Not all Sheets for carrier tape are engineered for the same job. If you are sourcing materials for converting or procuring reels for production, use this checklist. If the spec sheet doesn't clearly answer these five points, you might be taking a risk with your supply chain.

1. The Camber Limit

Why it matters: A curved tape won't index properly.

The number to ask for: Camber should be ≤ 1mm per 250mm length.

Result: Prevents "walking" off the feeder sprocket.

2. Surface Resistivity (Humidity Dependent)

Why it matters: ESD damage is invisible. You need consistent discharge, not conductivity.

The number to ask for: Dissipative: 10^6 to 10^9 Ω/sq. Conductive: 10^4 to 10^6 Ω/sq.

Note: Verify it is tested at RH 15% (dry conditions). Many materials fail when the humidity drops and the air is dry -1.

3. Thermal Shrinkage (MD/TD)

Why it matters: If the tape shrinks during baking or reflow, the pockets deform and cover tape peels.

The number to ask for: Ideally < 1.0% in both Machine Direction (MD) and Transverse Direction (TD) when tested at 100°C for 30 minutes.

Insight: Polycarbonate (PC) generally offers lower shrinkage than PS.

4. Tensile Modulus (Stiffness)

Why it matters: Thin components (like a 0.12mm thick chip) will cause the tape to "drum" or flex if the modulus is low, leading to cover tape delamination.

The number to ask for: Target > 2,000 MPa. Higher modulus provides a stiffer beam strength to the tape -1.

5. Cleanliness / Ionic Contamination

Why it matters: You don’t want outgassing or residue fogging up optical lenses or corroding leads.

The number to ask for: Halogen-free compliance (per IEC 61249-2-21). Also, look for "Low outgassing" grades if packaging sensors or cameras.

Final Tip: Always store Sheets for carrier tape in the original packaging. Exposure to direct sunlight or high humidity (>65% RH) degrades the mechanical properties and surface resistivity within 6 to 12 months. Check the date of manufacture before converting the sheet into finished reels. Using these technical filters will help you find the right substrate for high-yield SMT assembly.