System for inspection and testing of electrical circuits
Publication Date: 2002-Oct-27
The IP.com Prior Art Database
Shai ZOHAR: INVENTOR [+2]
A system & method for testing printed circuit boards comprises a boundary scan testing assembly for performing boundary scan testing on a printed circuit board and an automated optical inspection system (whether by visual light or by X-rays) for performing automated optical inspection on the printed circuit board. The system is configured such that the boundary scan testing assembly is operative to perform the boundary test on a printed circuit board in parallel to automated optical inspection thereof.
Optical Inspection System Including Boundary Scan
Field of Inventions.
The present invention relates to systems and methods for inspecting assuring the quality of populated electronic circuit boards, an more particularly to systems and methods employing automated optical inspection and boundary scan testing.
It is well known to employ systems for Automated Optical Inspection (AOI) for use in quality assurance programs. AOI is employed during the manufacture of printed circuit board substrates, as well as during various stages of adhering electronic components to printed circuit boards. AOI and AXI may analysis of images formed by reflectance of light by the surface of an a circuit board, the fluorescent stimulation by a scanned laser beam, X- ray irradiation or the like.
Moreover, it is known to test assembled printed circuit boards to assure desired electrical behavior and functionality. Electrical testing may include using bed of nails or flying probe testers, and/or boundary scan techniques. Functional testing may include boundary scan techniques as well, and electrical activation of powered-on board. As seen in Fig. 1, in conventional populated board manufacturing processes, AOI/AXI, electrical and functional testing stages of quality are performed entirely serially, and the electrical and functional testing are done beyond the SMT process.
Summary of the Inventions
(1) New Inspection and Testing Process
A new methodology for inspecting and testing populated printed circuit boards, as seen in Fig. 2, is proposed. In accordance with the new methodology, boundary scan testing is executed in parallel to inspection in an automated inspection system (whether by visual light or by X rays). Typically, the new methodology is used as part of a surface mount technology fabrication process.
(2) New AOI Machine, Contains Boundary Scan Capabilities
For the execution of the above-mentioned methodology for inspecting and testing populated printed circuit boards, a new AOI machine has been developed. The machine includes a first optical inspection functionality (visual light, fluorescence, X-ray etc.) and further includes suitable interconnection for simultaneously executing boundary scan procedures during optical inspection. A conceptual structure of such a machine is shown in Fig. 3.
Description of the Invention
(1) New Imaging and Testing Process
As seen in Fig. 2, the execution of a boundary scan (BS) procedures was moved into an SMT inspection process, following the reflow stage. The BS is executed, by the new process, on the same station used by prior art only for inspection. Accordingly, an optical inspection system is equipped with suitable circuitry for performing a boundary scan, or any other suitable functional testing procedure. Moreover, such testing, which is independent from, an substantially unaffected by optical inspection, utilizes the "dead- time" of optical inspection in order to complete a functio...