Patent ID: 6138893
Filing Date: 2000-10-31
Classification: B23K,H05K

Abstract:
An arrangement for measuring the cooling rate and thermal gradient between an upper surface and a bottom surface of a printed circuit board during a time interval in which critically located solder joints of a module located on the upper surface of said printed circuit board are solidifying in a cooling section of a reflow solder oven; comprising:(a) a plurality of through-holes extending through said printed circuit board from the bottom surface to the top surface at least at spaced locations over the surface of on said printed circuit board;(b) a thermocouple wire extending through each said through-holes;(c) a first thermocouple being positioned on said upper surface proximate each said through-hole and connecting said thermocouple wire to said first thermocouple;(d) a second thermocouple being positioned on said bottom surface and connecting said thermocouple to said thermocouple wire; and(e) upper and lower pairs of said thermocouples being operative connected for measuring the temperature differential between said upper and bottom surfaces through the temperatures sensed by said first and second thermocouples at each respective said locations on said printed circuit board, each said first and second thermocouple pairs being located in specified identical upper and bottom surface locations on said printed circuit board and selective multiple locations to facilitate ascertaining and correcting of potentially damaging thermal gradients encountered between said upper and bottom surface; wherein said pairs of upper and lower thermocouples sense temperature differentials at a plurality of said critically located solder joints selectively defining diagonal points of the module, middle of the module, leading edge of the board at three points, trailing edge of board at three points, and the centerline of the board at three points between leading and trailing edge.