An advancement in electronic devices has promoted accelerations of clock signals used in electronic devices. When high-speed clock signals operate on a circuit board (e.g., a printed circuit board) in an electronic device, electromagnetic noises are generated and are emitted from the other electronic devices. Such electromagnetic noises may affect other electronic devices and may cause misoperations in those electronic devices. Accordingly, a regulation of the leakage amount of electromagnetic noises from electronic devices has been enforced, and electro-magnetic compatibility (EMC) countermeasures have been required in design and assembly steps of electronic devices.
Because electromagnetic noises can be blocked by conductors (e.g., metals), accommodating an electronic circuit that may become a source of electromagnetic noises in a sealed casing made of a metal is regarded as one EMC countermeasure. More specifically, respective flange sections are provided to two metal-made members to construct a casing, and flange sections of the two members are overlapped and then the two members are secured with screws, calking, rivets, welding, and the like (hereinafter referred to as “securing elements”) while maintaining the overlapping.
Patent Document 1: Japanese Registered Utility Model No. 3065107
Patent Document 2: Japanese Laid-open Patent Publication No. 2007-67195
Patent Document 3: Japanese Laid-open Patent Publication No. 2006-318416
Patent Document 4: Japanese Laid-open Patent Publication No. 2015-26173
An EMC countermeasure (also referred to as an electromagnetic noise countermeasure or shield countermeasure) as described above is started from a CAD (computer aided design) design phase of a product. In this case, whether leakage of electromagnetic noises can be controlled by an EMC countermeasure is verified using functions provided to CAD system. The verification is made by comparing the distance between securing elements described above in the flange sections (overlap sections), with a threshold for checking the distance between the securing elements. When the distance between the securing elements is equal to or smaller than the threshold, it is determined that a verification result is a pass. In contrast, the distance between the securing elements exceeds the threshold, it is determined that the verification result is a fail.
In this case, because the above-described threshold is set by a user, the leakage amount of electromagnetic noises may be deviated and a human task error may occur. Further, because the width of overlap sections (the sections at which flange sections overlap), which contributes to a reduction in the leakage amount of electromagnetic noises, is not taken into considerations, electromagnetic noises may leak from an electronic device during an actual operation of the electronic device even though a verification result has been determined as a pass.