Molded Interconnect Device Technology Research Articles

Radial Line Planar Phased Array Using Electromechanically Rotated Helical Antennas

In this paper, we propose a novel radial line planar phased array in which helical antenna elements are individually rotated by their respective connected micromotors to realize dynamic beam-scanning. To our knowledge, this is the first radial line planar array (RLPA) that has antenna elements electromechanically rotated by their individual micromotors. To facilitate its fabrication, helix and its probe are directly metallized on a plastic shaft using molded interconnect device technology, and a motor shaft is press-fitted into the plastic shaft. We also present a new design methodology for RLPA, which combines the equivalent circuit theory and electromagnetic simulations of the unit cell element. The proposed procedure is practical to design an RLPA of antenna elements with arbitrary probe shape without large-scale full-wave analysis of the whole structure of the RLPA. We design, fabricate, and evaluate a 7-circle array with 168 helical antenna elements fabricated using molded interconnect device technology. The prototype antenna exhibits dynamic and accurate beam-scanning performance. Furthermore, the prototype antenna exhibits a low reflection coefficient (less than -17dB) and high antenna efficiency (above 77%), which validates the proposed design methodology.

3D Plastronics for Smartly Integrated Magnetic Resonance Imaging Coils

Over the last four decades, magnetic resonance imaging has become the gold standard imaging technique in many medical diagnoses for brain, cardiac, and liver disease. However, due to low critical mass and great scientific challenges, instrumentation dedicated to preclinical MRI imaging has lagged behind instrumentation for clinical applications. The aim of this paper is to demonstrate that a set of new technologies such as the 3D Molded Interconnect Devices technology preferably named below as 3D Plastronics, 3D Printing, and Microfluidics may be considered to provide a completely new way for designing preclinical MRI setups, i.e., the 3D prototyping and manufacturing of the MR coil, the sample holder, and the peripherals, all together. The fabricated MRI setup can be used both for MRI of small biological samples and for in vivo imaging of a mouse brain. This work is the first step toward the full 3D manufacturing of tailor-mad multifunctional MRI probes.

Development and Validation of a Novel Setup for LEDs Lifetime Estimation on Molded Interconnect Devices

Higher energy efficiency, more compact design, and longer lifetime of light-emitting diodes (LEDs) have resulted in increasing their market share in the lighting industry, especially in the industries of consumer electronics, automotive, and general lighting. Due to their robustness and reliability, LEDs have replaced conventional light sources, such as fluorescent lamps. Many studies are examining the reliability of LEDs as such or investigating their long-term behavior on standard printed circuit boards (PCB). However, the thermal performance of LEDs mounted on nonconventional substrates is still not explored enough. An interesting example for this is the molded interconnect devices (MID), which are well known for the great design freedom and the great potential for functional integration. These characteristics not only underline the main abilities of the MID technology, but also present some challenges concerning thermal management. The long-term behavior of LEDs on MID is still quite untapped and this prevents this technology from consolidating its existence. In this context, this work highlights a developed test setup aimed at investigating LEDs, mounted on molded interconnect devices, under combined stress conditions. The results of the reliability study, as well as the resulting lifetime model, are also illustrated and discussed.

On the quality and the accuracy of the laser direct structuring, experimental investigation and optimization

The enormous applications of the molded interconnect devices (MID) make these face many difficult challenges, some of which are the quality and the reliability, as well as concerns on how to produce the micro-MID products. This drives to a hard competition between the different methods used in the MID technology. The laser direct structuring (LDS) has clearly been distinguished as the best method in comparison with the other MID processes. However, it also needs more development, especially in terms of the quality, accuracy, and their impact on the final MID quality of the two- (2D) and three-dimensional (3D) micro and normal products, especially with the decline or the limited availability of information in both of the industry and scientific research. In this work, the MID-LDS has been experimentally investigated by considering the effect of the important process parameters on the process responses and then to explore the relationship between these responses and the final MID quality and reliability. These experimental works were based on the design of the experimental tool, which employed a full factorial design for the LDS process parameters. They include the laser power, structuring speed, laser frequency, hatching percentage, the incident angle, and the focal length. The experiments have been performed on the polymer plates of Poly Ether Ether Ketone (PEEK) materials. During the experiments, different measurements have been implemented to find out the correlation between the adopted parameters and the 3D surface roughness, structuring percentage, structuring type, and ablation type, which are regarded as the most important features of LDS quality. Further measurements focus on the LDS accuracy and the final quality and reliability of the metallization structure, which includes the metallization thickness, the surface roughness, and the adhesion strength. The analysis of these experimental results showed that the quality and reliability, especially the adhesion strength and the surface roughness, of the final MID products are deeply related to the structuring percentage, structuring type, ablation type, and finally, the surface roughness.

Reliability Study and Thermal Performance of LEDs on Molded Interconnect Devices (MID) and PCB

Light-emitting diodes (LEDs) have increasingly replaced conventional lamps in the fields of general lighting and consumer electronics. In addition to the sharp price fall, this is also due to the significantly higher energy efficiency and the smaller, more compact design. Recently, their robustness and reliability have also reached a level of quality that surpasses the characteristics of conventional light sources such as halogen and fluorescent lamps. Characteristics, such as excellent design freedom and the possibility for functional integration, highlight the main qualities of molded interconnect devices (MIDs). The use of this technology does not only open doors to extend the application field of LEDs to new products but also presents challenges to the lighting industry. There are many studies dealing with the reliability of LEDs as well as with the usability of the MID technology in different fields. But, the lack of experience from the manufacturers regarding the behavior of this interesting configuration (LED/MID) over the entire life cycle prevents this technology from establishing and consolidating its existence. As LEDs in the automotive sector, especially within headlamps, assume increasingly powerful lighting tasks and are no longer used exclusively for signal transfer or for displays, thermal properties of the substrate materials and the thermo-mechanical behavior of the assembly are particularly relevant. In this context, this paper presents a deep and detailed reliability investigation of this system (LED/MID) and examines the influence of the MID substrate choice on the long-term performance of the LED. The impact of the forward current and of the ambient temperature on the junction temperature of the LED is a proven fact. Therefore, the MID effect was inspected under different operating conditions based on infrared thermography. After analyzing the occurred failure mechanisms, by means of X-ray analysis, thermal transient testing and microscopy, the resulting lifetime model is also presented and discussed.

Investigations on Flexural Fatigue Strength of Conductor Paths Fabricated by LPKF-LDS® Technology

Reliability aspects are crucial for the success of every technology in industrial application. Regarding interconnect devices, several methods are applied to evaluate reliability of conductor paths like accelerated environmental tests. Especially, molded interconnect devices (MID), which enable numerous applications with three-dimensional (3D) circuitry on 3D shaped injection-molded thermoplastic parts are often under particular stress, e.g., as component of a housing. In this study, a new test method for evaluating the flexural fatigue strength of conductor paths produced by the laser-based LPKF-LDS® technology is presented. For characterization of test samples, a test bench for flexural fatigue test was built up. A result of the flexural fatigue test is a characteristic Woehler curve of the metal layer system. Applying this new test method, essential influencing parameters on the reliability of MID under mechanical load can be identified. So, the metal layer system as well as the geometric parameters of the metal layer is crucial for the performance. Furthermore, test specimens are tested under different types of mechanical load, i.e., tensile stress and compressive stress. For a holistic view on reliability of MID, experimental results are discussed and supported by simulations. An important finding of the study is the advantage of nickel-free layer systems in contrast to the Cu/Ni/Au layer system, which is often used in MID technology.

Void Formation and Their Effect on Reliability of Lead-Free Solder Joints on MID and PCB Substrates

Since the introduction of lead-free solder alloys, the impact of voids in solder joints has rapidly gained in importance. Particularly in power electronics, voids in solder joints can reduce their reliability due to less heat dissipation and a significant reduction of the cross-sectional area. While void formation in the printed circuit board (PCB) technology has been the focus of many research projects, the increasing application of molded interconnect devices (MIDs) demands a vivid understanding of void formation and its impact on reliability. This report will show that those processes specific to MID technology do not significantly influence the void formation in SAC305 solder deposits. The processed different roughness levels on Vectra, Vestamid, and FR4 substrate materials show no significant impact on void formation. The surface finish metallization was detected as the most important factor. Especially, the chemical-Sn (iSn) surface finish is inclined to having more voids compared to a nickel–phosphor–gold (NiP-Au) finish. Furthermore, three solder processes were investigated: convection, condensation, and vacuum-condensation soldering. The vacuum-condensation processes significantly reduced the voids in the Sn–3.0Ag–0.5Cu (simplified as SAC305) solder joints of CR0805, MLF20, and switches on all the investigated substrates. An accelerated thermal cycling test of these components according to JESD22-A104D demonstrates no significant effect of the void content of <19% on the solder joints’ reliability. Finally, the result of accelerated thermal cycling shows the possibility to achieve an equivalent lifetime of the solder joints on Vectra in comparison to the FR4 substrate.

Function-based Feasibility Study and Benchmark for MID Concepts

Molded Interconnect Devices (MID) are three-dimensional structures with integrated electronic circuit traces that facilitate the miniaturization and functional integration of technical products. This opens up new possibilities for the conception and design of products but also comes with specific challenges. The complexity of MIDs has a major influence on the design process of the product and the design of the associated manufacturing system. There are a large number of available MID manufacturing processes composed of various steps, each one with specific advantages and constraints attached to them. As a result, the manufacturing process has to be taken into consideration at an early stage of the product development cycle. A systematic design approach is therefore necessary in order to successfully create a feasible product using MID technology. This paper presents the first part of a procedure that enables a systematic conception of MIDs and the associated manufacturing system while taking product functions into account, starting with a feasibility study for MID concepts.

Application of Molded Interconnect Device technology to the realization of a self-biased circulator

This paper describes the first electromagnetic characterization of a self-biased circulator in molded interconnect device (MID) technology. The circulator was designed using a 3D full-wave commercial simulator. It consists of microstrip access lines connected to a Y-junction in Substrate Integrated Waveguide (SIW) technology. Unlike classical technologies, the SIW Y-junction was not fabricated using metallic vias but by a Laser Direct Structuring (LDS) technique. A molded Cyclo-Olefin Polymer (COP) was used as a substrate and 3D metallized. The microwave properties of LDS-compatible COP are not well known so we investigated them through the use of cavity-perturbation and rectangular waveguide characterization methods. The device was then machined to insert a pre-oriented strontium hexaferrite puck doped with cobalt and lanthanum (Sr0,7La0,3Fe11,7Co0,3O19). The characteristics of the MID circulator were assessed between 28 and 32GHz. Without magnets, insertion losses of 3.32dB were measured at 30.7GHz. At the same frequency, an isolation level of 13.89dB and return losses of 19.89dB were observed. These measurements demonstrate for the first time the high potential of MID technology for the realization of low-cost non-reciprocal devices.

CPW-Fed Inkjet Printed UWB Antenna on ABS-PC for Integration in Molded Interconnect Devices Technology

This letter highlights the potential of inkjet-printing on molded interconnect device technology for the realization of ultrawide band (UWB) antennas. Low-cost thermoplastic acrylonitrile butadiene styrene polycarbonate (ABS-PC) substrate is selected for its promising mechanical and thermal properties. First, electrical characterizations of bare ABS-PC are done using resonance cavity method and then the measurements of S-parameters of two 50 Ω-CPW transmission lines, allow the extraction of both relative permittivity and RF losses. Inkjet printing of silver nano ink is used to fabricate those CPW lines on the top of a 2-mm-thick ABS-PC. The measurements show a relative substrate permittivity equal to 2.8 with conductive and dielectric losses of 19.5 dB/m and 2.4 dB/m at 2 GHz, respectively. Then, an UWB antenna based on a half circular disc monopole and a rectangular patch with two steps is designed and realized by inkjet on ABS-PC. This printed antenna provides a good impedance matching over the entire bandwidth of 3 GHz-13 GHz. Radiation pattern is omnidirectionnal in both E and H planes until 5 GHz and is deformed at higher frequencies due to the higher order modes.

Design and Solder Process Optimization in MID Technology for High Power Applications

Molded interconnect device (MID) technology is a key enabling technology with growing markets in automotive, communications, consumer electronics through integration with lighting and sensor technologies. The MID technology is yet to be explored for high temperature applications in automotive or consumer lighting. One of the hindering factors for such implementation in the serial production and time to market is the improper electronic and thermal packaging of the light emitting diodes (LEDs) on the MID substrates. This paper addresses the optimization of mold design, surface metallization and soldering process for the effective thermal management of the high-power LED systems. By using a simulation model, the thermal distribution and the resultant decrease in temperatures for varying forward electrical currents in high-power LEDs by design optimization is demonstrated. In addition, the optimization of solder process with respect to solder profile in context of vacuum vapor-phase soldering for void-free solder connections is discussed.

Comparison of methods for broadband electromagnetic characterization of Molded Interconnect Device materials

Abstract. Combining the Molded Interconnect Device technology with the Laser Direct Structuring technology exhibits the potential of designing electrical and mechanical components on three-dimensional surfaces to increase functionality, level of integration and to reduce costs. When taking advantage of this technology especially in the design of RF devices, a precise knowledge of the electromagnetic parameters of the MID material is required, as the complex permeability and permittivity strongly influence the device performance. At present time, these materials are not electromagnetically characterized in the RF frequency range. In this paper different methods are therefore presented and compared with respect to their potentials for broadband electromagnetic characterization of Molded Interconnect Device materials.

Duromer MID technology for system-in-package generation

The Duromer molded interconnect device (MID) technology for realization of a stackable system-in-package (SiP) is similar to conventional MID technology, which is usually realized using thermoplastic polymers, combining the functionality of housing and substrate into one device. Advantages of the conventional MID technology are the reduction of parts during assembly by integrating mechanical and electrical functionality into a device and the reduction of space, as MID allows a three-dimensional (3-D) integration of devices. A disadvantage of conventional technology, especially if combined with typical technical thermoplastics, is the large mismatch in coefficient of thermal expansion (CTE) between substrate and advanced microelectronic components as chip scale package (CSP) or flip-chip. This is reducing the applicability of thermoplastic MID to moderate temperature ranges and/or to rather robust components. To overcome this disadvantage, the use of low CTE duromer as epoxy molding compounds (EMCs) as base material for device assembly is proposed, generating a unique technology well adapted to SiP and microelectromechanical system (MEMS) packaging needs, the Duromer MID approach. The technological realization of Duromer MID uses conventional backend processes as IC bonding to flex, transfer molding using epoxy molding compounds, laser machining, metallization, and structurization processes well known from PCB processing. The use of existing equipment allows both a rather fast process implementation and a cost-effective manufacturing of the components. Within this paper, the investigations described previously are driven further toward a description of a generic packaging technology integrating detailed analysis of metallization processes and assembly issues. Summarized, this paper presents further process development and feasibility analysis of wafer-level packaging technologies for SiP solutions based on a Duromer MID approach.

Alternative Placement Systems for Three-Dimensional Circuit Boards

The three dimensional circuit board technology leads to advantages and new special challenges concerning electronics assembly. Two different placement systems were realized at the FAPS institute. The first concept was developed to extend the limits of a Cartesian Placement System. An advanced module for handling the Molded-Interconnect-Device-Technology (MID) in the working space of a SMD assembling system, as well as the use of a pipette with an additional axis, make the 3-dimensional assembly of components into MID possible. The second concept is a Robot Placement System, which consists of hardware components like a six axis robot, a tool changing system, a transport system, moving feeders and a vision system. A critical point in surface mounted technology is the necessary accuracy in centering the SMD to the pipette and the accurate placement of components. This is realized with the use of vision systems. Thereby, a new strategy for failure compensation was developed. A way to optimize the control structures and kinematic of MID placement systems is the use of modern simulation-based development and test systems, which provide facilities to perform structural analysis, collision detection, cycle time calculation as well as off-line programming capabilities.