Map FFC Contact Faces and Pin Numbering Between Both Connectors

A flat cable can fit both connectors while presenting its conductors to the wrong contact side or reversing the intended pin map. Pitch and position count do not resolve those details. Draw the cable and both connectors in their assembled orientation before releasing the interconnect.

Identify each contact side

Hirose’s FH12 catalog distinguishes top-contact, bottom-contact and vertical configurations. These are different mechanical interfaces within a related connector family. Confirm the exact connector variant rather than inferring contact position from a photograph of a similar part.

For each end, mark the exposed cable conductors, stiffener side, insertion direction and connector contact surface. Show the board surface and viewing direction. Terms such as face up become ambiguous when one board is inverted in the final product.

Trace numbered conductors

Label pin one at both connectors and follow every cable conductor through the actual folds and twists. Keep the connector drawing’s view convention explicit. A bottom-view footprint drawing and a top-view assembly drawing can otherwise produce a false impression of reversed numbering.

Prepare a simple end-to-end connection table before ordering the cable. Include power, ground and any unused conductors. Do not rely on a supplier’s type-A or type-B shorthand without checking the corresponding drawing, since the physical conductor-face definition is what matters.

Review the complete mating dimensions

Check cable thickness, exposed length, stiffener length and insertion depth against both connector specifications. Contact-side compatibility does not establish those other dimensions. Retain the cable drawing and both connector references as one interface package.

Include the installed bend route and strain relief. A cable that makes contact while lying flat may pull partly out when folded into the enclosure. Avoid using connector clamping alone as evidence that the routed cable has adequate mechanical support.

Verify with an unpowered assembly

Inspect conductor orientation and insertion before applying power, then verify the intended continuity map using an appropriate unpowered test. Confirm that adjacent conductors remain isolated. This is especially valuable when the two ends use different board orientations or connector variants.

Photograph the accepted insertion state and include it in assembly instructions. If the cable supplier, connector variant or enclosure route changes, revisit the map. The useful deliverable is an unambiguous physical and electrical interconnect definition, not a purchase description containing only pitch, length and the number of positions. Where both boards use identical connectors, label the assembly views explicitly; visual symmetry does not guarantee that the cable preserves the intended numbering.