Saint-Gobain CHR K102, consisting of a polyimide film backing and a high-tack acrylic pressure-sensitive adhesive, is used on powder-coat and e-coat lines for masking machined bearing journals, threaded bores, grounding bosses, and stainless steel alignment pins that must remain free of cured polyester, epoxy, or polyurethane powders. In a typical powder-coat cell, the masked part passes through an alkaline immersion wash, a dry-off zone at 120–150°C, a corona spray booth, and a cure oven held at 180–205°C for 10–25 min depending on the coating formulation. The polyimide backing does not shrink or embrittle under these cure conditions; the acrylic adhesive is selected instead of a silicone system when the subsequent assembly step is bonding, welding, or painting because acrylic adhesive residues are more readily removed by solvent wipe and do not poison downstream adhesion. Tape application on production lines is normally performed with a hand squeegee or pneumatic lamination roller at 2–4 bar. The tape edge must be burnished to prevent powder from being driven under the mask by electrostatic wrap-around. Clean removal is achieved when the part is cooled below 60°C and the tape is pulled back at 135–180° to itself. Bake cycles above 220°C or soak times beyond 30 min can shift the acrylic adhesive from cohesive failure to adhesive transfer, leaving a visible deposit on zinc-phosphated steel and aluminum. Published data for K102-specific peel adhesion after extended powder-cure cycling is limited; therefore, production qualification on the actual substrate and pretreatment is performed using ASTM D3330/D3330M 180° peel and ASTM D3652 thickness measurement before line release.

How Is an Acrylic PSA Polyimide Tape Qualified Against Wave-Solder Flux Ingression?

In PCB assembly, gold-finger edge connectors are masked before wave soldering to prevent flux, solder balls, and hot air from wetting or contaminating the contact area. K102 is applied over the edge connector and pressed down with a rubber lamination roll at 3–5 bar; air entrapment at the board edge must be avoided because flux can wick through open channels. During wave solder, the tape sees preheat temperatures of 90–110°C, a molten SnAgCu or legacy SnPb wave at 250–265°C, and momentary contact times of 3–6 s. The polyimide backing remains dimensionally stable under this short thermal excursion, but the acrylic adhesive is the limiting layer: prolonged contact above 260°C or repeated wave passes can plasticize the adhesive and cause oozing at the board edge, which can transfer to the gold contact. Qualification testing typically includes tape peel after the thermal profile, ionic contamination testing per IPC-TM-650 method 2.3.25, and optical inspection of the gold fingers at 10–20× magnification. Unlike silicone PSAs, acrylic adhesive does not leave low-surface-energy siloxane films that impair wire bonding or connector solderability. The tape is removed after the board has cooled to 40–60°C; pulling at a 90–180° angle reduces adhesive splitting. For applications requiring repeated wave solder cycles, published K102-specific cyclic thermal resistance data is limited, so users characterise the adhesive with ASTM D3654 shear adhesion failure temperature and ASTM D3330/D3330M peel on ENIG and gold-plated substrates before setting process limits.

Lithium-ion battery pack assembly deploys K102-type polyimide/acrylic tape as a secondary insulation barrier on cell tabs, welded nickel-copper interconnect regions, and voltage sense leads. The polyimide film provides dielectric isolation; the acrylic PSA bonds to aluminum, copper, nickel, and PET/polyimide films commonly present in prismatic and pouch cell modules. The adhesive must withstand module compression and vibration testing without edge lifting or slitting. Dielectric verification is normally performed at 500 V DC for 1 min using a hipot tester, with a leakage current limit below 0.1 mA. In practice, the acrylic adhesive should not be specified for regions immersed in carbonate-based liquid electrolyte, because ester and carbonate components can swell the PSA and reduce shear holding power; this is a known limitation for acrylic adhesive tapes in battery service. The tape is better suited to dry exterior surfaces, bracket insulation, and busbar isolation outside the electrolyte environment. Testing on production lines commonly follows IEC 60664-1 creepage and clearance guidelines, with dielectric strength evaluated on the taped assembly rather than on the film alone. Because battery busbar temperatures can reach 85–100°C during fast charge, the acrylic adhesive must be checked for edge lifting after thermal cycling. A suitable screening method is thermal shock per IEC 60068-2-14 test Na between −40°C and 105°C for 100 cycles. The tape edge must be die-cut without exposed adhesive filaments; laser cutting can create carbonised edges that reduce dielectric strength and require post-process inspection.

Electrical Clearance and Creepage Enhancement in High-Voltage Busbar Wrapping

For IGBT stacks, DC-link capacitors, and inverter busbar assemblies, K102 is wrapped over copper busbars with tight radius bends to increase insulation between phase conductors. The polyimide backing has high dielectric strength; general polyimide film literature reports 200–280 kV/mm at 25 µm, but converted tape values are lower due to adhesive coverage, voids, and electrode configuration. Process windows for busbar wrapping require the tape to be applied with 50% overlap in a half-lap pattern, followed by a silicone-free roller or rounded scraper to consolidate the adhesive. Air pockets are unacceptable because partial discharge inception voltage drops sharply at voids under 800–1,000 V DC bus conditions. End users typically test the wrapped busbar using ASTM D149 short-time dielectric breakdown of the tape stack. Electrical tape properties are screened per ASTM D1000 for dielectric breakdown, adhesion, and corrosion. Because the acrylic adhesive is an organic dielectric, the thermal class of the complete tape is lower than the polyimide film alone; continuous operation above 130°C can soften the adhesive and produce creep paths. In inverter busbar applications, the component surface is often plasma-cleaned or solvent-wiped with isopropanol before tape application to achieve peel adhesion above 4 N/cm on copper. Lifted edges at busbar bends are a documented failure mode when the tape is applied below 15°C, because acrylic PSA storage and application temperature limits usually require 20–35°C for optimal wet-out. Qualification to UL 510 and the applicable polyimide film sheet of the IEC 60454-3 series is often referenced, though product-specific K102 files should be confirmed against the manufacturer’s current certifications.

Transformer manufacturers apply K102-type polyimide/acrylic PSA tape between foil windings and over lead-out points where sheet-wound coils enter vacuum-pressure impregnation. The tape must hold under winding tension while the coil is built, then survive varnish impregnation and oven cure at 130–150°C without lifting or contaminating the varnish bath. Winding operators adjust tape tension to 5–15 N per cm width to avoid tearing the film or creating wrinkles. Acrylic PSAs are selected over rubber-based adhesives in this application for their compatibility with polyester and epoxy varnishes commonly used in Class F and Class H dry-type transformers, but solvent-borne varnishes containing strong ketones or aromatics can attack the adhesive over long immersion times. On finished coils, the tape interface is inspected for voids and wrinkles before varnish. In high-voltage load tests, assembled transformers are assessed for partial discharge per IEC 60270; the tape interface can be a source of partial discharge if air gaps are present. The acrylic adhesive bond must withstand thermal aging inside the insulation system, but the tape alone does not carry a thermal class rating. Transformer insulation systems are qualified as complete systems per UL 1446, so tape selection should be validated inside the final insulation system rather than by film temperature index alone. Acrylic PSA can be more prone to edge lifting due to varnish cure shrinkage than silicone PSA at Class H temperatures above 180°C. Published data for K102-specific thermal endurance in transformer varnish systems is limited.

When Silicone Contamination Cannot Be Tolerated in a Paint Shop

In automotive refinishing and aerospace spray-booth operations, K102 is used to mask connector bodies, sensor mounting seats, wheel-speed rings, and fuel filler recesses before electrocoat, primer, basecoat, and clearcoat. The acrylic PSA is deliberately chosen because it is a silicone-free adhesive system, unlike conventionally specified silicone polyimide tapes that can transfer siloxane traces to masked surfaces. Silicone contamination causes cratering and fish-eye defects in urethane clearcoats; paint shop audits commonly inspect tape residues using X-ray photoelectron spectroscopy (XPS) or FTIR with a silicon detection threshold below 0.1 atomic %. The tape must remain in position through bake cycles up to 150°C for waterborne basecoat and 120–140°C for clearcoat curing, and then remove cleanly without adhesive residue on aluminum, galvanized steel, or e-coat. Removal after bake is performed at 20–50°C; hot tape removal can tear the film and leave adhesive split. On textured castings, the acrylic adhesive needs higher pressure during application to flow into surface roughness and prevent paint bleeding. For sharp radii and embossed engine blocks, a polyimide backing with a dry film thickness of 25–50 µm is typically used; conformability at the edge is improved by application with a soft rubber roller rather than a hard plastic scraper. Paint process qualification for tape masking includes adhesion testing of subsequent paint layers per ISO 2409 cross-cut and ASTM D3359 tape adhesion. Published data for K102-specific clean-removal performance after multiple bake cycles is limited; production painters therefore qualify the tape on each coating system and substrate combination before line introduction.