Core Performance Indicators to Consider When Applying PTFE High-Temperature Tape in Vacuum Coating, Vacuum Heat Treatment and Other Vacuum Environments

Jiangsu Aokai New Materials, a professional manufacturer of PTFE high-temperature tape, shares professional guidance. When used in vacuum coating, vacuum heat treatment and other vacuum environments, PTFE high-temperature tape has vastly different core performance requirements compared with atmospheric applications. Low outgassing, low volatile emission and high cleanliness are the top priorities. The key indicators to be evaluated are listed as follows:

1. Vacuum Outgassing Property (Most Critical Indicator)

This is the decisive performance index for vacuum applications. Under low pressure and high temperature, the tape will release volatile gas, which degrades vacuum degree. Condensed volatiles contaminate optical components, sputtering targets and workpieces, resulting in foggy coatings, poor film adhesion and even complete product rejection.

· Total Mass Loss (TML): General requirement TML ≤ 1.0%; high-standard applications such as aerospace and optical industries demand TML ≤ 0.5%.

· Collected Volatile Condensable Materials (CVCM): Strictly controlled, normally CVCM ≤ 0.1%; ultra-rigid scenarios require CVCM ≤ 0.01%.

2. Temperature Resistance Grade

· Continuous service temperature: The PTFE-coated fiberglass substrate of PTFE tape can withstand long-term exposure at 260°C. However, the temperature resistance of the adhesive layer must be verified simultaneously. Conventional silicone PSA offers continuous heat resistance around 200°C, while high-performance silicone adhesive can reach 260°C.

· Short-term peak temperature: Check whether instantaneous peak temperatures during processing exceed the tape’s short-term thermal limit (generally ≤300°C). Excess temperature will carbonize and decompose the adhesive layer, causing severe contamination inside the vacuum chamber. Note: If vacuum heat treatment temperature far exceeds 260°C, PTFE tape is no longer applicable; polyimide (Kapton) tape or aluminum foil tape shall be adopted instead.

3. Adhesive Type & High-Temperature Holding Power

· Adhesive system selection: Silicone pressure-sensitive adhesive is the mainstream choice for vacuum applications due to its superior heat resistance. Nevertheless, ordinary silicone adhesives contain abundant low-molecular siloxanes, which volatilize under high-temperature vacuum and contaminate workpieces, especially optical surfaces and electrical contact areas. Therefore, specially purified low-outgassing silicone adhesive or non-silicone adhesive formulations are required.

· High-temperature holding power: Under combined vacuum and high-temperature conditions, creep, edge lifting or full peeling of the tape will directly block vacuum pipelines and introduce new contamination sources. The shear holding duration at operating temperature must be validated.

4. Cleanliness & Ionic Contamination

· Cleanroom compatibility: The tape shall be free of fiber shedding and lint at cutting edges. Tapes manufactured in cleanroom facilities are preferred.

· Low ionic content: For vacuum processes in semiconductor and MEMS industries, halogen ions (Cl) and metal ions (Na, K) contained in the tape will precipitate at high temperature, corroding circuits or altering doping concentration. Request ionic extractables test reports from suppliers.

· Zero silicone oil migration: Apart from condensable volatiles, free silicone oil inside adhesives may creep across surfaces and cause failure in subsequent bonding and welding processes. Specify zero silicone oil migration grade for critical applications.

5. Surface Anti-Static Performance

PTFE is inherently a high-insulation material. Static charge easily accumulates on its surface through friction or peeling inside vacuum chambers. Electrostatic discharge may damage sensitive electronic components or attract particulate pollutants.

· Indicator requirement: For shielding and protection of electrostatic-sensitive zones, anti-static PTFE tape is required with surface resistivity ranging from 10⁶ ~ 10⁹ Ω/sq, and stable anti-static performance must be maintained after high-temperature exposure.

6. Plasma & Chemical Resistance

· Plasma resistance: In sputtering and PECVD processes, tape exposed to plasma atmosphere will be etched, releasing fluorine free radicals that pollute deposited films and erode vacuum chambers. Evaluate applicability in advance, or switch to more plasma-resistant polyimide tape if necessary.

· Chemical resistance: Residual oil vapor and cleaning solvents may exist during vacuum heat treatment; both adhesive and substrate shall resist swelling and chemical reactions.

7. Dimensional Stability & Thermal Shrinkage Rate

Excessive thermal shrinkage at high temperature will expose masked edges or generate adhesive wrinkles, impairing masking precision and conformability.

· Indicator requirement: Review thermal shrinkage data provided by manufacturers (tested after 30 minutes at 260°C). Premium vacuum-grade tape achieves shrinkage below 2% or even lower.

Summary of Selection Recommendations

When purchasing PTFE high-temperature tape for vacuum environments, heat resistance alone is insufficient. Request ASTM E595 outgassing test reports from suppliers, clearly state vacuum service conditions and demand specialized low-outgassing tapes with purified silicone adhesive. For critical production processes, conduct small-scale coupon testing to measure partial pressure fluctuations on vacuum gauges and assess potential contamination to finished products.

The above technical content is provided by Jiangsu Aokai New Materials Technology Co., Ltd.

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