|Ask the Experts|
January 21, 2021
We need to perform some Package-on-Package (PoP) rework. The only package we need to rework is the top package. Can we rework the top package only, or should we remove both packages and then replace them both?
|Expert Panel Responses|
Yes you can rework only the top package. It can easily be removed with a combination vacuum cup (for removal) and hot gas solder nozzle (for reflow). In fact, if you have more than one layer, you can remove the layers one at a time.
Our Martin Expert 10.6 Rework System can do it hands free. Please visit www.bgarework.com for more information on our Rework Equipment or call me at 603-627-8989 to discuss our solution in more detail.
Sales Manager - Martin Products
Yes the top package (memory) for a PoP device can be removed separately from the bottom. To be successful with this process, precise control over the thermal profile is critical and the use of nitrogen is very helpful. Once removed, the site is prepared and a new top package is soldered on.
Keep in mind you are putting the bottom device through 4 thermal cycles. As long as it can handle this, it is very possible to be successful in this type of rework.
Finetech has worked with several companies, like Texas Instruments to help develop their PoP rework process. For more information please visit www.finetechusa.comor give us a call at 480-893-1630.
It is possible to rework the top component of a PoP stack. Care must be taken to prevent damage to the solder joints in the lower component(s).
During removal of the top component it is extremely important to avoid putting any downward or lateral force on the stack. Some people will apply corner glue to the lower component to help prevent displacement during the removal process. An automated rework system with a Zero Force removal capability will eliminate this extra step.
After removal of the top component the intermediate pads must be cleaned to prepare for the subsequent replacement step. A non-contact solder removal is required. The small pitch used with PoP devices, and the common tight perimeter pattern will likely require automation to achieve consistent results.
Solder paste is general not used during the upper component re-attach. We recommend a flux dip using a simple flux well and no clean flux. Placement of the upper component is done prior to heating, so displacement of the lower component is not an issue.
VJ Technologies, Inc.
This would all depend upon the skills of the technician doing the work. The other element I would consider is the testing of that particular component due to the rework performed.
Product Engineering should decide if the POP needs to be tested separately or can it be tested within the circuit of the product. Once this decision is made then the appropriate rework can place of rework can be defined.
Vice President, Technical Director
The rework of POP devices with our micro oven tweezers nozzles has been very successful for many companies for many years. These nozzles can be fitted onto the APR-XLS system or the Scorpion rework system which features auto profiling. Either system can be programmed to remove either the top or the entire POP or a particular layer in multi-POP devices or stacked devices.
Keep in mind you will subject the bottom component to multiple rework cycles and operator skill is required for site dressing the section that remains on the PCB.
Regional Sales Manager
OK International Inc.
This is a very delicate process. Precise control of the temperature profile is needed to allow the removal of the top package without disturbing the bottom package. The use of shims and or staking the bottom BGA package could help to prevent shifting or creating soldering defects such as shorts or opens during the rework process.
Circuit Technology Center
|Submit A Comment|
Free Newsletter Subscription
Circuitnet is built for professionals who bear the responsibility of looking ahead, imagining the future, and preparing for it.
Insert Your Email Address