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Solder balling test
This test is part of standard conditions established for solder paste at Phillips. It is used for evaluating the reflow suitability of a solder paste on a non-wettable substrate. (thickness 0.6-0.8 mm, length 50 mm, width 25 mm), A 0.1 ± 0.001 mm thick adhesive film with an opening of 5.5 ± 0.1 mm ∅ is glued onto a non-wettable aluminum oxide plate and the opening is smeared with a small amount of solder paste. The adhesive film is then removed with a spatula, so that a layer of solder paste of about 0.07 mm thickness and with a diameter of 5.5 ± 0.1 mm will be left behind. The distance between such individual holes should be at least 10 mm. The plate is then heated over a Sn60-Pb40 solder bath (250 °C ± 2 °C), with the coated side facing up. The result should be evaluated according to the following table. The test is performed on samples that have been stored under normal atmospheric conditions after the application of solder paste for 0, 24 and 72 hours, respectively. This test is describet in IPC TM650 as well.