The report of through-hole formation using
the conductive paste

Procedure of double-side through-hole formation
1.	The drilling process First, make holes by drilling, then be sure to remove the burrs.
2.	Paste coating process Viscosity control. Attenuate paste by thinner into dilution rate 5 %. Fill the paste all over the substrate board by squeegee. In order to prevent the paste from remaining on the substrate board aside from the through-hole, you have to remove the paste by squeegee thoroughly.
3.	Preliminary drying Perform 90 minutes in 60 degrees C. In case that preliminary drying is not sufficient, it emerges void inside of the through-hole, leading to cause the poor conductivity.
4.	Hardening process Perform 30 minutes in 150 degrees C. Remove the oxide film from the copper foil surface after hardening. Removal of the oxide film should be done by the acid treatment instead of the physical ablation. (In this experiment, we used the detergent for the bathroom.)
5.	Processing circuit pattern Process the circuit. It requires the accurate position adjustment. Cross-section surface of the through-hole