As board densities on consumer-oriented handheld devices continue to get greater board designers are relying on the Z dimension in order to get more functionality in less space. This is being accomplished by Package on Package constructions whereby area array devices are placed on upon the next in order to marry together CPU and memory in some cases adding a co-processor to the mix. These packages tend to be high IO count, fine pitch very thin packages.
The challenges of reworking such a construction are several. Due to the thin size of the substrates these packages are prone to warping under the thermal stresses of the reflow cycle. In addition, they are difficult to inspect as their stacked nature makes it challenging to “see” via XRAY simple problems such as shorts. To add a further challenge many times these packages are underfilled meaning the removal of the device closest to the PCB has a high likelihood of being damaged upon removal.
BEST has been meeting many of these challenges to solve these issues related to POP rework by working closely with:
- Materials suppliers
- Device manufacturers
- Rework equipment suppliers
This has allowed our clients, the user community to benefit by BEST having process knowledge and experience with POP rework.
Our equipment set is up to the task. We have BGA rework systems which allow us to non contact scavenge, we have dispensing robots which allow us to dispense paste on odd-shaped land patterns typically found on one piece soldered to the board shields. Our XRAY and AOI systems are fully capable of being tools to diagnose and troubleshoot process problems. BEST can quickly build BGA reballing performs in house when devices need to be removed and replaced. We even have in house dye and pry and cross sectioning capabilities for process development.
Most importantly we have a dedicated, knowledgeable and IPC certified staff to help navigate through the various challenges of POP rework. They have been working on BGAs for 10+ years and are constantly being challenged by our clients to come up with new processes for POP rework.