What this 12-position, 3-row header is for
The 640502-1 is a 12-position, 3-row male header from the MR (Miniature Rectangular) series, on a 4.20 mm pitch — a pitch common for power and signal in wire-to-board applications. The 3-row layout is less common than 2-row for this pitch, so the PCB footprint and mating receptacle are specific: you need a 3-row, 12-circuit MR-series receptacle with latch lock. The tin plating limits mating cycle life to roughly 25–50 cycles; for frequent disconnect duty, a gold-plated variant (like 1318699-3) would be a better fit.
Where the 6 A rating hits its ceiling
The 6 A per-contact rating is at 25°C ambient. Inside a warm enclosure at 85°C, derate to roughly 3–4 A per contact — the polyamide housing (UL94 V-0) and the tin plating both lose current-carrying capacity as temperature rises. Compared to the gold-plated peer 1318699-3 (same 12 positions, 4-row, 5 A rating), the 640502-1 offers 1 A more per contact but with tin plating that wears faster under repeated mating. For a one-time assembly that stays mated, the tin contacts are cost-effective; for a field-service connector that cycles 50+ times, the gold variant is the better choice.