Fused Silica vs Borofloat Glass: How to Choose: custom precision glass machined to drawing with inspection reports. Single-piece prototypes to production volumes, quoted from your drawing.
Engineers rarely need a winner in fused silica vs borofloat glass: how to choose – they need the boundary. It runs along thermal expansion versus price: fused silica when CTE or UV matters; Borofloat for bonded MEMS at a third of the cost.
Side by side
| Fused Silica | Borofloat 33 | |
|---|---|---|
| CTE | 0.55 x 10^-6 /K | 3.25 x 10^-6 /K |
| Service temp | 1,100 C continuous | 450 C continuous |
| Transmission | 185 nm – 2.5 um | 350 nm – 2.0 um |
| Hardness | 500 kg/mm2 | 480 kg/mm2 |
| Density | 2.20 g/cm3 | 2.23 g/cm3 |
| Signature trait | near-zero thermal expansion | float-glass flatness off the line |
The decision axis is thermal expansion versus price. Fused silica when CTE or UV matters; Borofloat for bonded MEMS at a third of the cost.
DFM notes from the shop floor
Before sending the RFQ, check these against your drawing:
- Over-specification is the quiet budget killer: a 20/10 scratch-dig face costs roughly three times an 80/50 face, so grade each surface individually.
The full rules live in our tolerance design guide and holes and edges design guide.
Who orders this
Orders for fused silica vs borofloat glass: how to choose cluster in scientific instruments (reference flats, cells, prism mounts, stage inserts); medical diagnostics (flow cells, slides, microplate bottoms, cuvette windows); mems devices (cap wafers, TGV substrates, motion-sensor lids).
If the part is easier to draw than describe, the custom glass machining 3D + 2D builder turns dimensions into an RFQ in a few minutes.
For adjacent specifications, see custom FTO glass, precision glass drilling, optical glass options.
Buyer questions, answered
How fast can prototypes ship?
Machined prototypes ship in 5 – 10 working days. Coated or bonded parts add 1 – 2 weeks depending on queue slots.
What files do you need for a quote?
A dimensioned PDF plus DXF or STEP geometry. If only a sketch exists, our drawing review service formalizes it before quoting.
Do parts ship with inspection data?
Dimensional reports, surface certificates and material certs per melt are available; specify the level on the RFQ.
Which should I choose?
As a rule: fused silica when CTE or UV matters; Borofloat for bonded MEMS at a third of the cost. Borderline cases are worth a materials review with our engineers.
Specifications on this page were last reviewed by our engineering team in August 2026.