Method and apparatus for detecting excess/insufficient solder defects
US5291535A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 5, 1991 |
| Grant date | Mar 1, 1994 |
| Priority date | — |
| Expiry date | Aug 5, 2011 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01R31/304
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method and apparatus for the detection of excess or insufficient solder conditions at electrical connections on printed circuit boards are disclosed. The invention analyzes a cross-sectional image of an electrical connection to obtain the average solder thickness of the connection. This average solder thickness is then compared to an upper threshold value to determine if the connection is an excess solder defect, and a lower threshold value to determine if the connection is an insufficient solder defect. In one embodiment, the present invention compensates for variations in image intensity due to the background by employing a first and second correction factor in the calibration technique. The first correction factor is the measured background gray scale value local to the connection, while the second correction factor is determined to have a substantially linear relationship to the background image intensity local to each solder connection. The present invention further includes a process control feedback system which detects and compensates for trends in the solder application process. This helps to insure that defective solder joints are avoided before they are produced. In on…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.