Sapphire thinning technology solution

Featured Process Scheme: Sapphire Substrate

Faced with sapphire substrates with a Mohs hardness of 9.0 and low fracture toughness, a systematic experiment was conducted in four dimensions: grinding wheel screening, biaxial speed matching, wafer table type, and spindle power to lock in a stable and reproducible thinning process window.

Material4-inch sapphire substrate
Using equipment:AG7500
TTV stability:2 μm

Material Properties

Sapphire (Al ₂ O ∝) is a single crystal material with a hardness second only to diamond, with a Mohs hardness of up to 9.0 and extremely high surface wear resistance; However, its fracture toughness is relatively low and it belongs to a typical brittle material. In precision thinning processing, it is necessary to strictly control the processing stress to avoid microcracks or edge collapse.

4-inch sapphire substrate is the mainstream choice in the current market: compared to 2-inch area, it increases by about 4 times, reduces costs by more than 30%, and maintains a stable yield of 82-85%, which is the balance point between technological maturity and market demand.

• Mohs hardness:9.0 (second only to diamond)

• Vickers hardness:1700–2000 kgf/mm²

• Bending strength:About 400 MPa

• Fracture toughness:1.5–2.0 MPa·m^1/2

Core market applications

4-inch sapphire substrates are widely used in high-end technology fields.

Mini/Micro LED · Consumer Electronics and Display

Graphics sapphire substrate (PSS) can increase light extraction efficiency by 15% -30%, perfectly adapting to high-density, high brightness high-end display technologies such as Mini/Micro LED.

RF and Power Electronics · Industry and Communication

The ideal substrate for SOS integrated circuits, GaN power devices, and RFID RF chips, meeting high-end application needs such as 5G/6G communication, new energy vehicles, and photovoltaic inverters, with a compound annual growth rate of over 12% in the market.

Optical Windows and Protection · Consumer Electronics and Military Industry

With extremely high hardness and wear resistance, it is widely used in protective lenses for mobile phone cameras, high-end watch mirrors, industrial optical windows, and aerospace precision instruments.

Process Optimization Experiment

Four dimensional systematic experiments to determine the optimal process window.

Experiment 1 | Grinding Wheel Screening Experiment

Test different types of grinding wheels such as 6A2T-M-D46, SD300, and 6A2-D320 # - M75, with a focus on verifying the changes in material removal rate, wear ratio, and wafer TTV.

Conclusion: The 6A2-D320 # - M75 grinding wheel has the lowest wear ratio under good TTV conditions.

Experiment 2 | Dual axis speed matching experiment

Explore the speed coupling relationship between the spindle (2500-1750rpm) and the bearing platform (60-190rpm), and analyze the machining stability and material removal uniformity under different speed ratios.

Conclusion: The optimal ratio of spindle 1750rpm and bearing plate 190rpm is obtained.

Experiment 3 | Optimization Experiment of Bearing Platform Type

Compare different tabletop support profiles (0,0, -18/0, -1, -22/0, -3, -28, etc.) and quantitatively analyze their impact on wear and TTV.

Conclusion: After optimizing the table surface shape, the precision of thinning the wafer meets the requirements of packaging level applications.

Experiment 4 | Spindle Power Configuration Experiment

Evaluate two power schemes of 7.5kW and 12kW, balancing material removal efficiency per unit time and equipment energy consumption cost while ensuring grinding quality.

Conclusion: The 12kW scheme has a better wear ratio and provides data support for capacity planning.

Experimental results data

15 sets of experimental verification, the process is stable and reproducible.

• TTV control 2 μ m:All 15 experimental TTVs remained stable at 2 μ m, demonstrating extremely high control over thickness uniformity.

• Surface roughness Ra 0.15-0.25 μ m:The surface roughness remains stable within this range, meeting the subsequent process requirements.

• Grinding wheel wear ratio 1:4.5~1:9:The wear ratio fluctuates within this range, and under specific conditions, the lifespan of the grinding wheel is longer and the cost is better.