The solder wick can be rather abrasive on pads. We have found a solder
sucker (ex. PACE SX-70 SODR-X-Tractor) to clean up the pads nicely and
quickly in a controlled manor (temperature and abrasion). We are
removing and replacing Chip Scale Package BGAs using a SRT Sierra 1000
and using the PACE solder sucker to cleaning up the pads. The small
pads used for these devices made them especially susceptible to
lifting when using solder wick.
Dave Shaddock
GE

> ----------
> From:         Tom Cooper[SMTP:[log in to unmask]]
> Sent:         Wednesday, February 04, 1998 11:28 AM
> To:   [log in to unmask]
> Subject:      [TN] BGA Rework
>
>      Good morning TechNet,
>
>      We have recently started using BGA's in our prototype assembly
> lab. We
>      can successfully place and reflow the component (thermal cycle
> 1 using
>      a forced air convection oven), remove the component (thermal
> cycle 2
>      using a ChipMaster rework station + bottom heat), and place and
> reflow
>      a new component (thermal cycle 3 using the ChipMaster). Our
> problems
>      start when we try a 4th thermal cycle to remove the component
> again.
>      We are lifting pads during the site preparation using a thin
> solder
>      wick. Is there a limit to the # of thermal cycles on BGA land
> patterns
>      or are we doing something wrong?. Is solder wick appropriate
> for
>      leveling solder?  Are there repair kits available to fix lifted
> pads?
>      Our boards are FR4 W/ 1/2 oz. copper. We are using a mix of
> PBGA's and
>      TBGA's. The TBGA's (which require a little more heat for a
> longer
>      duration) seem to be lifting the pads more readily.
>                                 All comments would be greatly
> appreciated,
>                                         [log in to unmask]
>
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