US7036387
1. A printed circuit board (PCB) comprising:
a component footprint suitable for mounting an electronic component, the component footprint having a plurality of pads; and
a strain gage, wherein at least a portion of the strain gage is integrated into at least one layer internal to the PCB in the vicinity of the component footprint, wherein the strain gage includes at least one electrical conductor accessible on a surface of the PCB for resistance measurements.
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As noted above, strain gages may be mounted to a PCB in order to determine the amount of strain to which the PCB is subjected during the manufacturing process of an electronic assembly. FIG. 2 illustrates the mounting of strain gages on a PCB in the vicinity of a BGA footprint on the PCB. In the embodiment shown, strain gages are mounted on the PCB near each of the corners of a BGA footprint. More particularly, the strain gages may be attached to the PCB by the use of epoxy. Resistance measurements taken for each of the mounted strain gages may allow the approximation of the strain encountered on the PCB by the portion upon which the BGA is mounted. However, the locations of these strain gages, while close to the BGA footprint, are not ideal.
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Strain gages 20 are located within the layers of PCB 5 in the vicinity of footprint 25. One of the strain gages 20 is located under footprint 25 in its entirety. Another one of strain gages 20 is located partially under footprint 25. A third strain gage 20 is located in the vicinity of footprint 25, although no part of this strain gage is actually under footprint 25. The actual locations of strain gages 20 in various embodiments may be determined in part by considerations such as signal routing density or other constraints.
Footprint 25 is a footprint suitable for mounting a surface mount component package, such as a BGA. Other embodiments wherein footprint 25 is suitable for mounting other types of electronic component packages, such as a quad flat pack, are also possible and contemplated. Footprint 25 includes a plurality of pads （＊to抜け？）which conductive elements of the electronic component packaged may be attached by methods such as soldering.
（＊面積、領域というより部材？）
