Abstract:
An instant response pressure sensor is disclosed. An embodiment shows no continuous gap is configured between a piezoresistor and neighboring element(s) in thickness direction. The instant response pressure sensor is able to respond immediately to an extremely small pressure applied thereupon in the early stage with an extremely small distance movement because the instant response pressure sensor without having an extra press journey to move before trigging.

Description:
BACKGROUND 
     Technical Field 
     The present invention relates to a pressure sensor, especially an instant response pressure sensor which does not have any extra press journey before triggering a signal corresponding to an extremely small pressure applied against it due to the fact that the disclosed structure does without having a continuous gap between a piezoresistor and a neighboring element in the thickness direction. 
     Description of Related Art 
       FIG. 1  shows a prior art pressure sensor which has a top substrate  10 T. A top electrode  11 T is configured on a bottom side of the top substrate  10 T; a top piezoresistor  12 T is configured on a bottom side of the top electrode  11 T. A bottom piezoresistor  12 B is configured under the top piezoresistor  12 T while keeping a continuous space or gap  16  therebetween; and a bottom electrode  11 B is configured on a bottom side of the bottom piezoresistor  12 B. A bottom substrate  10 B is configured on a bottom side of the bottom electrode  11 B. 
       FIG. 2  shows an operation of the prior art 
       FIG. 2A  shows that the pressure sensor displays a current I 0  which is zero ampere (I 0 =0), and a resistance R 0  which is infinity (R 0 =∞) before the pressure sensor is depressed. At this moment, the bottom surface of the top piezoresistor  12 T is shown at a position P 0 . 
       FIG. 2B  shows that the pressure sensor displays a current I 1  which is zero ampere (I 1 =0) and a resistance R 1  which is infinity (R 1 =∞) when it is depressed initially to a status just offset the continuous gap  16  between the two piezoresistors  12 T,  12 B. In other words, the pressure sensor is depressed at a position where the top piezoresistor  12 T just touches the bottom piezoresistor  12 B. At this moment, the bottom surface of the top piezoresistor  12 T is shown at a position P 1 . 
       FIG. 2C  shows that the pressure sensor displays a current I 2  which is larger than zero ampere (I 2 &gt;0) and a measurable resistance R 2  displayed when it is depressed further more. In other words, the pressure sensor is depressed further more than the position it was as shown in  FIG. 2B . At this moment, the bottom surface of the top piezoresistor  12 T is at a position P 2 . 
       FIG. 3  shows Resistance v. Press Journey for the prior art 
       FIG. 3  shows that the Y-axis shows Resistance, and the X-axis shows Press Journey. Either the resistance R 0  or R 1  of the prior art device is infinity when the bottom surface of the top piezoresistor  12 T is at a position of either P 0  or P 1 . The resistance of the prior art device is R 2  when the bottom surface of the top piezoresistor  12 T is at a position of P 2  which is a trigger position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a prior art 
         FIG. 2  shows an operation of the prior art 
         FIG. 3  shows Resistance v. Press Journey for the prior art 
         FIGS. 4A ˜ 4 B show a first embodiment according to the present invention 
         FIGS. 5A ˜ 5 C show an operation of the first embodiment 
         FIG. 6  shows Resistance v. Press Journey for the first embodiment 
         FIG. 7  shows a comparison of the electric characteristics between the present invention and the prior art 
         FIGS. 8A ˜ 8 B show a second embodiment according to the present invention 
         FIG. 9  shows an operation of the second embodiment 
         FIGS. 10A ˜ 10 B show a third embodiment according to the present invention 
         FIG. 11  shows an operation of the third embodiment 
         FIGS. 12A ˜ 12 B show a fourth embodiment according to the present invention 
         FIG. 13  shows an operation of the fourth embodiment 
         FIGS. 14A ˜ 14 B show a fifth embodiment according to the present invention 
         FIG. 15  shows an operation of the fifth embodiment 
         FIG. 16  shows a first application of the pressure sensor according to the present invention 
         FIG. 17  shows a second application of the pressure sensor according to the present invention 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention discloses an instant response pressure sensor which senses extremely small pressures applied against the sensor. The feature of early response makes it suitable for being used as an immediate sensor such as a pressure sensitive electronic pen, or a pressure sensitive volume button for an electronic apparatus . . . etc. 
       FIGS. 4A ˜ 4 B show a first embodiment according to the present invention. 
       FIG. 4A  shows a first embodiment of an instant response pressure sensor which has a top substrate  10 T, a top electrode  11 T configured on a bottom side of the top substrate  10 T, a top piezoresistor  12 T configured on a bottom side of the top electrode  11 T, a bottom piezoresistor  12 B configured under the top piezoresistor  12 T, a bottom electrode  11 B configured on a bottom side of the bottom piezoresistor  12 B, and a bottom substrate  10 B configured on a bottom side of the bottom electrode  11 B. A top surface of the bottom piezoresistor  12 B is configured to contact a bottom surface of the top piezoresistor  12 T with an infinite resistance therebetween before a pressure is applied against the pressure sensor. 
       FIG. 4B  shows an interface between the top piezoresistor and the bottom piezoresistor. A bottom surface of the top piezoresistor  12 T is rugged in a microscopic view, and a top surface of the bottom piezoresistor  12 B is also rugged in a microscopic view, therefore partial area contacts  121  exist therebetween and an infinite resistance is displayed therebetween due to extremely small area contact. 
       FIGS. 5A ˜ 5 C show an operation of the first embodiment 
       FIG. 5A  shows that the pressure sensor displays a current I 0  which is zero ampere (I 0 =0) and a resistance R 0  which is infinity (R 0 =∞) before it is depressed. At this moment, the bottom surface of the top piezoresistor  12 T is shown at a position P 0 . 
       FIG. 5B  shows that the pressure sensor displays a current I 1  which is larger than zero ampere (I 1 &gt;0), a measurable resistance R 1  is displayed which is smaller than R 0  (R 1 &lt;R 0 ) when the pressure sensor is depressed initially. In other words, the pressure sensor is lightly depressed and at this moment, the bottom surface of the top piezoresistor  12 T is shown at a position P 1 . 
       FIG. 5C  shows that the pressure sensor displays a current I 2  larger than the current I 1  (I 2 &gt;I 1 ), a measurable resistance R 2  is displayed which is smaller than R 1  (R 2 &lt;R 1 ) when it is depressed further more. In other words, the pressure sensor is depressed heavier than the position it was as shown in  FIG. 5B . At this moment, the bottom surface of the top piezoresistor  12 T is at a position P 2 . 
       FIG. 6  shows Resistance v. Press Journey for the first embodiment 
       FIG. 6  shows that the resistance R 0  of the first embodiment is infinity when the bottom surface of the top piezoresistor  12 T is at a position P 0 . The resistance R 1  is displayed for the first embodiment when the bottom surface of the top piezoresistor  12 T is depressed at a position P 1 . Referring to  FIG. 6  a trigger position Px for the first embodiment can be found in between position P 0  and P 1 , namely P 0 &lt;Px&lt;P 1 , and a corresponding resistance Rx can be detected for the trigger position Px, where ∞&gt;Rx&gt;R 1 . 
       FIG. 7  shows a comparison of the electric characteristics between the present invention and the prior art. A left lower curve shows the electric characteristics for the present invention. A right upper curve shows the electric characteristics for the prior art. Under similar operation, the present invention has a trigger position at Px and the prior art has a trigger position at P 2 ; where P 2 &gt;Px. That means the present invention can trigger very earlier than a prior art. Correctly to say, the present invention triggers at the very beginning when a pressure applied against the pressure sensor, even an extremely small pressure is applied. Meanwhile, the press journey is extremely small before trigging. 
       FIGS. 8A ˜ 8 B show a second embodiment according to the present invention 
       FIG. 8A  shows that an instant response pressure sensor has a top electrode  11 T; a piezoresistor  12 T is configured on a bottom side of the top electrode  11 T; a bottom electrode  11 B is configured under the piezoresistor  12 T; wherein the piezoresistor  12 T contacts the bottom electrode  11 B with an infinite resistance before a pressure applied against the pressure sensor, where I=0. A top substrate  10 T is configured on a top side of the top electrode  11 T, and a bottom substrate  10 B is configured on a bottom side of the bottom electrode  11 B. 
       FIG. 8B  shows an interface between the piezoresistor and the bottom electrode 
     Since a bottom surface of the piezoresistor  12 T is rugged in a microscopic view so that partial area contacts exist to maintain an infinite resistance between the piezoresistor and the bottom electrode. 
       FIG. 9  shows an operation of the second embodiment 
       FIG. 9  shows that a current I passes through the top electrode  11 T, the piezoresistor  12 T and the bottom electrode  11 B when a pressure is applied against the pressure sensor, where I&gt;0. 
       FIGS. 10A ˜ 10 B show a third embodiment according to the present invention 
       FIG. 10A  shows that an instant response pressure sensor has a top electrode  11 T; a piezoresistor  12 B is configured under a bottom side of the top electrode  11 T; wherein the top electrode  11 T contacts the piezoresistor  12 B with an infinite resistance before a pressure applied against the pressure sensor, where I=0; a bottom electrode  11 B is configured on a bottom surface of the piezoresistor  12 B. A top substrate  10 T is configured on a top side of the top electrode  11 T; and a bottom substrate  10 B is configured on a bottom side of the bottom electrode  11 B. 
       FIG. 10B  shows an interface between the top electrode and the piezoresistor 
     Since a top surface of the piezoresistor  12 B is rugged in a microscopic view so that partial area contacts exist to maintain an infinite resistance between the top electrode  11 T and the piezoresistor  12 B. 
       FIG. 11  shows an operation of the third embodiment 
       FIG. 11  shows that a current I passes through the top electrode  11 T, the piezoresistor  12 B and the bottom electrode  11 B when a pressure is applied against the pressure sensor, where I&gt;0. 
       FIGS. 12A ˜ 12 B show a fourth embodiment according to the present invention 
       FIG. 12A  shows that an instant response pressure sensor has a piezoresistor  12 T; a first electrode  11 LB, and a second electrode  11 RB coplanar with the first electrode  11 LB, are configured under a bottom side of the piezoresistor  12 T; wherein the piezoresistor  12 T contacts the top surface of the two electrodes  11 LB,  11 RB with an infinite resistance therebetween before a pressure applied against the pressure sensor, where I=0; a top substrate  10 T is configured on a top side of the piezoresistor  12 T; and a bottom substrate  10 B is configured on a bottom side of the two electrodes  11 LB,  11 RB. 
       FIG. 12B  shows an interface between the piezoresistor and the two electrodes 
     Since a bottom surface of the piezoresistor  12 T is rugged in a microscopic view so that partial area contacts exist to maintain an infinite resistance between it and the two bottom electrodes  11 LB,  11 RB. 
       FIG. 13  shows an operation of the fourth embodiment 
       FIG. 13  shows that a current I passes through the left electrode  11 LB, the piezoresistor  12 T and the right electrode  11 RB when a pressure is applied against the pressure sensor, where I&gt;0. 
       FIGS. 14A ˜ 14 B show a fifth embodiment according to the present invention 
       FIG. 14A  shows that an instant response pressure sensor has a first electrode  11 LT, and a second electrode  11 RT coplanar with the first electrode  11 LT; a piezoresistor  12 B is configured under a bottom side of the two electrodes  11 LT,  11 RT; wherein the electrodes contact the top surface of the piezoresistor  12 B with an infinite resistance therebetween before a pressure applied against the pressure sensor, where I=0. A top substrate  10 T is configured on a top side of the two electrodes  11 LT,  11 RT; and a bottom substrate  10 B is configured on a bottom side of the piezoresistor  12 B. 
       FIG. 14B  shows an interface between the two electrodes and the piezoresistor 
     Since a top surface of the piezoresistor  12 B is rugged in a microscopic view so that partial area contacts exist to maintain an infinite resistance between the piezoresistor  12 B and the two electrodes  11 LT,  11 RT. 
       FIG. 15  shows an operation of the fifth embodiment 
       FIG. 15  shows that a current I passes through the left electrode  11 LT, the piezoresistor  12 B and the right electrode  11 RT when a pressure is applied against the pressure sensor, where I&gt;0. 
       FIG. 16  shows a first application of the pressure sensor according to the present invention 
     An electronic pen  60  has an instant response pressure sensor  61  of the present invention configured on a backside of a tip base  62 . The tip base  62  is configured on a back side of a pen tip  61 . The instant response pressure sensor  61  is configured for sensing a pressure applied against the pen tip  61 ; an electrical signal is generated corresponding to the pressure applied for a further processing. A circuit board  64  is configured on a backside of the instant response pressure sensor  63 , for processing the signal received from the instant response pressure sensor  63 . The circuit board  64  electrically couples to a control circuit  66 , the control circuit  66  electrically couples to a computer  67  which in turn electrically couples to a display  68 . A sensing panel  65  is configured for sensing the pressure applied from the pen tip  61 . The sensing panel  65  electrically couples to the computer  67 , so that the display  68  can display an image delineated by the pen  60 . 
       FIG. 17  shows a second application of the pressure sensor according to the present invention 
       FIG. 17  shows that a mobile phone  70  has a volume control button  71 ; the volume control button  71  has top end  711  depressible to increase the volume, and has a bottom end  712  depressible to decrease the volume. A first instant response pressure sensor  72  is configured on a bottom side of a top end  711  of the button  71  for sensing pressures applied against the top end  711  of the button  71 . A second instant response pressure sensor  73  is configured on a bottom side of the bottom end  712  of the button  71  for sensing pressures applied against the bottom end  712  of the button  71 . A first electrical signal is generated corresponding to the pressure applied against the top end  711  of the button  71  for a further processing, and a second electrical signal is generated corresponding to the pressure applied against the bottom end  712  of the button for a further processing. 
     While several embodiments have been described by way of example, it will be apparent to those skilled in the art that various modifications may be configured without departs from the spirit of the present invention. Such modifications are all within the scope of the present invention, as defined by the appended claims.