Jason - I agree that it appears that the airflow is the problem. Of greater
concern is that you probably have damaged the part (if you wanted to reuse
it) due to moisture absorption and then expansion under the higher temps of
the rework system. You may want to consider baking the moisture out of the
PC Board Assembly, especially the BGA, if you need to make a standard rework
procedure for the BGA on that board assembly. In addition, you still need to
verify from a reliability viewpoint that no damage was done. Ideally, your
situation is easier to resolve with a larger nozzle and the bakeout.
Ed Valentine
Electronics Manufacturing Solutions
8612 Mourning Dove Road, Raleigh, NC 27615
Phone: (919) 270-5145, Fax: (919) 847-9971
Email: [log in to unmask]
Website: http://www.ems-consulting.com
----- Original Message -----
From: Jason Gregory <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, July 12, 2000 5:18 PM
Subject: [TN] BGA Reflow Problems
> Hello technetters,
>
> I'm having a strange problem at my new digs. We have an outer-arrayed 256
> pin BGA going on a 6 layer FR-4 board. Everything is standard. The problem
> is the rework. We have a Conceptronic station and the nozzle we are using
> does not fully encapsulate the component. It always stays about 1/8" off
the
> board. Therefore, I am not getting full underside airflow. The techs are
> using extremely high temperatures to get the component to reflow. I am
> wondering this: if I run a standard profile (using previous BGA reflow
> experience) and the part won't even begin to reflow, can I chalk it up to
> the airflow problem. I am guessing that the reason that using abnormally
> high temps is reflowing the part, then it's only happening by conduction
> through the part, not proper heat getting under it. Also, in this regard,
if
> I'm only reflowing by conduction through the part, then what's happening
to
> the integrity of the part? Please help.
>
> Jason Gregory
> ACT Manufacturing-Production Supervisor
> Corinth, MS.
> (662)287-3771 x470
> [log in to unmask]
>
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