Adapting Substrate Design for Large Die Assembly

Substrate Design for Large Die Sizes

At Intech Technologies, we recently undertook a project that presented a unique set of challenges in our R&D packaging efforts. The task was to develop a packaging solution for a 32 I/O count Ball Grid Array (BGA), with the complication arising from the size of the die, which was 12mm x 14mm. This size exceeded the capacity of our available package options, as none had a die attach pad area large enough to accommodate it.

As we explored potential solutions, our focus shifted to finding a suitable Printed Circuit Board (PCB) substrate. This phase introduced its own set of problems. The BGA’s assembly process involves die attach, wire bonding, and encapsulation, each with specific requirements. One critical issue was the heating process for wire bonding, which is typically done around 150°C. This temperature was incompatible with the BGA’s requirements for even heat distribution during the process. Furthermore, our encapsulation materials, LOCTITE ECCOBOND FP4450LV and HYSOL® FP4450 Liquid Encapsulant, had a maximum operating temperature of 150°C, further complicating the process.

The sequence of assembly also posed a dilemma. Balling the PCB substrate before die attachment, wire bonding, and encapsulation was impractical due to the temperature constraints. Conversely, completing the wire bonding and encapsulation before reballing wasn’t viable, as our molding compound wasn’t suitable for high-temperature exposure. An alternate approach of balling the substrate without encapsulation was considered but dismissed due to the risk of damaging the units and the limited availability of dies.

To address these challenges, we developed a two-layer PCB design. The first layer was designated for the die attach pad, and the second layer was designed for the BGA grid. We conducted the assembly work and the balling job separately for each layer. Both layers featured through-holes at their edges, and after completing all processes, we used gold (Au) pins to connect the two boards, forming the final substrate.

This approach successfully addressed the unique challenges we faced in this project. At Intech Technologies, our focus is on finding practical solutions to complex problems, ensuring that our clients receive products that meet their needs while adhering to the highest standards of quality and reliability.

R&D Challenges: Adapting Substrate Design for Large

Assembled BGA Type PCB Substrate with plastic cap ready to Ship


BGA on the second PCB

Fully Assembled BGA Type PCB Substrate with Die with a transparent plastic cap

R&D Substrate

PCB Layer 1 Top surface with extra large die attach area

Substate Design for Large Die

PCB layer 2 with Balled ball grid array

Top view – Die attach pad


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