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US 5,307,139 AGranted
Apparatus and method for detecting leaks in packages
AssigneeLaser Technology, Inc.
InventorsJohn Tyson, II, John W. Newman
Life of this patent
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AssigneeLaser Technology, Inc.
InventorsJohn Tyson, II, John W. Newman
Estimating the term…
This invention detects leaks in small, hermetically sealed packages, especially microchips or other packages of electronic circuits. The invention includes a procedure for detecting fine leaks, and a somewhat different procedure for finding gross leaks. To detect gross leaks, one places the package in a chamber, and varies the pressure in the chamber slightly. If the leak is not too big, one wall of the package, such as its lid, initially becomes deformed, but quickly returns to its original position, due to the leak. If the leak is very large, the wall of the package may not move at all. The position of the wall is monitored with an interferometer, such as an electronic shearography apparatus. The movements of the wall show whether there is a gross leak. In the fine leak test, the package is placed in the chamber and the pressure is changed substantially, thus causing the walls of the package to deform. If there is a fine leak, a deformed wall gradually returns to its initial position. Preferably, the chamber is pressurized with helium to increase the sensitivity of the test. The gradual return of the deformed wall can be measured by the interferometer, and the rate at which the wall returns to its starting position can be used to calculate the leak rate. In another embodiment, a single pixel of a series of interferometric images is analyzed to determine the number of times the pixel changes from a maximum to a minimum and back to a maximum. The latter number is related to the number of wavelengths of deformation, and can be used to compute the leak rate of the package.
A method of inspecting a package for gross leaks, the method comprising the steps of:
A method of inspecting a package for gross leaks, the method comprising the steps of placing the package in a chamber, and varying the pressure in the chamber at a known rate, while simultaneously recording a series of interferometric images of a surface of the package, comparing said images with each other to determine how much the surface has moved, and determining whether the package is leaking by analyzing movement of said surface.
A method of inspecting a package for fine leaks, the method comprising the steps of:
A method of inspecting a package for leaks, the method comprising the steps of:
A method of inspecting a package for leaks, the method comprising the steps of placing the package in a chamber, varying the pressure in the chamber, generating a series of interferometric images of at least a portion of the surface, during an interval of time, each image including at least one pixel, determining the number of times that a given pixel changes from a maximum to a minimum to a maximum intensity, during said interval of time, using said number to determine the deformation of the surface during said interval, and determining whether the package is leaking by analyzing the deformation of said surface.
A method of determining the stiffness of a surface of a package, the method comprising the steps of:
A method of inspecting a pressurized package for leaks, the method comprising the steps of:
A method of measuring fine movements or deformations of a surface, the method comprising the steps of:
Dependencies are inferred from the claim text.