Polyimide Tape vs PET vs Crepe Masking: Which Heat Window Do You Need?

Technical guidesPublished 07 November 2026Updated 07 November 2026

Polyimide tape, high-temperature PET film tape and crepe-paper heat-resistant masking tape all claim a warm process, and the one that fits your line is decided by three inputs: the peak and dwell the part actually sees, what the surface underneath is, and what residue would cost you downstream. Nobody needs a PI grade for a 60 °C hot-air dry, and a crepe tape will not survive a reflow profile no matter what the price per roll says.

What each construction is made of

The three families differ in the backing first and the adhesive second, and that order predicts how they behave on a bake-and-peel cycle.

Polyimide tape — a PI film with a silicone or acrylic coat — is the temperature reference of the group. The film does not soften at board-oven temperatures, so the load falls on the adhesive and at the edge of the strip, and the film stays dimensionally stable, which is why it masks defined features rather than only covering zones.

PET film tape with an acrylic or silicone coat has a higher softening point than PVC and general masking film, holds its shape and cuts cleanly. Its weak point is long exposure: the film discolors, stiffens and can shrink slightly, and a stiff film on a low-tack coat lifts at the edge instead of staying where it was placed.

Crepe paper with a rubber or synthetic coat is the economical option for paint bakes and warm drying. The paper conforms and takes a curve, which is why it is the default in refineries and sheet-metal work. Under an oven profile it does the opposite of what you want: it dries, darkens and breaks into fibres when peeled, and the fibres are the residue.

The comparison, route by route

Route	Where it fits	Its limits
Polyimide (PI) film tape	Reflow and wave masking, gold-finger and connector masking, coil insulation, solder-resist protection, board-level insulation in a pack	Highest cost per roll of the three; silicone coats can transfer onto surfaces later coated or wired; thin film is nick-sensitive
High-temperature PET film tape	Hot-air and warm bake work, short oven exposures below the PI band, wrapping where stiffness and a clean cut edge help	Discolors and stiffens on long exposure; edge lift on smooth surfaces; not the route for repeated passes
Heat-resistant crepe masking	Paint and coating bake-off, industrial masking below the electronics band, bundling and protection	Fibres and adhesive left after baking; poor behaviour once heat-soaked; low moisture resistance
Silicone boots, caps, liquid mask	Through-holes, connector bores, compound curves, large exclusion zones	Handling and storage of reusable parts; coverage control with liquid mask; neither stays in the assembly as an insulator

Process temperature bands for these families vary by supplier, grade and test method, and the figures quoted around the trade are indicative industry ranges, not our commitment. The governing number is the one declared on the TDS for the grade you order, read against your own profile.

Where the cost actually sits

Per roll, PI costs more than PET and PET costs more than crepe. Per masked site the ranking changes with the process, and four items move it: application time, whether the tape has to be cut to shape by hand, whether removal leaves something somebody then cleans, and what a lifted edge costs if it fails a test.

A cheap tape that shreds on removal turns one operator-minute of masking into three minutes of picking fibres off a board, and a wire-bond or coating step re-qualified because of siloxane transfer costs more than the reel that caused it. Conversely, specifying polyimide tape for an 80 °C drying tunnel buys nothing but a higher invoice. Price the site, not the roll.

When tape is the wrong answer

We would rather say this than sell the wrong reel. If the exclusion zone is a through-hole, a connector bore or a compound curved housing, a silicone boot or cap seals better and comes off cleaner than any film. If the masked area is large and irregular, a liquid mask applied to a defined pattern beats laying strips. If the tape must sit on fresh powder coat or a low-energy plastic that will later be bonded, both the residue question and the wetting question point away from a silicone-coated film. And if the site has to survive the process and stay in the assembly as an insulator, that is an engineered part, quoted as a die-cut part with a defined construction, liner and inspection report rather than a roll off the shelf.

If you already run a branded PI grade

We supply and convert tesa, 3M and Sekisui materials, with the authorization scope confirmed per enquiry, brand, market and product family. A cross-reference against a part number you use is a way of finding where to start testing, not a substitution approval. Two grades of the same colour and nominal thickness can differ in coat weight, liner and release, and those are what your line notices first. Our cross-reference page sets out how we handle such a request: the named grade supplied and converted here, or a candidate construction tested on your substrate against your profile, decided from the report. The functional tape range shows the stock families.

FAQ

Is a PET high-temperature film tape ever the right answer over PI?

Yes, when the exposure is a warm bake or hot-air step that stays inside the PET band, the masked area is a simple zone rather than a defined feature, and removal happens while the part is still warm enough for a clean peel. In that case the lower cost per roll is a real saving, not a false economy.

Can the same PI grade serve as masking and as permanent insulation?

Sometimes the film is the same and the specification is not, because a masking tape is judged on how it releases and a permanent insulator on how it keeps adhering, withstands voltage and behaves at its cut edge. Where a part must do both, we quote a converted construction with the inspection stated against your drawing.

Commercial and process terms on this page are the questions a converter has to answer, not a standing offer. Order quantities, lead times, tooling charges, sample terms, freight and payment structures are confirmed at quotation against your drawing, your material and your destination, and only figures already published elsewhere on this site are stated as commitments.