Hi Dave,
Thanks for pointing me to the paper. I took the temperature of the solder at the nozzle and discovered that it was at 315 deg C for the 325 deg C pot setting. We definitely will look at reducing the temperature of our solder at point of contact and reduce dwell times.
Is 300 deg C a good starting point or should we go lower?
Thanks again,
Peter
From: David Hillman [mailto:[log in to unmask]]
Sent: Wednesday, July 09, 2014 9:39 AM
To: TechNet E-Mail Forum; Peter Wong
Subject: Re: [TN] Dissolving pins
Hi Peter - the dissolution of copper is a function of solder alloy, dwell time, and temperature so changing the preheat temperature isn't going to have a huge impact. As other have detailed, other lead-free solder alloys have lower dissolution rates that may give you some advantage. And if changing solder alloys is not an option, using a lower solder pot temperature will reduce the copper dissolution rate for a given dwell time. I looked up some old data for a SAC alloy/300C temperature and we had a dissolution rate of 5 mm3/sec and at 325C the rate would be even higher. One good published paper to go look at is the National Physics Laboratory (NPL) report MAT 26 Measurement of Copper Dissolution of Leadfree Solder Alloys, November, 2008. Good Luck.
Dave
Dave
On Wed, Jul 9, 2014 at 10:15 AM, Peter Wong <[log in to unmask]<mailto:[log in to unmask]>> wrote:
Good morning,
After looking at our program, I've discovered that there are 4 locations along the length of this connector where we are actually dwelling for 4 seconds and moving along at 3 mm/sec. The dissolved pins seem to follow the pattern of where we stop and dwell for those 4 seconds.
Thanks to everyone for the suggestions. I think we need to preheat the boards in a different manner versus how we are doing it now.
Thanks again for your insights.
Peter
-----Original Message-----
From: Peter Wong
Sent: Tuesday, July 08, 2014 2:35 PM
To: [log in to unmask]<mailto:[log in to unmask]>; 'Wayne Thayer'
Subject: RE: 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]<mailto:[log in to unmask]>] On Behalf Of Wayne Thayer
Sent: Tuesday, July 08, 2014 1:51 PM
To: [log in to unmask]<mailto:[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]<mailto:[log in to unmask]>] On Behalf Of Peter Wong
Sent: Tuesday, July 08, 2014 4:32 PM
To: [log in to unmask]<mailto:[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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