The polydimethylsiloxane (PDMS) on the chip can’t be removed at all. Which type of cleaning agent should be used?
Polydimethylsiloxane (PDMS) is a siloxane polymer with high chemical stability, which is difficult to remove by conventional cleaning. It is necessary to select targeted cleaning agents based on its hydrophobicity and chemical inertness, while strictly avoiding damage to the chip (silicon substrate, metal wiring, coating, etc.). Specific suggestions are as follows:
This type of cleaning agent is specially designed to remove siloxane-based polymers (such as PDMS and silicone rubber residues). It usually contains non-polar solvents (e.g., alkanes, aromatics) and a small amount of co-solvents, which can effectively swell or dissolve PDMS and have good compatibility with silicon and metals (common chip wiring materials like aluminum and copper).
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Examples: 3M’s silicone rubber remover, Henkel’s silicone residue cleaner, etc. (It is necessary to confirm that the product description clearly states it is suitable for electronic component cleaning).
If no specialized cleaning agent is available, you can try non-polar organic solvents with strong solubility for PDMS. However, it is mandatory to conduct a small-scale test on the non-critical area of the chip first to confirm there is no corrosion or oxidation before full-scale cleaning:
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Toluene or Xylene
They have strong non-polarity and a certain swelling and dissolving effect on PDMS, making them suitable for removing thick PDMS residues. Operation must be carried out in a fume hood (highly volatile and flammable), and contact with metal wiring should be avoided (long-term immersion may slightly corrode some metals, so it is recommended to shorten the soaking time).
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Cyclohexane or n-Hexane
With lower polarity, they have a mild swelling effect on PDMS and low corrosion to metal and silicon substrates, making them suitable for precision chip cleaning. Ultrasonic cleaning can be used in combination (power ≤ 50W, time 5-10 minutes) to enhance the cleaning effect.
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Dichloromethane (Use with Extreme Caution)
It has strong solubility for PDMS but may damage the photoresist and organic coatings on the chip surface. It is only recommended for uncoated bare silicon chips, and the time must be strictly controlled (≤ 5 minutes).
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Compatibility Testing: First, soak the edge or non-functional area of the chip with a small amount of cleaning agent, observe whether phenomena such as metal discoloration, silicon wafer whitening, or coating peeling occur, and confirm safety before full-scale cleaning.
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Ultrasonic Assistance: For stubborn residues, low-power ultrasonic cleaning (30-50W) can be performed in organic solvents. Ultrasonic vibration is used to accelerate PDMS detachment, but the time should not be too long (to avoid damage to the chip structure).
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Subsequent Rinsing: Thoroughly rinse the residual organic solvents with anhydrous ethanol or isopropyl alcohol, and finally dry the chip via nitrogen blow-drying or low-temperature drying in an oven (≤ 60℃ to prevent thermal damage to the chip).
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Safety Protection: Most organic solvents are flammable and volatile. Operations must be conducted in a fume hood; gloves and goggles should be worn, and the solvents should be kept away from ignition sources.
If the chip contains sensitive components (such as sensors and precision circuits), it is recommended to prioritize electronic-grade specialized silicone removers (e.g., siloxane cleaning agents commonly used in the semiconductor industry) or consult the chip manufacturer for recommended compatible cleaning agents. This avoids chip function failure caused by improper solvent selection.
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