By Gity Samadi and Paul Semenza

Versatile hybrid electronics (FHE) has spawned the event of novel packaging strategies to beat the applying limitations of the inflexible boards, high-temperature solders, cumbersome element packages, and insertion processes utilized in conventional printed circuit boards. Skinny, versatile substrates, naked die, and combos of printed and small-format packaged elements require using additive processes for circuitization, mechanical connect, and encapsulation.

Additive strategies resembling printing with a grasp (e.g., display screen, gravure) or direct write (e.g., ink jet, aerosol jet, extrusion) deposit conductors, insulators, adhesives, and different supplies exactly to connect digital elements to versatile substrates, and the supplies will be cured (e.g., thermal, infrared, ultraviolet, photonic) with out the necessity for prolonged publicity to excessive temperatures.

FHE producers have been working to make use of these novel interconnect and fix strategies in superior packaging to allow extra compact, light-weight, and higher-performance microelectronic methods. Whereas these strategies will not be but generally used, displays at FLEX 2022 in July pointed to intriguing prospects.

Wafer-level printing for packaging

One instance is making use of gravure offset printing to ball-grid array packaging (determine 1). Komori, a supplier of precision printing tools, demonstrated a course of to deposit 30mm pillars of flux paste at 60mm spacing straight on a wafer utilizing gravure offset; 30mm solder balls are then positioned on prime of the pillars in a separate course of.

Fig. 1: Gravure offset printing used to create pillars straight on wafer (l); solder balls positioned on pillars. Supply: Komori

Gravure offset printing has additionally been used to deposit fan-out conductor traces for connecting them to the die pads on flip-chip naked die meeting on versatile substrates (determine 2). NextFlex, the business consortium whose mission is to advance U.S. manufacturing of printed versatile electronics, has demonstrated a course of that mixes gravure offset to print superb (30mm) fan-out traces to the die pad, display screen printing for the hint traces, and gravure offset to put bumps on the die pads.

Fig. 2: Gravure offset printing can be utilized to create superb traces for fan-out (l) and bumps for die pads (r) and mixed with display screen printing to create traces (c). Supply: Komori

Direct-write strategies for energy and RF modules

Whereas FHE is just not usually related to high-power, high-temperature functions, teams engaged on high-performance functions resembling energy and RF modules are exploring combining additive circuit supplies and unpackaged elements on substrates. Along with the potential for compact, low-profile, and conformable packages, additively manufactured modules promise low inductance, important to those high-performance modules.

General Electric, working with Binghamton University, has explored direct-write strategies for setting up silicon carbide energy module packages. The speculation is that such strategies can change wirebonded and planar packages, that are cumbersome and restricted in efficiency (determine 3). Prototypes developed with chosen combos of insulating and conducting supplies and deposition strategies are being evaluated for assembly smaller package deal dimension and decrease inductance necessities.

Fig. 3: So as to overcome the efficiency limitations of wirebonded energy modules (l), planar modules have been developed, which require semiconductor packaging and PCB strategies (c); utilizing direct-write strategies to deposit insulators and conductors (r) presents the potential for conformal/low profile packages. Supply: GE

Binghamton College reported on utilizing an Optomec aerosol jet system for selective deposition and patterning of each dielectric and conductive supplies in a multi-layer construction to create high-resolution 3D circuit parts for millimeter-wave electronics.

Researchers used direct-write patterning at the side of typical low-k substrates and etched copper foil circuitry to allow a less complicated, extra compact package deal. These printed connections confirmed comparable RF and electrical efficiency as wire bonds (determine 4). As well as, the aerosol jet deposition enabled Binghamton to manufacture 3D antenna constructions.

Fig. 4: Metallic-insulator semiconductor (MIS) capacitor related through gold wire bonds (l) and aerosol jet ribbon (r). Supply: Binghamton College

Photonic curing as a substitute for solder reflow

Photonic curing has been used to use conductors, adhesives, and solders to versatile substrates that aren’t in a position to stand up to excessive temperatures. Photonics curing delivers intense bursts of vitality in optical wavelengths to treatment and sinter inks and pastes, in addition to reflow solder – an strategy that has not usually been utilized in conventional (inflexible) electronics, the place high-temperature solder reflow ovens are used.

PulseForge, a supplier of 3D printing and design companies, has developed a digital thermal course of that makes use of a exact, sub-millisecond intense mild pulse from a flashlamp to generate floor temperatures a whole lot of levels greater than these contained in the substrate materials, enabling flowing of solder with out impacting substrate or element supplies. The method allows using commonplace solders with low-temperature substrates, delicate coatings, in addition to different elements resembling batteries and optical gadgets and can be utilized with a wide range of connectors. Whereas the method is just not geared towards inflexible board use, it allows intermetallic thickness to be managed by choosing course of parameters (determine 5).

In comparison with reflow ovens, photonic curing allows processing occasions over 10 occasions quicker in a 3rd of the footprint and consumes solely 15% of the ability.

Fig. 5: Digital Thermal Processing used with a wide range of connection sorts (l). Management of course of parameters allows management of intermetallic thickness on inflexible boards (r). Supply: PulseForge

Convergence of FHE strategies and superior packaging?

Nextflex identified methods FHE can eradicate distinctions between package deal, printed circuit board (PCB) and system (determine 6). For instance, whereas hybrid electronics approaches allow additive printing of circuits and multichip modules, structural electronics allow circuits on and inside components, non-planar surfaces, and 3D constructions.

Fig. 6: FHE in electronics manufacturing. Supply: NextFlex

Hybrid packaging combines additive deposition strategies, chips, and supplies for substrates and boards. NextFlex offered utility examples for these novel packaging approaches, together with wearables and textiles, conformal screens, and lively transport labels. Future element applied sciences utilized in hybrid packaging may probably embrace embedded fluidics, MEMS integration, and photonics and optoelectronics.

Commenting on the potential for integrating 3D printing and additive electronics in packaging, Matthew Dyson of market analysis agency IDTechEx famous that commercialization of partially additive semiconductor packaging utilizing strategies together with laser induced ahead switch (LIFT), laser direct structuring (LDS), aerosol jet, extruded conductive paste, two-shot molding, and print then plate is probably going within the subsequent few years, with totally additive semiconductor packaging a chance inside 5 years. Looking over the subsequent decade, he predicted that totally additive electronics elements might be built-in with surface-mount gadgets (SMD), additive electronics might be utilized in full Heterogeneous Integration.

Integrating FHE with the physique

Bio-inspired applied sciences are key to enabling versatile mechanical methods that may sense and actuate in live performance with the human physique. FLEX 2022 displays by Shane Mitchell of Artimus Robotics, Bryan Starbuck and colleagues from Georgia Tech, and Sheng Xu of UC San Diego pointed to FHE advances which might be enabling skinny, conformal gadgets that may sense a wide range of situations in addition to present actuation.

Artimus Robotics is growing a muscle-like HASEL (hydraulically amplified self-healing electrostatic) actuator expertise that may be designed to increase, contract, or rotate just like the human physique. The expertise makes use of electro-hydraulic actuation, through which electrodes coat each side of a versatile polymer pouch encapsulating a dielectric liquid. By putting a cost throughout the electrodes, the pouch is compressed, enabling managed will increase in strain. The manufacturing makes use of mature and extensively obtainable supplies and processes. The pouch will be made with cheap supplies resembling polypropylene (PP), polyethylene terephthalate (PET), thermoplastic polyurethane (TPU), or polyvinylidene fluoride (PVDF), and the dielectric fluid can likewise use frequent supplies resembling vegetable or silicone oil.

Manufacturing HASEL gadgets includes utilizing warmth to seal and form movies, display screen printing or different bulk deposition for the electrodes and filling the pouches with dielectric fluid and dip coating to encapsulate the system. Artimus Robotics has additionally designed a high-voltage energy provide that independently addresses 10 channels as much as 10 kV every, powered by two 3.7 V, 2500 mAh lithium polymer batteries; the ability provide weighs 250g and measures 8.4cm × 13.3cm × 2cm. An built-in microcontroller allows a suggestions loop that enables capacitive sensing throughout the electrodes to gauge the spacing of the electrodes and the diploma of motion.

Fig. 7: Human-machine interfaces (prime) and industrial automation (backside) are among the many functions Artimus Robotics envisions. Supply: Artimus Robotics

Specializing in functions and applied sciences that assist help motion in folks with neuromotor problems and growing old muscle, Georgia Tech is growing a versatile system that makes use of sensory suggestions via electromyography (EMG) to evaluate muscle and motor neuron well being and augments power via pneumatically actuated synthetic muscle. The electromyography system makes use of nanomembrane electrodes, fabricated via E-beam evaporation that conform to the pores and skin and measure voltage variations in muscle tissue.

The George Tech group developed a versatile circuit board with A/D converter and Bluetooth low-energy transceiver chips. The versatile board is encapsulated on prime of the electrodes and includes a rechargeable battery. The group is changing the EMG knowledge to photographs used to coach a convolutional neural community and predict motions utilizing deep studying. The predictions can then be used to direct a pneumatic system to reinforce human muscle.

Present wearable gadgets utilizing comfortable electronics can detect very important indicators on or close to the pores and skin utilizing electrical indicators resembling electrocardiogram (ECG or EKG), oxygen degree (pulse oximetry), temperature, some movement knowledge, and chemical knowledge through sweat. Sheng Xu’s group at UCSD has embedded electrodes and ultrasonic transducers in silicone to manufacture comfortable ultrasonic transducer arrays that conform to the pores and skin and may fold, stretch, and twist. As well as, the group developed wearable phased arrays that may penetrate deep into tissue at excessive decision and with lively steering, in addition to apply Doppler imaging to cardiac tissue.

Paul Semenza is advisor to SEMI on particular tasks. He was beforehand with NextFlex, the Versatile Hybrid Electronics Manufacturing Innovation Institute.

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