We report design and test results of a new thermal contact method for PrNi $$_5$$ rod, nuclear coolant compact continuous demagnetization refrigerator (CNDR) which can keep temperature below 1 mK continuously, using Zn soldering rather than Cd soldering. By measuring residual electrical resistance short piece, the resistivity between rod an Ag wires link was estimated as $$1.8\pm 0.1 \times 10^...