperature around 120-130C 
or 150C if ther are no components temperature limitation.
To reduce the problem related to the copper / other metals dissolution you 
should keep under control also the contact time of the solder alloy to the 
PCB and component pins during the rework.
 
The use of tacky flux will improve the heat transfer, reduce oxidation and 
reduce the overall rework time.
 
You may also try to use also another solder alloy that is SN100C  that in 
trials performed showed good results in terms of lower dissolution rate if 
compared with SAC305 or SAC 405.

You should also check the solder alloy contents of the solder pot, because 
of copper/metals dissolution may have changed its composition. 
 
Hope this can help you.

Regards,
Francesco
Francesco Di Maio 
IPC e Formazione
IPC A-600, IPC A-610, IPC 7711/21 Certified IPC Trainer
Via Kennedy Ingresso 2, 20871 Vimercate (MB) - Italy
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Peter Wong <[log in to unmask]> 
Sent by: TechNet <[log in to unmask]>
08/07/2014 23.34
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Subject
Re: [TN] Dissolving pins






Thanks everyone,

It's been so long for me that I forgot about SAC305 eroding metals.  I 
will get our tech to pull up the program to get more details about dwell 
times and nozzle speeds.

I believe our temperature is set that high to assist with solder fill. 
What solder pot temperatures are others running for SAC305?

Peter

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wayne Thayer
Sent: Tuesday, July 08, 2014 1:51 PM
To: [log in to unmask]
Subject: Re: [TN] Dissolving pins

Hi Peter-

SAC305 is well known for eroding metals. 325C sounds pretty darned hot to 
me! Why so high?

I have run a solder fountain rework station filled with SAC305, and it was 
very difficult to stop it from eroding the ends of the via barrels. That 
was only at 230C!

Wayne Thayer

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Peter Wong
Sent: Tuesday, July 08, 2014 4:32 PM
To: [log in to unmask]
Subject: [TN] Dissolving pins

Hi Everyone,

We ran some assemblies where after selective soldering with SAC305, the 
phosphor bronze leads on a Harwin connector look to have been dissolved.
The solder pot temperature is set at 325 deg C and we dwelled on each pin 
for no more than 3 seconds.  We are using an OA flux.  Harwin tells me 
that the melting point of the pins is 954 deg C.

We are having the solder in our selective solder pot analyzed to see if 
there is anything out of spec that could be causing this.

Has anyone else experienced something similar or does anyone have an idea 
as to what could be causing this?

A photo is available at the following link.
http://ipc-technet.groupsite.com/galleries/show/27385

Thanks
Peter


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