Solder joint inspection features
A printed circuit board has a solder joint inspection system including a substrate surface having at least one solder pad thereon, at least one conductor wire having an end attached to the at least one solder pad, and a first inspection feature. A first inspection feature is marked on the substrate surface adjacent to the at least one solder pad to define a conductor end zone on the at least one solder pad. The end of the conductor wire is in the conductor end zone when properly attached. The at least one solder pad may define a second inspection feature to mark an extent to which the at least one solder pad is covered by a flow of solder when the wire is properly attached.
1 . A printed circuit board (PCB) comprising:
a substrate having a surface and at least one solder pad disposed on the substrate surface, the solder pad extending along an axial direction and having an axial length;
a slot formed through the substrate and extending through a distal end portion of the solder pad;
a magnet conductor wire routed through the slot and extending onto the solder pad from the distal end portion toward a proximal end portion of the solder pad, the magnet conductor wire having an end portion disposed on the solder pad, wherein insulation is removed from the end portion prior to placement on the solder pad;
a fiducial marking silkscreened on the substrate surface adjacent to the solder pad, the fiducial marking comprising a non-conductive ink physically separate from metallization of the solder pad, the fiducial marking extending along a transverse direction relative to the axial direction of the solder pad and having an axial length that is less than the axial length of the solder pad;
wherein the fiducial marking is positioned such that the fiducial marking is visually transposed onto the solder pad by projection along the transverse direction to define a contiguous bounded conductor end zone on the solder pad, the conductor end zone being axially spaced from the slot and defining a minimum required axial overlap length of the end portion of the magnet conductor wire on the solder pad; and
wherein the end portion of the magnet conductor wire is positioned entirely within the conductor end zone prior to soldering.
2 . The printed circuit board of claim 1 , wherein the solder pad defines a pair of opposed notches recessed inward from opposing lateral sides of the solder pad at a common axial location between the distal end portion and the proximal end portion, the opposed notches defining a narrowed region of the solder pad that establishes a solder flow boundary, wherein the narrowed region defines a visible axial boundary of solder coverage relative to the distal end portion.
3 . The printed circuit board of claim 2 , wherein the solder pad includes a first lateral width at the proximal end portion and a second reduced lateral width at the narrowed region defined by the opposed notches, each notch being recessed inward by a distance sufficient to define the reduced lateral width.
4 . The printed circuit board of claim 1 , wherein the fiducial marking comprises a silkscreened non-conductive ink layer deposited on the substrate surface and having a contrasting color relative to the solder pad and substrate surface to enhance visual detection of the bounded conductor end zone prior to soldering.
5 . The printed circuit board of claim 1 , wherein the PCB includes a plurality of said solder pads, each solder pad including a respective slot and a respective fiducial marking positioned to define a corresponding conductor end zone, the conductor end zones being aligned along a common axial reference direction across the PCB wherein the PCB.
6 . The printed circuit board of claim 1 , wherein the magnet conductor wire is preformed to include a bend at a location adjacent to the slot such that, after routing through the slot, the magnet conductor wire lies flush against the substrate surface along the axial direction of the solder pad prior to soldering.
7 . A printed circuit board (PCB) comprising:
a substrate having a surface;
a solder pad formed as a single continuous metallized region on the substrate surface and extending along an axial direction from a proximal end portion to a distal end portion, the solder pad having a first lateral width measured transverse to the axial direction and defining a longitudinal centerline extending along the axial direction;
a slot formed through the substrate at the proximal end portion;
a magnet conductor wire routed through the slot and extending onto the solder pad from the proximal end portion toward the distal end portion; and
a pair of opposed notches formed in and recessed inward from opposing lateral sides of the solder pad at a common axial location between the proximal end portion and the distal end portion and symmetrically disposed about the longitudinal centerline,
wherein:
the opposed notches define a transverse constriction region of the solder pad having a second lateral width that is less than the first lateral width,
the transverse constriction region extends between the opposing lateral sides of the solder pad and is positioned between ten percent and fifty percent of the axial length of the solder pad measured from the proximal end portion, and
the transverse constriction region defines a visible axial boundary of solder coverage for visual inspection of solder flow from the proximal end portion toward the distal end portion.
8 . The printed circuit board of claim 7 , wherein each of the opposed notches has a concave arcuate profile defining a continuous reduction in lateral width from the first lateral width to the second lateral width.
9 . The printed circuit board of claim 7 , wherein each notch is recessed inward from the respective lateral side by a depth sufficient to reduce the lateral width of the solder pad by at least ten percent relative to the first lateral width.
10 . The printed circuit board of claim 7 , wherein the opposed notches are aligned across the solder pad at the common axial location located at forty percent of the axial length of the solder pad measured from the proximal end portion.
11 . A printed circuit board (PCB) comprising:
a substrate having a surface;
a solder pad formed as a single continuous metallized region on the substrate surface and extending along an axial direction from a proximal end portion to a distal end portion, the solder pad having an axial length and a first lateral width measured transverse to the axial direction and defining a longitudinal centerline extending along the axial direction;
a slot formed through the substrate at the proximal end portion;
a magnet conductor wire routed through the slot and extending onto the solder pad from the proximal end portion toward the distal end portion, the magnet conductor wire having an end portion disposed on the solder pad;
a fiducial marking formed on the substrate surface adjacent to the solder pad, the fiducial marking extending along a transverse direction relative to the axial direction of the solder pad and having an axial length less than the axial length of the solder pad, the fiducial marking being positioned such that the fiducial marking is visually transposed onto the solder pad to define a bounded conductor end zone on the solder pad; and
a pair of opposed notches formed in and recessed inward from opposing lateral sides of the solder pad at a common axial location between the proximal end portion and the distal end portion and symmetrically disposed about the longitudinal centerline of the solder pad,
wherein:
the bounded conductor end zone is located axially spaced from the slot and defines an axial overlap region for positioning the end portion of the magnet conductor wire on the solder pad prior to soldering;
the opposed notches define a transverse constriction region of the solder pad having a second lateral width that is less than the first lateral width;
the transverse constriction region is located between about thirty percent and about fifty percent of the axial length of the solder pad measured from the proximal end portion; and
the transverse constriction region defines a visible axial boundary of solder coverage for inspection of solder extending from the proximal end portion toward the distal end portion.
12 . The printed circuit board of claim 11 , wherein each of the opposed notches has a concave arcuate profile defining a continuous reduction in lateral width from the first lateral width to the second lateral width.
13 . The printed circuit board of claim 11 , wherein each notch is recessed inward from the respective lateral side by a depth sufficient to reduce the lateral width of the solder pad by at least ten percent relative to the first lateral width.
14 . The printed circuit board of claim 11 , wherein the opposed notches are aligned across the solder pad at the common axial location located between about thirty percent and about fifty percent of the axial length of the solder pad measured from the proximal end portion.
15 . The printed circuit board of claim 11 , wherein the fiducial marking comprises a non-conductive ink layer deposited on the substrate surface and providing a contrasting optical appearance relative to the solder pad and the substrate surface to enhance visual inspection of the bounded conductor end zone.