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A novel self-packaging technique of electrical-optical circuit boards (EOCB) has been developed based on a combination of a patented PDMS waveguide fabrication technique and a process for efficient interfacial bonding between PDMS optical layers and standard FR4 printed circuit boards (PCB) materials (Glass Reinforced Epoxy). The main mechanism of forming a good bonding between PDMS and FR4 has been identified. It is based on a strong chemical intermolecular reaction between the PDMS prepolymer and the FR4 substrate caused by a special surface-adhesion-promoter (SAP) added to the PDMS prepolymer and an O2 plasma treatment of the FR4-substrates. The optical and mechanical properties of the PDMS waveguide layer remained unchanged by the addition of the SAP. Presently there are no standard test procedures for EOCBs yet, and thus environmental test procedures to check the optical and mechanical stability performances of EOCB were developed and applied to PDMS-waveguide layer based EOCBs. According to the defined procedures, the environmental stability of packaged EOCBs has been tested with the result that they exhibited excellent mechanical, optical, and thermal stabilities. The mechanical stability limit of the tested EOCBs is determined only by the intrinsic mechanical stability of the used PDMS materials. The optical waveguide propagation loss at 850 nm is less than 0.1 dB/cm after surviving from the defined environmental test procedures.