Molded Interconnect Devices Research Articles

Analysis of Tempering Effects on LDS-MID and PCB Substrates for HF Applications

Mechatronic Integrated Devices or Molded Interconnect Devices (MID) are three-dimensional (3D) circuit carriers. They are mainly fabricated by laser direct structuring (LDS) and subsequent electroless copper plating of an injection molded 3D substrate. Such LDS-MID are used in many applications today, especially antennas. However, in high frequency (HF) systems in 5G and radar applications, the demand on 3D circuit carriers and antennas increases. Electroless copper, widely used in MID, has significantly lower electrical conductivity compared to pure copper. Its lower conductivity increases electrical loss, especially at higher frequencies, where signal budget is critical. Heat treatment of electroless copper deposits can improve their conductivity and adhesion to the 3D substrates. This paper investigates the effects induced by tempering processes on the metallization of LDS-MID substrates. As a reference, HF Printed Circuit Boards (PCB) substrates are also considered. Adhesion strength and conductivity measurements, as well as permittivity and loss angle measurements up to 1 GHz, were carried out before and after tempering processes. The main influencing factors on the tempering results were found to be tempering temperature, atmosphere, and time. Process parameters like the heating rate or applied surface finishes had only a minor impact on the results. It was found that tempering LDS-MID substrates can improve the copper adhesion and lower their electrical resistance significantly, especially for plastics with a high melting temperature. Both improvements could improve the reliability of LDS-MID, especially in high frequency applications. Firstly, because increased copper adhesion can prevent delamination and, secondly, because the lowered electrical resistance indicates, in accordance with the available literature, a more ductile copper metallization and thus a lower risk of microcracks.

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.

Flexural Fatigue Test—A Proposed Method to Characterize the Lifetime of Conductor Tracks on Polymeric Substrates

High quality and long product life are two fundamental requirements for all circuit carriers, including molded interconnect devices (MID), to find application in various fields, such as automotive, sensor technology, medical technology, and communication technology. When developing a MID for a certain application, not only the design, but also the choice of material as well as the process parameters need to be carefully considered. A well-established method to evaluate the lifetime of such MID, respective of their conductor tracks, is the thermal shock test, which induces thermomechanical stresses upon cycling. Even though this method has numerous advantages, one major disadvantage is its long testing time, which impedes rapid developments. Addressing this disadvantage, this study focuses on the laser direct structuring of thermoplastic LCP Vectra E840i LDS substrates and the subsequent electroless metallization of the commonly used layer system Cu/Ni/Au to force differences in the conductor tracks’ structure and composition. Performing standardized thermal shock tests alongside with flexural fatigue tests, using a customized setup, allows comparison of both methods. Moreover, corresponding thermomechanical simulations provide a direct correlation. The flexural fatigue tests induce equivalent or even higher mechanical stresses at a much higher cycling rate, thus drastically shorten the testing time.

Laser-Assisted Selective Fabrication of Copper Traces on Polymers by Electroplating.

The selective deposition of metals on dielectric materials is widely used in the electronic industry, making electro-conductive connections between circuit elements. We report a new low-cost laser-assisted method for the selective deposition of copper tracks on polymer surfaces by electroplating. The technique uses a laser for the selective modification of the polymer surface. The electrical conductivity of some polymers could be increased due to laser irradiation. Polyimide samples were treated using nanosecond and picosecond lasers working at a 1064 nm wavelength. An electro-conductive graphene-like layer was formed on the polymer surface after the laser treatment with selected parameters, and the copper layer thickness of 5–20 µm was deposited on the modified surface by electroplating. The selective laser-assisted electroplating technology allows the fabrication of copper tracks on complex shape dielectric materials. The technology could be used in the manufacturing of molded interconnect devices (MID).

Improvement of the Surface Roughness of a 3d Stereolithographic Part for a Molded Interconnect Device

Improvement of the Surface Roughness of a 3d Stereolithographic Part for a Molded Interconnect Device

Alternative manufacturing process of 3-dimensional interconnect device using thermoforming process

In early stages, the electronic circuits have been developed on simple printed circuit boards with multiple copper patterns and components interconnected by lead – free solder. Later on, these are converted to flexible circuits and molded interconnect devices (MID) because of high demand of complex circuit design. Laser machine is used to manufacture 3D MID circuits. An alternative manufacturing process has been introduced in this research. The method is to design functional circuits by using stretchable ink printed on a 2D substrate. Polycarbonate is selected as a substrate on the basis of its glass transition temperature (Tg). Thermoforming process is then applied to transfer 2D substrate into 3D shape. Reverse engineering technique is used to fabricate the mold through several steps. First, the dimensions of rear lighting is calculated by coordinate measuring machine (CMM), transferred to 3D drawing using SolidWorks. And finally the mold is produced using computer numerical control (CNC) machine. Screen printing technique is opted to print ink on a flat thermoplastic Polycarbonate substrate. The highly conductive circuit will be generated after heating printed ink in oven for about 30 min at 120 °C. The circuit with substrate is further transferred into 3D shape using the thermoforming process. All the light emitted diodes (LEDs) are then fixed on a circuit by dispensing conductive adhesive and cured again in an oven for 10 min at 120 °C, so strong bonds are formed at the joints. The reliability of the circuit is assessed by characterizing mechanical and electrical properties. The designed circuit is then compared with the existing design using scanning electron microscopy (SEM), universal testing, two-point probes multi-meter and spectrometer. The electrical performance of new circuit design shows promising results in terms of power consumption and luminous flux of LEDs and there is no major difference found between them. As a result, the new manufacturing process of printed circuit offers encouraging method in manufacturing the automotive lighting product.

Feasibility Study of Soft Tooling Inserts for Injection Molding with Integrated Automated Slides.

The production of injection-molding prototypes, e.g., molded interconnect devices (MID) prototypes, can be costly and time-consuming due to the process-specific inability to replace durable steel tooling with quicker fabricated aluminum tooling. Instead, additively manufactured soft tooling is a solution for the production of small quantities and prototypes, but producing complex parts with, e.g., undercuts, is avoided due to the necessity of additional soft tooling components. The integration of automated soft slides into soft tooling has not yet been investigated and poses a challenge for the design and endurance of the tooling. The presented study covers the design and injection-molding trial of soft tooling with integrated automated slides for the production of a complex MID prototype. The design further addresses issues like the alignment of the mold components and the sealing of the complex parting plane. The soft tooling was additively manufactured via digital light processing from a silica-filled photopolymer, and 10 proper parts were injection-molded from a laser-direct structurable glass fiber-filled PET+PBT material before the first damage on the tooling occurred. Although improvements are suggested to enhance the soft tooling durability, the designed features worked as intended and are generally transferable to other part geometries.

Electrical Activation of Polymer Reny1002H Surface with Laser Irradiation for Molded Interconnect Devices

Electrical Activation of Polymer Reny1002H Surface with Laser Irradiation for Molded Interconnect Devices

Fabrication of Parts with Integrated Circuits by Selective Electroless Plating of Additively Manufactured Plastic Substrates

The use of printed circuit boards (PCBs) has become essential in manufacturing parts with electronic functions. However, the placement of PCBs inside a product requires special plates or fixtures that need to be separately designed, fabricated, and assembled. In addition, PCB manufacturing generally utilizes various toxic metals and etchants. Thus, there is a need to address the issues of space, cost, and environmental toxicity inherent in PCBs. This paper proposes a novel method of fabricating PCB-free part with electronic circuits in a set using the casing or exterior of a product. This process enables the manufacturing of a type of molded interconnect device without conventional molding technologies by directly forming conductive circuits on the side or back of 3D-printed substrates using selective electroless plating. For 3D printing of the product structure, this study uses substrates made of polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS), which are commonly used in the popular material-extrusion 3D printing technology. As ABS and PLA have different chemical properties, the region to be plated with the electrical circuit is fabricated using ABS, whereas the remaining substrate is fabricated using PLA. ABS was chemically treated to allow electroless plating. A process for forming 3D circuits was developed and evaluated by selective electroless plating of the areas of the substrate requiring circuitry. To verify the applicability of the proposed process, circuits and integrated parts used in the industry were redesigned into a single component and fabricated by applying the proposed process. The results demonstrate that the proposed process has good practical applicability. Furthermore, it has low environmental toxicity with low requirements for material consumption and processing energy.

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.

Molded Interconnect Devices in Japan

Molded Interconnect Devices in Japan

Electroless Copper Plating Process Applicable to Molded Interconnect Device Using Laser Direct Structuring

Electroless Copper Plating Process Applicable to Molded Interconnect Device Using Laser Direct Structuring

Manufacturing of Molded Interconnect Device by SKW

Manufacturing of Molded Interconnect Device by SKW

Laser beam activation of polymer surfaces for selective chemical metallization

The application of molded interconnected devices (MID) holds great potential to reduce volume and weight of electronic circuit carriers. The material for laser-based manufacturing usually contents additives inside the matrix, which are required for the activation process. This paper presents an alternative without any additives in the mold. The main focus is the experimental investigation of laser fluence as well as pulse and line distance. The process parameters, that lead to a homogeneous metallization, are described and evaluated in order to define the boundaries of the new laser activation process.

Robust and fast part traceability in a production chain exploiting inherent, individual surface patterns

Abstract Traceability of single parts is essential in automated manufacturing, especially considering recent developments in Industry 4.0 or Smart Manufacturing. In some cases, however, conventional traceability methods, e.g. barcode, DMC or RFID, are not sufficient to track individual components through their entire production chain. One solution is the exploitation of an object’s inherent, individual surface patterns. This work demonstrates label-/tag-free traceability of approx. 1000 components in a molded interconnect device (MID) production chain. The parts’ surface patterns are photographed several times along the MID production chain. Based on the captured images nearly 3300 successful identification processes were performed without any failure. Using a hash algorithm to compress the relevant data of the surface pattern images reduces the required disk space and the runtime significantly. Since the results demonstrate the robustness against surface alterations, this work gives the proof of concept regarding to a method for fast label-/tag-free part tracking that is applicable in an industrial production line.

High-frequency induction heating for increase of flow length in polymer/metal hybrid molding

Recent trends of miniaturization and multi-functionality in electrical parts have driven development of molded interconnect devices (MIDs) that contain conductive tracks on a nonconductive base. This study aims to develop polymer/metal hybrid molding technology to fabricate MIDs in a single manufacturing process, without an additional assembly procedure. For this purpose, injection molding was performed to fabricate a thermoplastic carrier that contained negative circuit channels, and die casting was used to fill the circuit channels with metal alloy of low melting point. To increase the flow length of the molten metal through the narrow circuit channel, high-frequency induction heating was used prior to the die casting stage. The effect of heating conditions on the mold temperature was investigated numerically, and the relevant induction heating conditions were determined accordingly. Induction heating was then applied to the die casting process to increase the flow length enough to be used as a circuit path for fabrication of MIDs.

금속 프린팅 기술을 이용한 성형회로 부품 제조기술 연구

최근 전자제품의 소형화와 다기능화 경향에 힘입어 비전도성 물체 상에 전도성 회로가 형성된 성형회로 부품(MID)에 대한 수요가 증가하고 있다. 본 연구에서는 압출적층형 3D 프린터를 사용하여 금속도선을 출력함으로써 MID 부품을 제조하기 위한 기술을 개발하고자 한다. 특히 열가소성 플라스틱 필라멘트의 출력에 맞춰 개발된 압출부 노즐의 열적 특성을 수치적으로 분석하고, 저융점 금속 필라멘트의 출력이 가능하도록 설계를 변경하였다. 개선된 노즐을 적용하여 금속 필라멘트의 안정적인 출력 조건을 찾기 위한 연구를 수행하였으며, 도선 채널의 형상에 따른 도선부 출력 특성을 고찰하였다. 상기 연구를 토대로 곡선형 도선 채널을 포함한 MID 제품 제작을 위한 연구를 수행하였고, 곡선형 채널에서의 속도 조절에 따라 금속 도선부가 안정적으로 제작됨을 확인하였다.

A Novel Approach for Reliability Investigation of LEDs on Molded Interconnect Devices Based on FE-Analysis Coupled to Injection Molding Simulation

Due to many advantages, such as cost-effective production, design freedom, and weight reduction, plastics have replaced metals and ceramics in many fields. However, engineering plastics are good thermal insulators. This characteristic, although beneficial in certain applications, poses many challenges in many heat-generating applications. This can lead to hot spots or even to an increase in the device temperature. Along with the increasing demand for plastics in areas of the lighting technology or in the automotive field due to the free shaping potential, the requirements are becoming more challenging. Driven by the trend of miniaturization, applications with high heat generation often have to operate in the tightest of spaces. Since not always sufficient space for complex cooling systems is given, the housing or the substrate should assume the task of thermal management. In regard to this fact, the use of thermally conductive thermoplastics seems to be very appealing. Quality loss, poorer reliability, loss of performance, and even failure can occur in case of insufficient heat dissipation. In order to improve the properties of these polymers, highly heat-conducting fillers are added in order to improve the thermal conductivity of the compound. Another technology trend that has been prevalent for years is the use of simulations. Due to shorter product life cycles and therefore shorter development times, simulation has become an indispensable part of the chain of product development. Time-consuming and costly test series make the simulation more and more important as a tool for material and product design. In this context, this paper presents a novel approach for reliability investigation and lifetime estimation, based on simulation. Therefore, a simulative method based on coupling the results from the process simulation (injection molding simulation) to finite element analysis was developed and explained. This coupled method makes it possible to take into account the manufacturing process and its engendered filler orientation. The obtained findings are compared to conventional thermal steady-state analysis and used in order to better predict the lifetime of LEDs mounted on thermoplastic substrates, the so-called molded interconnect devices. It is demonstrated that it is necessary to consider the filler orientation, especially in the case of 3D substrates.

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.

Optimization of Electronic Components Mounting Sequence for 3D MID Assembly Process

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