Manufacturing Readiness of BVA(TM) Technology for Fine-Pitch Package-on-Package

Package-on-Package (PoP) has become common for packaging the processor and memory subunit in today's smartphones and tablets. Today's PoPs provide only about 300 interconnects between the base and top packages due to physical limitations posed by existing manufacturing methods. As a result, memory data bandwidth is limited to 25.6 GB/s at 1600 MHz DDR signal speeds. With a trend towards System-on-Chip (SoC) mobile processors with multi-core CPU, memory bandwidth requirements are sharply increasing. To meet these needs, a wide IO memory industry standard has emerged to specify 512 memory data interconnects. This standard provides about 4 times current bandwidths (>100 GB/s) even at lower 800 MHz DDR signal speeds. For memory devices to offer 512 data lines, a total of about 1000 interconnects are needed to include the accompanying address, control, power and ground signals required for operation. No current PoP technology can offer 1000 interconnects, due to limited fine-pitch capability within the standard 14mm x 14mm package outline. Although industry expectation is for Through-Silicon-Via (TSV) technology to eventually offer a high-bandwidth solution, TSV manufacturing is still being developed and not expected to be widely available for a number of years. A new high-performance PoP interconnect technology called Bond-Via-Array (BVA [TM]) has been developed to provide high-bandwidth interconnect capability today. A BVA test vehicle package demonstrating 1020 processor to memory interconnects at 0.24mm pitch has been assembled inside the industry-standard 14mm x 14mm package outline. These fine pitch vertical interconnects are achieved utilizing well established wirebond equipment and process. As a result, BVA provides a cost-effective and reliable path to high-performance PoP. This paper details equipment and process developments related to high-volume-manufacturing (HVM) readiness of BVA technology. In addition to assembly process and equipment, test hardware that can accommodate fine pitch wire-tip interconnects needs to be demonstrated for manufacturing readiness. Socket and test hardware development and verification studies utilizing the latest 0.24mm pitch test vehicle are underway in cooperation with a 3rd party test hardware supplier. Goals include demonstrating feasibility of the fine-pitch PoP test approach as well as establishing sources for such hardware. In summary, BVA PoP technology enables 1000+ interconnects in a standard PoP outline while taking advantage of existing materials and infrastructure. To ensure manufacturing readiness, package assembly and test demonstrations are being carried out with third party vendors. Results indicate that with proper design and process optimization, high yield assembly and test is possible, and this technology is ready for high volume manufacturing.