Development of a Oxygen Sensor for Marine ... - DTU Nanotech

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50 CHAPTER 6. PROBLEMS AND SOLUTIONS Figure 6.1: Picture of the wirebonder used to attach the wire to the chip and the flex print. wiring bonding is not possible to tin. Also people in the industry have suggested that the Au layer on the chip might have been to thin, and should be increased to 10k ˚A(it was 3000 ˚A), however others at MIC have successfully bonded to this thickness before. However this was only discovered late in the project, so some other way of connecting the chip and the flex print had to be found at the time. 6.1.1 Conducting Glue As is often the case the simplest solution is also the most viable, in this case a conducting glue. 1 While it may look and sound less refined than a a metal wire, it is relatively easy to apply with the tip of a needle dipped in the glue. That is if as long as some distance exists between the output electrodes. The glue used is, like most glues, somewhat viscous and hence if the output electrodes are to close to each other, it can be very hard if not impossible to 1 The glue is a conductive paste (H9807) from Namics, viscosity: 20 P a · s, V olumeresistivity : 0.7 × 10 −4 Ω · cm
6.1. WIREBONDING 51 make a line between the chip and the flex print without a short circuit being created. So while the conducting glue is a possible solution, it should only be considered a temporary solution. Figure 6.2: One of the chips with the silver colored electric glue on, as can be seen by comparing the left and the right side, there is a decent amount of distance between the output electrodes (left) for the Clark Sensor. While the output electrodes (right) of the temperature sensor is closer and harder to connect to with the conducting glue. Figure 6.3: Closeup of the design, the arrows point towards the platinum line that will cause the short circuit. While the conducting glue was a very viable solution one minor problem had to be overcome first. In order to make the wafer easier to dice, the chip design (as seen in Chapter 4 had a platinum line near the edge, see picture 6.3, which if the conducting glue was just put on as it were, would work as a short circuit, hence a small procedure was developed to apply the glue. This procedure was as follows: 1. Put a piece of ordinary tape over the sensor, to prevent it from being covered with glue, leaving roughly half of the output electrodes free.
Page 1 and 2:
Development of a Oxygen Sensor for
Page 3:
Abstract This thesis described the
Page 7 and 8:
Contents 1 Introduction 1 1.1 Disso
Page 9 and 10: CONTENTS vii B Fabrication Process
Page 11 and 12: Chapter 1 Introduction Roughly 70 %
Page 13 and 14: 1.1. DISSOLVED OXYGEN LEVEL 3 K = a
Page 15 and 16: 1.2. THESIS OUTLINE 5 In Chapter 8
Page 17 and 18: Chapter 2 Optodes and ISFET There a
Page 19 and 20: 2.2. ISFET (ION SELECTIVE FIELD EFF
Page 21 and 22: 2.3. SUMMARY 11 of oxygen molecules
Page 23 and 24: Chapter 3 Theory of the Clark Senso
Page 25 and 26: 3.1. CHEMISTRY OF THE CLARK SENSOR
Page 33 and 34: 3.2. THE POTENTIOSTAT 23 Reference
Page 35 and 36: 3.2. THE POTENTIOSTAT 25 Working El
Page 37 and 38: Chapter 4 System Design The sensor
Page 39 and 40: 4.2. ACTUAL DESIGN 29 seen on figur
Page 41 and 42: 4.2. ACTUAL DESIGN 31 The third des
Page 43 and 44: 4.3. TEMPERATURE SENSOR 33 Figure 4
Page 45 and 46: 4.3. TEMPERATURE SENSOR 35 a Pt300,
Page 47 and 48: 4.4. PACKAGING 37 Figure 4.11: Clos
Page 49 and 50: 4.4. PACKAGING 39 90 mm 15 mm 6 mm
Page 51 and 52: Chapter 5 Fabrication The fabricati
Page 53 and 54: 5.1. PROCESSING 43 Figure 5.4: Alig
Page 55 and 56: 5.2. BACK-END PROCESSING 45 under e
Page 57 and 58: 5.2. BACK-END PROCESSING 47 5.2.2 A
Page 59: Chapter 6 Problems and Solutions In
Page 63 and 64: 6.2. THE FLEX PRINT 53 The reason b
Page 65 and 66: 6.3. THE ’O’-RING 55 Figure 6.8
Page 67 and 68: Chapter 7 Evaluation of Results and
Page 69 and 70: 7.2. TEMPERATURE SENSOR 59 Figure 7
Page 71 and 72: 7.4. SUMMARY 61 Figure 7.5: Polarog
Page 73 and 74: Chapter 8 Conclusion The primary go
Page 75 and 76: Bibliography [1] http://earthobserv
Page 77 and 78: BIBLIOGRAPHY 67 [26] W.E. Morf. The
Page 79 and 80: Appendix A Silicide Recipe The foll
Page 81 and 82: Appendix B Fabrication Process 71
Page 84 and 85: 74 APPENDIX B. FABRICATION PROCESS
Page 86: 76 APPENDIX C. PROCESS SEQUENCE
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