Magnetic Selection of Parts According to Local Plating Thickness
Original Publication Date: 1985-Nov-01
Included in the Prior Art Database: 2005-Feb-19
In the multilayer ceramic (MLC) soldering process, some parts, e.g., MLC pins, are required to have a non magnetic coating of specified thickness (in certain areas) over a ferromagnetic base material to allow incoming parts to be tested and culled according tot he local plating thickness. A magnetic selection of parts measures the local thickness of nonmagnetic coatings over ferromagnetic substrates both nondestructively and inexpensively, and efficiently culls the parts according to the local plating thickness. An electromagnetic head 11 (Fig. 1) exerts a force between head 11 and the ferromagnetic material 12. Such a force is sensitive function of the distance, z, between the two. This distance is determined by the local thickness of the nonmagnetic coating 13, i.e.