Advanced Materials Research Vol. 1038

Abstract: A novel laser induced metallization (LIM) is developed for 3 dimensional molded interconnect devices (3D-MIDs). A special laser-activable solution is firstly sprayed on top of the substrate, followed by laser direct structuring (LDS) and the electroless plating. The metal patterns can be transferred from the CAD data on almost any complex surface. Compared to the direct LDS, our spray method has smaller linewidth (30 μm) and much more flexibility on the substrate choosing. For example, the substrate can be plastic, glass, or ceramic. In addition, the laser-activable solution on top of the substrate also plays a role of the insulator. As a result, the multilayer patterns can be made by simply repeating the spray method on the same surface. Moreover, since this method is capable of making patterns layer-by-layer, the capacitors and inductances can be direct integrated with the circuit design. In this report, a 2G/3G/4G (all-in-one) antenna is tested by using our spray method. The return loss reaches the 3:1 VSWR standard, and the radiation efficiency is larger than 60% within the operation frequency.

Abstract: Embedding stereolithography (eSLA) is an additive, hybrid process, which provides a flexible production of 3D components and the ability to integrate electrical and optical conductive structures and functional components within parts. However, the embedding of conductive circuits in stereolithography (SLA) parts assumes usage of process technologies, which enables their direct integration of conductive circuits during the layer-wise building process. In this context, a promising method for in-situ generation of conductive circuits is dispensing of conductive adhesive on the current surface of the SLA part and its subsequent sintering. In this paper, the laser sintering (λ = 355 nm) of conductive adhesive mainly consisting of silver nanoparticles is investigated. The work intends to evaluate the curing behavior of the conductive adhesive, the beam-matter-interactions and the thermal damage of the SLA substrate. The investigations revealed a fast and flexible laser sintering process for the generation of conductive circuits with sufficient electrical conductivity and sufficient current capacity load. In this context, a characterization of the conductive structures is done by measuring their electrical resistance and their potential current capacity load.

Abstract: Electronic circuit boards have been fabricated in cycle times of a few seconds by ultrasonic fabrication. A stack of thermoplastic polymer foils with a copper layer, 20 μm in thickness, on top is transformed into a polymer carrier with separated conductor paths. This process is accomplished in cycle times of a few seconds and the required equipment is just a commercially available ultrasonic welding machine and a metal tool micro patterned, e.g., by milling.Since soldering is often not possible on a thermoplastic carrier, electronic components are joined to the conductor paths by ultrasonic welding. This is achieved by employing an anisotropic conductive foil containing metal particles providing the electrical contact normal to the foil and showing no conductivity in lateral direction. The anisotropic conductive foil also serves as glue between circuit board and electronic components.

Abstract: Due to their vast number of benefits, plenty of complex and miniaturized three dimensional molded interconnect devices are developed. One especially demanding process step during their manufacturing is the geometrical exact creation of the conductive pattern layout on the different substrates’ faces. Therefore, sophisticated and flexible technologies like laser direct structuring or printing processes can be used, which are subject to multiple research activities, concentrating for example on coating materials or process parameters. An additional aspect is the necessity of providing a flexible and sufficiently accurate handling device, which three dimensionally moves the substrate relative to the process nozzle applying the coating material. For this task industrial robots could be used, which inherit multiple beneficial features. One main drawback of using this type of kinematic is their relative low absolute accuracy of a few hundred microns, which is not sufficient for moving the substrate during the process with the needed accuracy.

Abstract: The production of Molded Interconnect Devices (MIDs) may be achieved through different processes. In this work Centro Ricerche Plast-optica (CRP) has chosen to evaluate, implement and assess Laser Direct Structuring (LDS) and In Mold Labeling (IML) technologies for the production of MIDs. Both alternative methods have been analyzed starting with a 2D component, mainly used for implementation and optimization of the process, and finally a more complex 3D component, that has been designed and produced. The first phase of the activity regards the production of several conductor patterns on planar substrates dedicated to evaluate properties as conductors resistance, adhesion, SMD components solderability, wire bondability of bare LED dice etc. In the case of IML, a flexible circuit has been over-molded during the production of the component by injection molding process: planar parts have been tested also in terms of adhesion of flexible circuit to the injected polymer. The second phase of the activity concerns the production of 3D circuits. Both technologies have been implemented in order to select to materials, process conditions and parameters, design rules and to verify the reliability in the automotive severe conditions. Exploitation of technologies have been performed on an automotive rear lamp. A prototype has been produced in LDS technology and allowed to define the conditions that make economically affordable this solution. Differently, the IML technology allowed to produce a completely new device by embedding a planar electronic circuits into the plastic material.

Abstract: 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.

Abstract: The adhesion test of metallic structures on MID (Molded Interconnect Devices) parts is an unsolved issue. So far no method really works reliably. The test methods which are conventionally used are the pull-off test and the shear-test. Both show large standard deviation and the reproducibility is not assured. Nordson DAGE has introduced the new micro-material testing system 4000Plus. This device enables a new test method for the determination of the adhesion strength of MID structures using the hot pin pull (hot bump pull) method. Copper pins (tinned or untinned) are heated up with a user defined temperature profile, soldered to a metallized structure on the MID and then removed vertically upward, while the force is recorded. In this contribution investigations with this new test method are presented.