A heat-exchanger in a chip tester includes an electric heater and a heatsink which are joined together with a layer of an attach material. The operational period of this heat-exchanger is extended by a method which includes the steps of: 1) testing chips in the chip tester in a manner that puts the heat-exchanger through multiple temperature changes which keep the layer in a solid state and which induce stress-cracks in the layer; 2) subjecting the layer to a crack-healing temperature cycle in which the layer is melted at least partially and re-solidified; and thereafter, 3) repeating the testing step.