Optical inspection system for solder joints and inspection method

Claim 2

An optical inspection system comprising: positioning means for the locating of a soldering pad upon which lies a component lead which has been purportedly soldered thereon by concave fillets; an optical-electronic transducer defining an inspection axis, said optical-electronic transducer being positioned to receive an optical image along said axis, said optical-electronic transducer producing an electronic image signal; a non-polarized high intensity small diameter circular diffused fluorescent single-lamp light source positioned with respect to said positioning means and said axis, said single light source directing light toward said positioning means at an angle greater than 45 degrees with respect to said axis so that light from said light source is distributed evenly over a large area so as to eliminate shadows and specular reflections and said light strikes the pad at a low angle with respect to the pad so that top surfaces of the lead and the printed wiring board are comparatively dark relative to the light reflected from surfaces of said concave fillets, so that features of interest are distinct from back-ground and non-features; and means for digitizing the electronic image signal and means for analyzing the digitized image signal to evaluate the adequacy of the amount of fillet in the solder joint between the pad and the component lead by analyzing bands of said image signal to determine compliance to a rule which requires a continuous fillet along a predetermined portion of total potential fillet length.

Claim 3

The system of claim 1 wherein said optical-electronic transducer is a television camera.

Claim 4

The system of claim 2 wherein said television camera is positioned with its optical axis on said axis.

Claim 5

The system of claim 1 wherein said positioning means is a positioning table and said means for analyzing the digital image is connected to said positioning table so that when the analysis of a solder joint is complete, the positioning table moves to a position where a new pad and its component lead are on said axis.

Claim 6

The system of claim 4 wherein said positioning table is an X-Y table and said means for analyzing and evaluation the digitized image is connected to a control computer, said control computer being for recording the results of the analysis and for signaling movement of the X-Y table to a new position.

Claim 7

The system of claim 4 wherein said optical-electronic transducer is a television camera.

Claim 8

The system of claim 6 wherein said television camera is positioned with its optical axis on said axis.

Claim 9

An optical inspection system for solder joints comprising: a support for a printed wiring board having a surface with pads thereon and having components mounted on the printed wiring board and having component leads presumptively soldered to the pads on the printed wiring board with concave fillets, an axis substantially perpendicular to the pads, said support being a positioning table for holding thereon a printed wiring board with a plurality of pads, each having a component lead purportedly soldered thereto with a concave fillet; a television camera positioned substantially on said axis, said television camera being for optically observing solder pads and leads substantially on said axis to create an optical image thereof and converting the optical image to electronic image information; means for illuminating said support at said axis, said means for illumination comprising a single lamp high intensity, non-polarized diffuse low angle illumination about 15 degrees above the surface substantially around said axis with the angle being sufficiently low so that direct light reflection from the surface of the printed wiring board is not directed along said inspection axis and is distributed evenly over a large area so as to eliminate shadows and specular reflections; means for digitizing the electronic image information; means for analyzing the digitized image information for indicating the presence of solder fillets around the component lead to evaluate the adequacy of the solder joint between the component lead and the pad on the printed wiring board to produce a solder adequacy signal by analyzing bands of said digitized image to determine compliance to a rule which requires a continuous fillet along a predetermined portion of total potential fillet length; control computer means for recording the solder adequacy signal; and positioning table drive means connected to receive a signal from said control computer means for repositioning said table and the printed wiring board supported thereon to place another printed wiring board in position under said television camera for inspection.

Claim 10

An optical inspection system for solder joints comprising: a support for a printed wiring board having a surface with pads thereon and having components mounted on the printed wiring board and having component leads presumptively soldered to the pads on the printed wiring board with concave fillets, an axis substantially perpendicular to the pads, said support being a positioning table for holding thereon a printed wiring board with a plurality of pads, each having a component lead purportedly soldered thereto with a concave fillet; a television camera positioned substantially on said axis, said television camera being for optically observing solder pads and leads substantially on said axis to create an optical image thereof and converting the optical image to electronic image information; means for illuminating said support at said axis, said means for illumination comprising a single lamp high intensity, non-polarized diffuse low angle illumination about 15 degrees above the surface substantially around said axis with the angle being sufficiently low so that direct light reflection from the surface of the printed wiring board is not directed along said inspection axis and is distributed evenly over a large area so as to eliminate shadows and specular reflections; means for digitizing the electronic image information; means for analyzing the digitized image information for indicating the presence of solder fillets around the component lead to evaluate the adequacy of the solder joint between the component lead and the pad on the printed wiring board to produce a solder adequacy signal by analyzing bands of said digitized image to determine compliance to a rule which requires a continuous fillet along a predetermined portion of total potential fillet length; control computer means for recording the solder adequacy signal; and positioning table drive means connected to receive a signal from said control computer means for repositioning said table and the printed wiring board supported thereon to place another printed wiring board in position under said television camera for inspection.

Claim 11

The system of claim 8 wherein said means for illuminating is a circular fluorescent light positioned closely above said support to provide low angle about 15 degrees above the surface diffuse illumination substantially all the way around said axis.

Claim 12

The system of claim 9 wherein said support is a positioning table for holding thereon a printed wiring board with a plurality of pads, each having a component lead purportedly soldered thereto and upon receipt of a solder adequacy signal, said control computer signals said positioning table to move to place another pad on said axis.

Claim 15

The method of claim 11 further including repositioning the printed wiring board after the solder acceptance or rejection signal has been produced.

Claim 16

The method of claim 11 further including the preliminary step of positioning a printed wiring board having a plurality of pads thereon and having a corresponding plurality of component leads thereon; and repositioning the printed board to place a new pad for optical inspection when a solder acceptance or rejection signal is produced so as to automatically advance to any new inspection position.