Precision Die Stacking for Telecom Performance

Problem:

A telecommunications customer approached Promex to develop a high-density, high-performance assembly solution. The requirement: three-die vertical stacks (same die size) with spacers between each layer, arranged in multiple stacks per ceramic substrate. To unlock performance beyond what conventional QFN packages could offer, the design demanded tight dimensional tolerances, improved thermal and electrical conductivity, and full traceability for downstream performance tracking.

Solution:

Promex engineered a turnkey solution that combined process precision with materials innovation:

• Developed a repeatable, high-accuracy stacking process using custom spacers to maintain critical die-to-die alignment across multiple stacks.
• Designed and fabricated ceramic substrates tailored for the complex layout.
• Enhanced thermal and electrical performance by incorporating diamond-impregnated die attach film (DAF) into the device structure.
• Managed the entire supply chain, from wafer procurement through final module test.
• Integrated an extensive serialization and data-tracking system, enabling full traceability from individual die to system-level performance in the field.
• Managed final electrical test, quickly and flawlessly, with results immediately downloaded to the customer’s FTP site.

Result

The customer successfully transitioned from QFN-based designs to a custom, high-efficiency module architecture. The Promex-built solution was in volume production with greater than 95% yield through the total assembly and test process, delivering measurable gains in performance, reliability, and thermal management—while giving the customer the data insights needed to continually optimize their systems.