Method and apparatus for detecting excess/insufficient solder defects

A method of detecting an excess solder defect comprising the steps of:

• producing a cross-sectional image of a cutting plane of a solder joint;
• analyzing said cross-sectional image to determine the thickness of a portion of said solder joint;
• defining an upper solder thickness threshold value;
• and
• comparing said thickness to said upper threshold value.

A method of measuring the thickness of connective material forming an electrical connection, said method comprising the steps of:

• exposing said connective material to a source of transmissive energy;
• detecting the intensity of said transmissive energy which passes through said material;
• producing a cross-sectional image of a cutting plane of said material with said detected energy;
• defining a region of said cross-sectional image corresponding to a region of said material wherein the thickness of said material is to be determined;
• calculating an average image intensity for said region and
• comparing said average image intensity to a calibration standard which correlates image intensity with material thickness.

An apparatus for measuring the thickness of material forming an electrical connection comprising:

• an imaging system for producing a cross-sectional image of a cutting plane of an electrical connection;
• and
• an image analysis system for analyzing said cross-sectional image to determine the thickness of said material, said image analysis system further comprising:
• means for defining a region of said cross-sectional image corresponding to a region of said material wherein the thickness of said material is to be determined;
• a processor for calculating an average image intensity value for said region;
• and
• a comparator for comparing said average image intensity value to a calibration standard having a correlation between image intensity and material thickness to obtain the thickness of said material forming said electrical connection.

A method of detecting a defect in a solder joint comprising the steps of:

• producing a cross-sectional image of said solder joint wherein said image displays features of said solder joint against a background;
• dividing said cross-sectional image into a pixel grid wherein each of said pixels in said grid has an image intensity value which corresponds to the intensity of said image at the location of said pixel;
• defining a region of interest;
• determining a background image intensity value of said cross-sectional image, said determining step further including the steps of:
• defining a background region;
• and
• calculating an average background value;
• subtracting said average background value from the image intensity values of each pixel comprising said region of interest to create a set of background-corrected image intensity values for the pixels comprising said region of interest;
• calculating an average of said background-corrected image intensity values for the pixels comprising said region of interest;
• providing a calibration standard which correlates image intensity value with solder thickness value;
• and
• comparing said average of said background-corrected image intensity value within said region of interest to said calibration standard to determine an average solder thickness value for said region of interest.

A method for monitoring and controlling a solder application apparatus which forms solder joints, said method comprising the steps of:

• producing cross-sectional images of cutting planes of a plurality of solder joints;
• determining the thickness of each of said plurality of solder joints;
• comparing said determined solder thickness with a nominal solder thickness;
• generating a feedback signal in response to said comparison;
• and
• providing said feedback signal to said solder application device.

A method for determining, in a digital cross-sectional image of a circuit board, the centroid of an image feature having a predetermined shape, said method comprising the steps of:

• defining a pixel template having an inner region, an outer region and a reference pixel;
• wherein said inner region is of substantially the same shape as said image feature and said outer region substantially surrounds said inner region;
• creating a centroid image having a one to one pixel correlation with a portion of said circuit board image containing said image feature, said creating step further comprising the steps of:
• a) superimposing said template on said portion of said circuit board image;
• b) summing the image intensity values of pixels comprising said circuit board image falling within said inner region of said template;
• c) summing the image intensity values of said digital image falling within said outer region of said template;
• d) taking the difference of said inner region sum and said outer region sum;
• e) defining the intensity of a pixel of said centroid image corresponding to said template reference pixel to be equal to said difference;
• and
• f) repeating steps a) through e) until a substantial number of the pixels comprising said portion of said circuit board image have bee covered by said template reference pixel;
• comparing the image intensity values of the pixels comprising said centroid image to locate the pixel having the maximum value;
• and
• defining a pixel of said circuit board image corresponding to said maximum value pixel of said centroid image to be the location of the centroid of said image feature.

An apparatus for measuring the thickness of material forming an electrical connection comprising:

• an imaging system for producing a cross-sectional image of an electrical connection;
• an image analysis system for analyzing said cross-sectional image to determine the thickness of said material, said image analysis system further comprising:
• means for defining a region of said cross-sectional image corresponding to a region of said material wherein the thickness of said material is to be determined;
• a processor for calculating an average image intensity value for said region;
• a means for subtracting a first correction factor from said average image intensity value and setting the resulting difference equal to a first corrected intensity value;
• a means for multiplying said first corrected intensity value by a second correction factor, said product equal to a second corrected intensity value;
• and
• a comparator for comparing said second corrected intensity value to a calibration standard having a correlation between image intensity value and material thickness.

A method of measuring the thickness of material forming a subject electrical connection comprising the steps of:

• producing a cross-sectional image of said subject electrical connection;
• analyzing said cross-sectional image to determine the thickness of said material, said analyzing step further comprising the steps of:
• defining a region of said cross-sectional image corresponding to a region of said material wherein the thickness of said material is to be determined;
• calculating an average image intensity value for said region;
• subtracting a first correction factor from said average image intensity value and setting the resulting difference equal to a first corrected intensity value;
• multiplying said first corrected intensity value by a second correction factor, said product equal to a second corrected intensity value;
• and
• comparing said second corrected intensity value to a calibration standard having a correlation between image intensity value and material thickness.

A method of measuring the volume of connective material forming an electrical connection, said method comprising the steps of:

• exposing said connective material to a source of transmissive energy;
• detecting the intensity of said transmissive energy which passes through said material;
• producing a cross-sectional image of said material with said detected energy;
• defining a region of said cross-sectional image corresponding to a region of said material wherein the volume of said material is to be determined, said region having a predetermined area;
• calculating an average image intensity for said region;
• comparing said average image intensity to a calibration standard which correlates image intensity with material thickness to obtain an average thickness measurement value over said region of interest;
• and
• multiplying said obtained average thickness measurement value by said predetermined area of said region of interest to obtain the volume of said connective material.

An apparatus for measuring the volume of material forming an electrical connection comprising:

• an imaging system for producing a cross-sectional image of a cutting plane of an electrical connection;
• and
• an image analysis system for analyzing said cross-sectional image to determine the volume of said material, said image analysis system further comprising:
• means for defining a region of said cross-sectional image corresponding to a region of said material wherein the volume of said material is to be determined, said region having a predetermined area;
• a processor for calculating an average image intensity value for said region;
• a comparator for comparing said average image intensity value to a calibration standard having a correlation between image intensity and material thickness;
• and
• a multiplier for calculating the volume of said connective material within said region of interest using said material thickness and said predetermined area.

An apparatus for measuring the thickness of material forming an electrical connection comprising:

• an imaging system for producing a cross-sectional image of a cutting plane of an electrical connection;
• and
• an image analysis system for analyzing said cross-sectional image to determine the thickness of said material, said image analysis system further comprising:
• a processor for calculating an average image intensity value for a region of said cross-sectional image corresponding to a region of said material wherein the thickness of said material is to be determined;
• and
• a comparator for comparing said average image intensity value to a calibration standard having a correlation between image intensity and material thickness.

An apparatus for monitoring and controlling a solder application device which forms solder joints, said apparatus comprising:

• a solder joint inspection device which determines the thickness of each of said solder joints wherein said solder joint inspection device comprises:
• an imager that produces cross-sectional images of cutting planes of solder joints;
• and
• an image analyzer which analyzes said cross-sectional images to determine the thickness of each of said solder joints;
• a comparator which compares said determined solder thickness with a nominal solder thickness and provides an output comparison value;
• and
• a controller which receives as input said comparison value and generates a feedback signal which causes said solder application device to increase or reduce the amount of solder deposited onto said solder joints.

An apparatus for measuring the thickness of material forming an electrical connection comprising:

• an imaging system for producing a cross-sectional image of an electrical connection;
• and
• an image analysis system for analyzing said cross-sectional image to determine the thickness of said material, said image analysis system further comprising:
• a processor that calculates an average image intensity value for a region of said cross-sectional image corresponding to a region of said material wherein the thickness of said material is to be determined, said processor further comprising a subtractor which subtracts a first correction factor from said average image intensity value and sets the resulting difference equal to a first corrected intensity value, said processor further comprising a multiplier which multiplies said first corrected intensity value by a second correction factor and sets the resulting product equal to a second corrected intensity value;
• and
• a comparator that compares said second corrected intensity value to a calibration standard having a correlation between image intensity and material thickness to obtain said material thickness.

An apparatus for measuring the volume of material forming an electrical connection comprising:

• an imaging system for producing a cross-sectional image of a cutting plane of an electrical connection;
• and
• an image analysis system for analyzing said cross-sectional image to determine the volume of said material, said image analysis system further comprising:
• a processor that calculates an average image intensity value for a region of said cross-sectional image corresponding to a region of said material wherein the volume of said material is to be determined, said region having a predetermined area, said processor further comprising a comparator that compares said average image intensity value to a calibration standard having a correlation between image intensity and material thickness, said processor further comprising a multiplier that calculates the volume of said connective material within said region of interest using said material thickness and said predetermined area.

A method of detecting an insufficient solder defect comprising the steps of:

• producing a cross-sectional image of a cutting plane of a solder joint;
• analyzing said cross-sectional image to determine the thickness of a portion of said solder joint, said analyzing step further comprising the steps of:
• defining a region of interest on said image;
• partitioning said region of interest into a grid of pixels;
• assigning an image intensity value to each of said pixels wherein said image intensity value corresponds to the intensity of the portion of the image represented by each of said pixels;
• calculating an average image intensity value of the pixels within said region of interest;
• and
• correlating said average image intensity value with a calibration standard;
• defining a lower solder thickness threshold value;
• and comparing said thickness to said lower threshold value.

A method of detecting an excess solder defect comprising the steps of:

• producing a cross-sectional image of a cutting plane of a solder joint;
• analyzing said cross-sectional image to determine the thickness of a portion of said solder joint, said analyzing step further comprising the steps of:
• defining a region of interest on said image;
• partitioning said region of interest into a grid of pixels;
• assigning an image intensity value to each of said pixels wherein said image intensity value corresponds to the intensity of the portion of the image represented by each of said pixels;
• calculating an average image intensity value of the pixels within said region of interest;
• and
• correlating said average image intensity value with a calibration standard;
• defining an upper solder thickness threshold value;
• and comparing said thickness to said upper threshold value.