Increased Functionality for IoT through Flip Chip Die Attach of Wire-Bondable Chips on Flexible Hybrid Electronics (FHE)

Using Magnetically Aligned ZTACH® ACE
Smart label product tags (e.g. RFID tags) are ubiquitous for inventory control and asset security but require ever more functionality to support the Internet of Things (IoT). There are many options on the market for functional die with advanced capabilities beyond ID logging, such as environmental or positional recording. However, these chips are often designed for wire bonding interconnection; preventing them from being readily used in Flexible Hybrid Electronics (FHE) applications. SunRay Scientific will present success of flip chip attachment of a commercially available NFC bare die designed for wire bonding using a standard SMT line. The die were attached using a novel anisotropic conductive epoxy, ZTACH® ACE, for flexible hybrid electronics (FHE). Implementation of a successful interconnection with flip-chip bonding is nontrivial, but there are significant advantages to be found with success. Attaching a die using a flip-chip bonding requires fewer process steps than wire bonding. The size of the circuit is significantly reduced through the elimination of the wire bond pads around the periphery of the die. Flip chip bonding is also more amenable to the materials used in FHE than wire bonding. These advantages combined with the low temperature and high-speed processing of ZTACH set the stage for mass produced inexpensive connected FHE sensors. The ZTACH® ACE material is composed of a binary epoxy resin loaded with ferromagnetic particles that have a high electrical conductivity coating. During the curing of the epoxy, a magnetic field is applied
using SunRay’s patented ZMAG® Magnetic Pallet, causing the ferromagnetic particles to align in columns forming a low electrical resistivity path through the thickness of the epoxy (and between the components and matching bonding pads), while maintaining very high electrical isolation laterally between pads. The epoxy upon cure also serves as an underfill eliminating the need for an additional process step. ZTACH® ACE material and processing reshapes current FHE packaging via single-step packaging of mixed electronic components that otherwise cannot handle elevated pressure and high temperature during assembly. Additionally, lower profile component attachment is enabled on flexible substrates so smart labels are not limited by rigidity and thickness, allowing addition of security features and integrated sensing, while decreasing costs and meeting performance requirements. This emerging anisotropic conductive epoxy is compatible with SMT lines’ sheet-to-sheet (S2S) processing. The goal of this talk will be to demonstrate the possibilities of transitioning existing wire-bondable functional bare die to FHE systems using ZTACH® ACE and existing SMT infrastructure. With additional process development, this approach of enabling manufacture of enhanced capability IoT systems using existing die and SMT infrastructure could be made widely available to US contract manufacturers.