2.54mm Box Header and IDC Ribbon: Pitch, Polarity and Pull Strength

The crimp is the product

A perfect board header cannot save a skewed IDC. 2.54mm ribbon must be 2.54mm centers. The red edge is pin 1 and must follow the header key and triangle mark.

Shop-floor checks

• Insulation must be displaced cleanly; the ribbon should enter flat, not wavy.
• Pull-test samples along the axis; “tug twice” is not a method.
• Strain relief covers must latch. Uncovered plugs fail in doors and sliding drawers.
• Pin count must match; do not drop conductors and still fully populate the header.

Polarity

Use keyed shrouds and keyed plugs together. Unkeyed parts leave polarity to operators. Silkscreen pin 1 on the PCB to match the housing mark.

When a harness vendor builds the cable, send them the pin-1 definition from the Junjia drawing — not a verbal “face the notch”.