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APRIL 2022 I PCB007 MAGAZINE 85 e ASEP process starts with a stamped metal carrier which is over-molded with a high temperature substrate. A nanoparticle ink is used to print the patterns and then the traces are electroplated with conventional metals commonly used in the PCB industry (Figure 2). A solder mask is applied and then compo- nents are reflowed onto the ASEP assembly. e stamped metal carrier within the ASEP assembly serves multiple crucial functions in the manufacture of the product. e substrate is a way to carry the ASEP assembly through the manufacturing process steps as well as the electrical contact for the connector features of the ASEP assembly. In addition, the substrate serves as a method to transfer the heat gener- ated by the components placed onto the ASEP assembly and provides a path to carry high current that would otherwise be impossible to carry within a conventional PCB assembly. For higher density electronic packages, a two-sided reel-to-reel manufactured poly- imide flexible circuit either replaces or is inte- grated with the stamped metal carrier, creat- ing up to five layers of circuitry. is type of ASEP packaging would be used to design miniaturized con- sumer electronics, sensors, medical devices, and small wearable devices. For high temperature applications, a thermally conductive substrate such as a liquid crystal polymer (LCP) is used; it effectively becomes a heat sink or spreader, reducing the tem- peratures of the heat-generating components. Aer the stamped metal carrier has been over-molded with an LCP substrate, a laser is used to define the circuit patterns on the surfaces of the substrate. Since all the 3D fea- tures such as vias, recesses, or cav- ities have been molded into the substrate, the laser must be able to image the pattern in three dimen- sions. Aer the patterns have been laser marked, an inkjet printer deposits a thin conductive layer of metal onto the traces that were defined by the laser. ASEP Attributes, Features, and Performance By integrating the functionality of a PCB, connector, and thermal management features, ASEP combines the functions into a single device which will be smaller, lighter, and more efficient. Because the process is fully additive, new SAP processes will be able to provide fine traces and spaces. Advantages are that ASEP applications can be made to be inherently her- metically sealed. e combination of these advantages should result in very cost-effective electronic solutions. Figure 3 shows an ASEP package with- out components. e package, called ASEP microPDB (micro power distribution box), adds additional power switching and circuit protection to the vehicle's wiring architecture. e two high-current electrical paths for the field effect transistor (FET) in the lower bot- Figure 3: An ASEP microPDB substrate without components. The FET will be soldered to two of the contacts on the microPDB that are direct extensions of the 800-micron thick copper alloy contacts.