Driving Backplane Thick Copper Layer Planarization

The patent segments the thick copper layer into multiple sub-layers (first copper layer, second copper layer, third copper layer) with different thicknesses and functions. The first copper layer provides electrical connection, the second copper layer provides mechanical support and reduces surface irregularities, and the third copper layer provides additional electrical connection. This segmentation resolves the contradiction by maintaining the low voltage drop benefit while improving the surface flatness for subsequent processing.

The patent applies local quality by making different regions of the copper layer structure have different properties. The copper layer thickness varies in different areas to provide both low impedance paths where needed and flat surfaces where subsequent processing is required. This localized differentiation allows the structure to simultaneously achieve voltage drop reduction and ease of manufacture.

The thick copper layer is segmented into multiple sub-layers with controlled thicknesses. The second copper layer specifically serves as a planarization layer to ensure uniform surface topology across the driving backplane. This segmentation allows the structure to maintain low voltage drop through the copper layers while achieving uniformity required for precise manufacturing and subsequent film deposition.

The patent uses a composite structure combining multiple copper layers with different thicknesses and potentially different material compositions. This composite approach allows optimization of each layer for its specific function: electrical conductivity in some layers and surface uniformity in others, thereby resolving the contradiction between voltage drop reduction and manufacturing precision.