Study of injection molding pressure sensor with low cost and small probe

To improve the quality of the molding injection products, the process of injection needs to be monitored by measuring the instant pressure variation in the mold cavity with a small-size and erosion-resistant pressure sensor. In this study, bulk lead-zirconate-titanate (PZT) with reliable piezoelectric properties was used in sensors as pressure sensing elements. By taking advantage of micro-electrical-mechanical (MEM) technology, the sensing element can be fabricated with low cost and high performance. For the purpose of packaging, an isolation layer on the bulk PZT should be deposited by using RF sputtering. Since the surface roughness of electrode of the bulk PZT is too large to sputter an isolation layer of SiO₂ directly, instead, a layer of aluminum is deposited by using sputtering in advance. The results show the surface roughness of the electrode has been improved up to an acceptable range. After this, a series of process, such as, SiO₂ sputtering, lithography, etching and packaging are followed to complete the pressure sensing element and the pressure sensor. Some experiments are implemented to evaluate the performance of the packaged sensor. The results show that not only the static and dynamic response of the proposed sensor can compete with the similar products in the market, but also the cost and the probe size is far superior to that of existing pressure sensors.