Improved Results in R&D

Yacov Duszly – Research Engineer – Western Digital Sandisk

IC Removal from underneath avoids a reflow cycle on the IC, allowing the same BGA to be used on the original PCB.
Air knife removes old solder with no reflow or operator error in a controlled ‘no touch’ process.
BGA is reballed using a laser – no reflow
The interposer PCB can be fitted with columns instead of spheres to increase stand-off height and lift assemblies above adjacent components.
Retronix has various mechanical and electrical tests available for both individual ICs and PCBs to verify operation.

The BGA to be tested is cut from a PCB. Then the remaining PCB base material is milled from the BGA.
The remaining solder is removed using braid and a soldering iron – this is to avoid heat cycles damaging either the software or the hardware of the BGA.
On an identical PCB the same BGA is removed using hot air, and discarded. This PCB then becomes the host for the experiment.
It is preferable to use the BGA on the original PCB but this is too risky due to multiple heat cycles.
2 Grypper sockets (in blue) are then soldered to the main PCB and the interposer PCB.
The interposer PCB has spheres attached to the bottom side so it fits in the bottom gripper socket.
Then the whole thing comes together to make the top BGA connect with the PCB.
This however has 2 mechanical and 2 solder connections, which could cause a loss of signal.
Also the BGA and PCB have had 2 full reflow cycles.

BGA removed from original PCB using heat from underneath. This is not a reflow cycle so BGA not compromised.
This allows the original BGA to be used on the original PCB, which is preferred.
Remaining solder removed using an air knife with no abrasion.
BGA reballed using laser pulse creating zero heat.
Solder Columns attached to the interposer PCB to increase height stand off
BGA soldered to interposer PCB using low temperature solder, no reflow cycle. Interposer PCB soldered to original PCB using the same process.
Connection achieved using no gripper sockets or mechanical connections, only solder connections so signal integrity much better.
No reflow cycles used in entire process.

For more information contact :