These products feature thermal expansion characteristics which are extremely close to that demonstrated by silicon within a wide range of temperatures. They can be firmly bonded to silicon substrates (basal plates) through anodic bonding. As such, these products are used for support glass and wafer level packages of MEMS sensors.

Main Applications

  • Wafer level packages for MEMS substrates (basal plates)
  • Pressure sensors and acceleration sensors

Features

  • MEMS elements feature very fine and fragile structures, the type of which experience movement due to static electricity. As such, wafer level packages are often used to bond and seal together glass and silicon prior to the dicing process using a bonding method called “anodic bonding.”
  • • Sensors featuring structures such as this detect, with a high degree of sensitivity, changes in pressure and acceleration which result from the distortion seen in the microstructures of silicon. If a difference exists in terms of the thermal expansion coefficients of the silicon and glass, the output voltage ends up fluctuating in contrast with the distortion experienced by the silicon. This may affect the precision of the sensors.
  • While borosilicate glass has traditionally been used for anodic bonding, we provide a series of products called the SW Series, which further conforms with the thermal expansion characteristics of silicon single crystals. There are currently three types of glass products in the SW Series: SW-3, SW-Y and SW-YY. The SW-YY product features great thermal expansion characteristics and also allows anodic bonding to take place at temperatures which are 50 to 100 degrees (Celsius) lower than that experienced during instances where conventional borosilicate glass is used.

Table: Glass Wafer Characteristics

  Unit SW-3 SW-Y SW-YY Borosilicate glass Thermal characteristics
Thermal expansion coefficient ×10-7/°C 36 33 33 33 30 to 300°C
Strain point 615 630 590 510 Japanese Industrial Standards (JIS)
Annealing point 660 675 640 560 Japanese Industrial Standards (JIS)
Softening point 890 895 850 820 Japanese Industrial Standards (JIS)
Mechanical characteristics
Specific gravity   2.54 2.52 2.46 2.23  
Young's modulus GPa 80 78 82 64 Resonance method
Rigidity GPa 34 33 34 27 Resonance method
Poisson's ratio   0.19 0.18 0.2 0.2 Resonance method
Vickers hardness GPa 6.1 6.1 6.1 6.1  
Optical characteristics
Refractive rate   1.520 1.519 1.518 1.474 nd(589.3nm)
Electrical characteristics
Volume resistivity Ω・cm 10.6 10.7 10.3 11.4 100℃
    8.3 8.3 7.8 9.4 200℃
Dielectric constant   6.1 6.0 6.3 4.6 Room temperature (1 MHz)
Dielectric dissipation factor   0.01 0.01 0.01 0.01 Room temperature (1 MHz)
Chemical characteristics
Acid resistance mg/cm2 0.30 0.16 0.09 0.01 Immersion in 1/100N HNO3 at 95℃ for 20 hours
Alkali resistance mg/cm2 0.09 0.17 0.16 0.14 Immersion in 5% NaOH 80℃ for 1 hour
            80°C for 1 hour
Water resistance mg/cm2 0.05 0.07 0.05 0.04 Immersion in pure water at 95℃ for 40 hours
Other
Alkali component   Na20 Na20 Li20 Na20  
Features   General product Low-expansion product Low expansion product, low-temperature bonding    

Thermal Expansion Characteristics (Comparison with Silicon and Other Types of Glass)

Thermal Expansion Characteristics (Comparison with Silicon and Other Types of Glass)

Difference in Thermal Expansion Coefficient Compared to Silicon

Difference in Thermal Expansion Coefficient Compared to Silicon

Machining Examples

Metal (gold, chromium, titanium, etc.) coating on substrates (basal plates), ultrasonic machining and sand blasting, as well as hole completion performed via etching, spot facing, and other types of machining

(mm) Example of hole completion after hole machining t= 0.4-0.2 tapered hole(mm) Example of hole completion after hole machining t= 0.4-0.2 tapered hole
t = 1 to 3 (mm) Holes resulting from hole completion performed via ultrasonic machining Up to 1000 pcs per area around 6 inches in sizet = 1 to 3 (mm) Holes resulting from hole completion performed via ultrasonic machining Up to 1000 pcs per area around 6 inches in size
t=0.5(mm) Spot facing (3 x 2 x h 0.2) + Hole completion (4 x 1 hole)t=0.5(mm) Spot facing (3 x 2 x h 0.2) + Hole completion (4 x 1 hole)