Use of Linear Technologies LTC1733| 6 January, 2004
Dear Colleagues, I am evaluating the Linear Tech. Corp. LTC1733 MSE Package for use in our SMT Dept.. For this application I will need to consider the possibility that we will be required to repair these devices after some time in the field. My problem is that the package has a large heat sink directly on the bottom of the part.
Two questions come to mind. - How do we re-work/replace this package? Specifically, how do I re-solder the heat sink under the part? - How do I inspect the heat sink solder joint after initial soldering? (we do not currently have X-ray capability)
Use of Linear Technologies LTC1733| 7 January, 2004
Her is how we rework these typew of components.
First remove the device using hot air. It is sometimes helpful to heat the back of the board if possible to get the thermal pad heated with less strain on adjacent comps.
Remove the remaining solder from the lead and thermal pads on the board.
Apply solder to the thermal pad.
Set the new component down on the pad and determine if you have provided sufficient or excess solder to the pad. The part should rock back and forth on the thermal pad solder bump. This will verify that you are making contact with the added solder.
Remove the part from the pad and heat the thermal pad with hot air until the solder melts and place the new part on the pads re-apply heat for a few seconds to ensure that the solder wets to the part and let cool. If the part is stuck you have soldered the thermal pad.