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Sensor packaging for miniaturized silicon strain gauges

Yang, Weiyan (2017):
Sensor packaging for miniaturized silicon strain gauges.
TU Darmstadt, [Master Thesis]

Abstract

Force sensing under small operation places in millimeter scale is strongly required in medical instruments. A highly-miniaturized force sensing element including electrical circuits is demanded. In addition, a high sensitivity is required to detect the small interaction between robot and cell tissues. In this master thesis, the packaging of a force sensing element as shown in Figure 1 and the characterization of the packaged sample are presented. The element is an integrated full-bridge silicon strain gauge measurement chip with the maximal side length 1.8 mm, which is manufactured by the research institute CiS GmbH (Erfurt, Germany). The chip is bonded on a steel substrate (stainless steel 1.4310 from Stahl-Becker GmbH, Heusenstamm, Germany). A flexible PCB with the maximal length 2 cm is connected to transmit the electrical signal. Potential problems by different mechanical and electrical bonding methods are analyzed. Defects and basic resistances of the strain gauge chip are measured and calculated. Glass frit bonding as one of the selected mechanical bonding technique is attempted by equipment at the institute EMK. Although different thermal curves, heating and cooling processes are tested, all samples suffer mechanical and electrical defects. The so-called flip chip soldering with adhesive bonding as another selected packaging method is discussed. Flip chip without and with underfill as a protection of electrical bonding are compared. In the experiment of flip chip with underfill, different solder pastes, underfill materials and underfill sequences are tested one-by-one. Mechanical and electrical defects are shown. Afterwards, an underfill method with the highest successful rate is selected. Corresponding samples are bonded on the substrate with different adhesives. After adhesive bonding, six finished samples are characterized. Load-on samples are tested under constant room temperature and rising temperature on a four-point bending platform. No-load samples are tested in a thermal chamber. Characteristics of the sample such as thermal output, sensitivity, zero offset error, linear error and hysteresis error in different packaging conditions are compared. Finally, a recommended packaging process for an application of high sensitivity and moderate thermal independence is presented as the result of this thesis.

Item Type: Master Thesis
Erschienen: 2017
Creators: Yang, Weiyan
Title: Sensor packaging for miniaturized silicon strain gauges
Language: English
Abstract:

Force sensing under small operation places in millimeter scale is strongly required in medical instruments. A highly-miniaturized force sensing element including electrical circuits is demanded. In addition, a high sensitivity is required to detect the small interaction between robot and cell tissues. In this master thesis, the packaging of a force sensing element as shown in Figure 1 and the characterization of the packaged sample are presented. The element is an integrated full-bridge silicon strain gauge measurement chip with the maximal side length 1.8 mm, which is manufactured by the research institute CiS GmbH (Erfurt, Germany). The chip is bonded on a steel substrate (stainless steel 1.4310 from Stahl-Becker GmbH, Heusenstamm, Germany). A flexible PCB with the maximal length 2 cm is connected to transmit the electrical signal. Potential problems by different mechanical and electrical bonding methods are analyzed. Defects and basic resistances of the strain gauge chip are measured and calculated. Glass frit bonding as one of the selected mechanical bonding technique is attempted by equipment at the institute EMK. Although different thermal curves, heating and cooling processes are tested, all samples suffer mechanical and electrical defects. The so-called flip chip soldering with adhesive bonding as another selected packaging method is discussed. Flip chip without and with underfill as a protection of electrical bonding are compared. In the experiment of flip chip with underfill, different solder pastes, underfill materials and underfill sequences are tested one-by-one. Mechanical and electrical defects are shown. Afterwards, an underfill method with the highest successful rate is selected. Corresponding samples are bonded on the substrate with different adhesives. After adhesive bonding, six finished samples are characterized. Load-on samples are tested under constant room temperature and rising temperature on a four-point bending platform. No-load samples are tested in a thermal chamber. Characteristics of the sample such as thermal output, sensitivity, zero offset error, linear error and hysteresis error in different packaging conditions are compared. Finally, a recommended packaging process for an application of high sensitivity and moderate thermal independence is presented as the result of this thesis.

Uncontrolled Keywords: silicon strain gauge, sensor packaging, flip-chip, glas frit bonding, miniaturized sensors
Divisions: 18 Department of Electrical Engineering and Information Technology > Institute for Electromechanical Design
18 Department of Electrical Engineering and Information Technology > Institute for Electromechanical Design > Measurement and Sensor Technology
18 Department of Electrical Engineering and Information Technology
Date Deposited: 10 Apr 2017 12:33
Referees: Kupnik, Prof. Mario
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