Tsukahara Y, Nakaso N, Kushibiki J I, Chubachi N
Toppan Printing Co. Ltd., Saitama.
IEEE Trans Ultrason Ferroelectr Freq Control. 1989;36(6):638-42. doi: 10.1109/58.39114.
Layer thickness measurements with an acoustic micrometer using pseudo-Sezawa waves in which ultrasonic waves are obliquely applied to a layered surface of a specimen have been proposed. A case in which the plate thickness of the specimen is so thin that it cannot be regarded as a half space is studied. A number of modes of plate waves are then excited in addition to pseudo-Sezawa waves. The plate waves, giving rise to the appearance of extra dips in the power spectrum of reflected waves, cause difficulties in the measurements. To prevent the excitation of plate waves, it is proposed that a mask of a sound-insulating material with a slit aperture should be placed on the layered surface of the specimen. Experiments and theoretical calculations, using lead frames of LSI chips as typical test specimens with thin substrates, were performed to demonstrate the effectiveness of the present method in preventing the excitation of plate waves.
有人提出了一种使用声学测微计，利用伪塞扎瓦波（其中超声波倾斜地施加到试样的分层表面）来测量层厚度的方法。研究了试样的板厚非常薄以至于不能被视为半空间的情况。除了伪塞扎瓦波之外，还会激发许多板波模式。这些板波会在反射波的功率谱中产生额外的凹陷，给测量带来困难。为了防止板波的激发，建议在试样的分层表面放置一个带有狭缝孔径的隔音材料掩膜。使用LSI芯片的引线框架作为具有薄基板的典型测试试样进行了实验和理论计算，以证明本方法在防止板波激发方面的有效性。
