Hi Bob - we did a paper on the shelf life of cored wire solder and we
consider it "unlimited". A cored wire is basically a hermetically sealed
chamber so the flux core really can't degrade due to moisture or oxygen
interactions. I took a 20 year old spool and it tested as good as a 5 year
old spool. I'll send you the paper. If other folks would like the paper,
just send me an email off line so we don't clog up the Forum.

Dave

On Fri, Aug 25, 2017 at 9:47 AM, rkondner <[log in to unmask]> wrote:

> Question about Flux Life:
>
> I have some roll solder on my work bench which is probably 20+ yeas old.
> Still smokes and seems to solder fine. Of course this fux is inside the
> solder core.
>
> Many chemicals are long lived (table salt for example) and some are short
> lived.
>
> Does anyone know what it is in solder that "Goes Bad"? I admit I am a
> "Date Code Skeptic".
>
> Bob K.
>
>
> On 8/25/2017 10:25 AM, Steven Kelly wrote:
>
>> Hi Dave,
>> The parts come vacuum sealed and after opening we have a fairly short
>> period of time to assemble. Manufacturer also said the “dull ball” on the
>> connector is common for lead-free solder ( agree) and is not considered
>> related to the failure. Its’ mainly because tin constituent appears on the
>> surface. ( I understand that)
>> Then they say the “residue” which we identified on the ball is considered
>> to be flux and is not related to the head in pillow.
>> But only a few of the 200 or so balls exhibit this issue and I am not
>> saying we do not have other issues but we have traced some of the head in
>> pillow to a couple of the so-called flux residue balls . On average we are
>> getting 1-3 failures per 200 joints.
>> We have measured the flatness of the rigid stiffener – looks OK to us –
>> co-planarity is .002- .004 after convection reflow.
>> Reviewing what Bev said yesterday- pasting – we looked at it 3 times but
>> doing it again.
>> I also have pictures of what we call an incomplete ball which I would
>> like to post but I need a refresher course on how to do this.
>>
>> Thanks for everyone’s help.
>> Steve Kelly
>>
>> From: David Hillman [mailto:[log in to unmask]]
>> Sent: August-25-17 10:06 AM
>> To: TechNet E-Mail Forum <[log in to unmask]>; Steven Kelly <
>> [log in to unmask]>
>> Subject: Re: [TN] Dried flux
>>
>> Hi Steve - We use a number of "bga style" connectors where there is a
>> solder charge/preform on the connector which is designed to combine with
>> the solder paste deposit creating sufficient solder volume and good solder
>> joint integrity. I am not familiar with the having these types of
>> connectors with "dried flux" - flux has a shelf life so the manufacturer's
>> comment doesn't make much sense. From a practical point, the flux in the
>> solder paste deposit is doing the bulk of the oxide scrubbing action so
>> dried flux contribution is most likely a moot point. But - the fact that
>> the manufacturer did not acknowledge the possible shelf life issue is
>> dis-concerning.
>>
>> Dave Hillman
>> Rockwell Collins
>> [log in to unmask]<mailto:david.hillman@rockw
>> ellcollins.com>
>>
>> On Thu, Aug 24, 2017 at 1:11 PM, Steven Kelly <[log in to unmask]<mailto:
>> [log in to unmask]>> wrote:
>> Hi All,
>> I have a new hi-density BGA connector I am trying to assemble. When the
>> supplier makes the connector they "solder balls onto the pin" (lead free).
>> We see dried flux on the balls and when we solder the connector we are
>> getting a few joints with head in pillow. The connector manufacturer says
>> the dried flux is not an issue - is this true? Thanks. Steve Kelly
>>
>>