Abstract
The Low Temperature Joining Technique (LTJT) using silver compounds
enables to significantly increase the thermal conductivity between joined
elements, which is much higher than for soldered joints. However, it also
makes difficult to measure the thermal conductivity of the joint. The
Laser Flash Analysis (LFA) is a non-intrusive method of measuring the
temperature rise of one surface of a specimen after excitation with a
laser pulse of its other surface. The main limitation of the LFA method is
its standard computer software, which assumes the dimensions of a bonded
component to be similar to those of the substrate, because it uses the
standard Parker’s formula dedicated for one-dimensional heat flow. In the
paper a special design of measured specimen was proposed, consisting of
two copper plates of different size joined with the sintered silver layer.
It was shown that heat properties of these specimens can also be measured
after modifying the LFA method. The authors adapted these specimens by
masking the false heat signal sourced from the uncovered plate area.
Another adaptation was introducing a correcting factor of the heat travel
distance, which was calculated with heat-flow simulations and placed into
the Parker’s formula. The heat-flow simulated data were compared with the
real LFA measurement results, which enabled estimation of the joint
properties, e.g. its porosity.
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