well mounted and level with respect to the surface of the printed circuit board while lack of uniformity indicated that the chip was poorly mounted and sloped b clearance the degree of variation in the clearance among the test specimens was evaluated based on the microscopic observations made in a c peeling strength a hole was formed in each printed circuit board beneath the chip the printed circuit board was secured in a jig and the push portion of a tensile test jig was inserted into the hole pressure was exerted by the push portion against the chip until it was peeled off the circuit board the force in kilograms necessary to produced peeling was measured d amount of voids after peeling a chip off a printed circuit board in the manner described in c the surface of the soldered portion was observed to determine the amount of voids e heat cycle life span test specimens were repeatedly subjected to a heating and cooling cycle 55 u00b0 125 u00b0 c the life span equalled the number of cycles before a crack formed in the soldered portion table 1__________________________________________________________________________solder paste compositionexamplenumber composition__________________________________________________________________________present invention 1 63 sn pb powder 325 mesh 90 weight 98 weight solder paste flux 10 weight.