Page History

...

Materials and manufacturing technologies

Find more information what materials have been used in your sensor and how the sensor is manufactured. You could use the following questions as a starting point:

• Does it contain Silicon? Is the structure crystalline or polysilicon?
• What plastic materials are used and why?
• Are metals used? Which ones? Why?
• How about ceramics and glasses?
• Why some materials are more favorable than others in your sensor or application?
• How is the sensor manufactured?
• What are the typical manufacturing process steps?

Complement your sensor article with these information. Add a sub-chapter to your article and named it: Materials and manufacturing technologies.

The datasheet of the LIS3L02AL accelerometer gives very little information about the materials used for manufacturing the sensor as well as how it is manufactured since the information about these is proprietary. What is known publicly is that the suspended structures which are attached to the substrate in anchors are made of silicon. There is no information about the manufacturing process of the sensor from STMicroelectronics. Fortunately, some other manufactures are generous enough to give some information about the manufacturing process of their sensor. The following gives steps in manufacturing accelerometers from IMV corporation.

• Step 1 - Prescription: The main ingredients are lead, zirconium and titanium with 4-5 kinds of additives to have better caking properties by combustion and electric characteristics.
• Step 2 - Mixture: The prescribed ingredients are put into a pot with zirconium boulders and water. The ingredients are mixed and crushed in this pot.
• Step 3 - Drying: The slurry of ingredients is poured into vat and dried in a drying room. Then, it sets as a plate with cracks.
• Step 4 - Crushing into pieces: The set plate is put into a mortar and crushed. To make finer ingredients, it is grinded down to powder.
• Step 5 - Mixture: The grinded ingredients are put into a pot with zirconium boulders and water, and mixed and crushed again. Before proceeding to the next step, the binder (PVA series) for shaping is added as a thickener.
• Step 6 - Making powder of ingredients: The slurry of ingredients is sucked in a tube by using the roller pump. The slurry is then dropped on a heated, spinning plate. The dripped ingredients become powder and are collected during this procedure. The powder made the spray dryer is a fine powder with a consistent grade and good fluidity for shaping.
  
  Image Added
• Step 7 - Shaping: The ingredients are put into a cylinder, and pressed with 1000-3000kg/cm² of pressure.
  The ingredients are set as a round plate.
  
  Image Added
• Step 8 - Removing grease: The set ingredients are put into the chamber which is heated to 400-600℃. It is for removing the grease of added binder (PVA series).
  
  Image Added
• Step 9 - Hardening: The ingredients are stuffed into a case (a box made of alumina). It is calcinated at 1000-1300℃. The ceramics (crystal) is obtained from the ingredients.
  
  Image Added
• Step 10 - Grinding: The hardened ceramics are ground on both sides to the specified thickness.
  
  Image Added
• Step 11 - Silver painting: Silver paste is printed on the ground surface of the ceramic by a screen printing press.
  
  Image Added
• Step 12 - Silver hardening: Silver paste is printed on the ground surface of the ceramic by a screen printing press.
  
  Image Added
• Step 13 - Polarization:

  The ceramic is put into the silicon oil heated approx.200℃ and high voltage 1-2kV/mm is added between the electrodes.Then, the random polarities are arranged in field direction are arranged to be in the same field direction. Thea piezoelectricity becomes apparent.

  Image Added

• Step 14 - Checks: Polarized ceramics are checked. Check points include

  
  
  1. Coupling coefficient (machine-electricity conversion coefficient)
  2. Resonance frequency
  3. Electric capacity
  4. Insulation resistance
  5. Curie point temperature
  6. Specific gravity
     
     
• Step 15 - Processing: Ceramics are processed into the shape required for a sensor. These shapes are the compressed type, shear type, round plate type, and square plate.
  
  Image Added
• Step 16 - Plating: The ceramic for the shear type is plated by non-electrolytic nickel on the processed side (polarization axis and horizontal direction) after processing, and is changed the electrode.
• Step 17 - Construction: Piezoelectric ceramics, machine processing parts and connectors are composed and connected with wires to construct a piezoelectric sensor. 
• Step 18 - Checks: The constructed sensor is checked. Check points include
  
  
  1. Charge sensitivity
  2. Capacitance
  3. Insulation resistance
  4. Frequency characteristics
  5. Temperature characteristics  etc.
     
     

The whole manufacturing process is completed after checking is done. [12.]

Selection of an accelerometer

...