TV Back Covers: Flame Retardance and Dimensional Challenges in Large Thin-Wall Parts

Flow length is the binding constraint

Flow length ratio — flow length divided by wall thickness — frequently exceeds 300 in very large back covers, demanding stable filling at high flow. High flow generally implies lower molecular weight, which weakens impact and flame stability.

Dedicated flame-retardant PC/ABS grades for back covers are therefore balanced specifically between flow and impact rather than taken off the general list.

Dimensional control

Even 0.3% shrinkage variation across a large area produces millimetre-scale warpage. Controls include multi-point gating, balanced mould temperature, extended hold pressure, plus ribs and slight crowning at design stage.

Local wall thickness differences are the main source of warpage; avoid abrupt thick-to-thin transitions.

Flame retardance and cost

Televisions run continuously, so most markets require V-0 or at least V-2 for the enclosure. Export models destined for Europe tighten the halogen-free requirement further.

Common cost reduction keeps the flame rating and thins the wall instead, but that increases filling and warpage difficulty and must be tracked with mould-flow analysis.