Fig. 4
From: Applying microscopic analytic techniques for failure analysis in electronic assemblies
Pores and cavities in through-hole solder joint. The measured vertical fill with solder paste for the left solder joint is 499.8 μm, the height of the THT hole is 1557.2 μm. So the vertical fill with solder paste is calculated by (499.8/1557.2) × 100% = 32.1%. The void in the left solder joint is about 67,9% of the vertical height of the solder joint, in the right solder joint the void is about 53,3%. The vertical fill with solder paste is < 75% as specified in the standard, so that this solder joints are not accepted (a). Also in the horizontal cross-section voids can be found in the solder joint. In this case the solder joint is well formed, the void does not influence the mechanical stability of the solder connection (b) (Figure captured using Olympus BX61 metallographic microscope at a magnification factor of 50x)