How to handle gaps in a granite base?

Please translate the following Chinese text into English:

Cracks in granite bases (platforms) for semiconductors / precision equipment. The core principle is: first stop the crack, then structural reinforcement, and finally precision repositioning and calibration; the use of ordinary marble glue / cement is strictly prohibited. Low-shrinkage, high-rigidity, anti-static specialized epoxy must be used, and the entire process must be operated in a constant-temperature, dust-free environment.

I. First, determine the crack type (to decide the solution)

Hairline cracks (<0.2mm): Surface micro-cracks, no misalignment, minimal impact on precision → Cleaning   penetrating epoxy sealing.

Open cracks (0.2–2mm): Have width, no obvious misalignment → Slotting and cleaning   rigid epoxy filling   grinding and polishing.

Structural cracks (>2mm / through-cracks / misalignment): Base cracking, flatness / perpendicularity out of tolerance → Professional disassembly   bonding   mechanical reinforcement   regrinding and calibration.

Joint cracks (at the interface of two blocks): Joint cracking, light leakage / dust seepage → Realignment   structural epoxy   joint grinding   flatness re-measurement.

II. Precision Base Standard Repair Process (Semiconductor Grade)

1. Machine shutdown protection and environmental control

Power off the equipment, remove upper components, and completely unload the base;

Environment: 22±0.5℃, humidity 40%–60%, dust-free ISO7, to avoid temperature-induced deformation.

2. Thorough cleaning of cracks (Critical! Otherwise, debonding will occur)

Dry cleaning: Brush dust with a soft brush → Deep blow with 0.4–0.6MPa compressed air, no residual particles;

Degreasing: Wipe the crack and the 20mm area on both sides with acetone / anhydrous ethanol, wipe dry with a dust-free cloth;

Drying: Air dry naturally for 30 min or blow dry with hot air (≤40℃), water content in the crack <5%.

3. Crack pretreatment (depending on width)

Hairline cracks: No slotting required, directly penetrate with epoxy;

0.2–2mm cracks: Use a diamond thin blade to cut a V-shaped slot (width 3–5mm, depth 3–5mm), chamfer the slot opening to increase the bonding area;

>2mm / through-cracks: Drill and tap holes (M6–M8) on both sides, reserve positions for stainless steel connecting plates for later mechanical reinforcement.

4. Select the right materials (Semiconductor specialized, ordinary glues strictly prohibited)

Table

Crack Type Recommended Material Key Indicators

Hairline / Micro-cracks Low-viscosity penetrating epoxy Viscosity <100cps, shrinkage <0.5%, anti-static 10⁶–10¹¹Ω

Open / Joint cracks Rigid structural epoxy (1:1 or 2:1) Compressive strength >80MPa, thermal expansion <4.5×10⁻⁶/℃, Shore D hardness >80

Structural cracks Structural epoxy   stainless steel connecting plates Epoxy strength >3000PSI, connecting plates 304/316L, rustproof and non-magnetic

❌ Prohibited: Marble glue (high shrinkage, brittle), silicone sealant (soft, affects precision), cement (expansion, corrosion).

5. Filling and Curing (Constant Temperature, Dust-Free)

Glue Mixing: Mix according to the ratio (e.g.,2:1), stir for ≥90s, bubble-free; a trace amount of black pigment can be added (to match Jinan Blue);

Glue Pouring:

-cracks: Slowly inject with a syringe until the crack is overflowing;

Grooved cracks: Press and fill with a scraper, slightly higher than the surface by 0.mm (to compensate for shrinkage), avoiding bubbles;

Curing: Cure at a constant temperature of 22°C for 24h to reach 80%, and 48h for full cure; vibration, pressure, and temperature fluctuations are strictly prohibited during this period.

6. Grinding, Polishing   Precision Reset (! Restore to Nanometer Level)

Rough Grinding: Diamond grinding discs (#120→#400→#800) grind layer by layer, flush with original plane;

Fine Grinding: #1500→#3000 grinding discs, flatness ≤2μm/m, Ra≤0.05m;

Calibration: Re-check flatness / perpendicularity with a laser interferometer, overall fine grinding if necessary;

Anti-static: Spray an anti-static coating on the, re-measure resistance to 10⁶–10¹¹Ω.

7. Reinforcement and Prevention (Mandatory for Structural Cracks)

Mechanical Reinforcement Lock stainless steel connecting plates   high-strength bolts on both sides of the crack to prevent secondary cracking;

Vibration Isolation Optimization: Check active / passive vibration isolators, adjust and pre-compression to reduce vibration stress;

Daily Control: Constant temperature 22±0.5°C, avoid rapid heating and cooling, regularly (every 36 months) re-check precision.

III. Common Pitfalls (Must Avoid)

Using marble glue / ordinary epoxy: High shrinkage, brittle, prone to secondary cracking, precision not guaranteed;

Incomplete cleaning: Oil / dust leads to debonding and rework;

Room temperature / low temperature curing: Insufficient strength, significant deformation, strictly prohibited for semiconductor grade;

Filling without grinding: Surface protrusions / depressions, flatness out of tolerance, equipment movement jamming.

IV. When Factory Return / Professional Treatment is Mandatory

Cracks penetrating the base, obvious misalignment (>0.1mm);

Flatness / perpendicularity exceeding 00 grade (>2μm/m), cannot be repaired on-site;

Base material is loose, weathered, or cracks continue to expand;

Lithography machine / high-end inspection equipment bases must be repaired by the original factory / precision workshop.