Hi Steve - having the connector vacuum packaged with extent the shelf life
of the flux but its not indefinite. How long is the connector? We have seen
some issues with BGA style connectors where are warping (think of a smile
or a frown) which was causing some solder joint formation issues. What
location do the HOP defects occur?

Dave

On Fri, Aug 25, 2017 at 9:25 AM, Steven Kelly <[log in to unmask]> 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]
>
>
>
> On Thu, Aug 24, 2017 at 1:11 PM, Steven Kelly <[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
>
>
>