🔥 Anodic Bonding Kit
4" (100mm) BF33 + Silicon Pair
1x 100mm BF33 (500µm DSP)
1x 100mm Silicon (500µm SSP)
Matched CTE for perfect hermetic seals.
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Key Properties (at 20°C)
- CTE: 3.25 x 10⁻⁶ K⁻¹
- Density: 2.23 g/cm³
- Refractive Index: 1.4714 (at 587nm)
- Transformation Temp: 525°C
In-Stock Borofloat 33 Inventory
We stock standard thicknesses optimized for anodic bonding and microfluidics.
| Diameter | Thickness | Polish | Surface Quality | Application | Link |
|---|---|---|---|---|---|
| 100mm (4") | 500µm ± 25µm | DSP | 60/40 | MEMS Bonding | Buy |
| 100mm (4") | 700µm ± 25µm | DSP | 60/40 | Microfluidics | Buy |
| 100mm (4") | 1.1mm ± 0.1mm | DSP | 60/40 | Thick Substrate | Buy |
| 150mm (6") | 500µm ± 25µm | DSP | 60/40 | MEMS Bonding | Buy |
| 200mm (8") | 725µm ± 25µm | DSP | 60/40 | Wafer Bonding | Buy |
Why Borofloat 33 for Anodic Bonding?
Anodic bonding creates a permanent, hermetic seal between glass and silicon without adhesives. It requires the glass to have sodium ions (Na+) and a Coefficient of Thermal Expansion (CTE) closely matched to silicon.
The "Silicon Match"
Silicon has a CTE of ~2.6 ppm/K. Borofloat 33 has a CTE of 3.25 ppm/K. This close match ensures that when the bonded stack cools down from the bonding temperature (typically 300-400°C), minimal residual stress is generated, preventing the wafer from bowing or cracking.
Borofloat 33 vs. Pyrex 7740
Customers often ask: "Can I use Pyrex instead?" Here is the comparison:
| Feature | SCHOTT Borofloat 33 | Corning Pyrex 7740 |
|---|---|---|
| Manufacturing | Microfloat Process (Float Glass) | Rolled Process |
| Surface Quality | Superior Flatness (Fire Polished) | Wavier (Often requires polishing) |
| Anodic Bonding | Excellent (Industry Standard) | Good (Legacy Standard) |
| Availability | High (Widely Stocked) | Lower (Pyrex 7740 is discontinued) |
Note: Pyrex 7740 sheet glass was discontinued by Corning. Borofloat 33 is the direct functional replacement and offers superior surface flatness due to the float manufacturing process.
Microfluidics Applications
Borofloat 33 is ideal for microfluidic chips due to its excellent optical transparency and chemical inertness. It can be:
- Wet Etched: Using HF (Hydrofluoric Acid) to create channels.
- Laser Machined: For drilling inlet/outlet holes.
- Thermally Bonded: Fused to another glass wafer to seal channels.
Need Thinned Glass?
We can thin Borofloat 33 wafers down to 100µm (0.1mm) or less for flexible electronics and sensor applications. Contact us for custom thinning services.
🔬 Application Spotlight: Microfluidic Imaging
The Challenge: A research lab needed to fabricate a Silicon-Glass device with etched microchannels. They required a glass cap thinner than 170µm to allow for high-resolution microscopy through the sealed device.
The Solution: Standard wafers are too thick for high-mag objectives. We supplied 100mm Borofloat 33 wafers thinned to 175µm with a Double Side Polish (DSP). This provided:
- Optical Clarity: Thin enough for short working distance objectives.
- Hermetic Seal: Perfect CTE match for anodic bonding to the 500µm Silicon channels.
- Surface Quality: 60/40 Scratch/Dig to prevent scattering.