ASE Global

Cavity Down BGA

L2BGA
CSBGA

Cavity-Down Thermally Enhanced BGA

Cavity-down Thermally Enhanced BGAs is the solution for thermal dissipation requirements of over 6W, as they are designed with the chip seated on to a copper heat sink to absorb the heat more easily. This method desensitizes the performance deviation of the chip size and lowers the thermal resistance of junction-to-case (qJC) which makes the external heat sink or fan work more effectively.

ASE's Cavity-down BGAs are offered through L2BGA and CSBGA. Both open tool and close tool are available. In general, Cavity-down BGAs enhance thermal performance with about 15~20% improvement compared with to a 4-layer PBGA and by 35% compared with 2-layer PBGA. Electrical performance of Cavity-down BGA is significantas well. The reason is attributed to their flexible layout for staggered traces on different layers, shorter VIAS,and better shielding effect out of the copper heat sink. With the heat sink covering the signal traces fully, Cavity-down BGAs provide better resistance to external EMI (electro-Magnetic Interference) noise.

Cavity-Down BGA is an excellent solution for graphic, networking & communication ICs with high-power and high-speed quality performances.

1. Design Guideline for Cavity down BGA - L2BGA, CSBGA

2. Top view

Symbol	Description	Criteria
L3	Min.distance between bond pad edge and die edge	8 mils
L9	The distance between finger edge to ball pad opening edge	45 mil min.
L10	Stagger bond pad pitch	35 um min.
L11	In-line bond pad pitch	50 um.min.
L12	Fiducial mark location	With the rectangular area (R=2.5 mm min.) enclosed by L12

Bond Pad Pitch, Bond Pad Opening, Max Wire Length & Gold Wire

For In-Line Bond Pad Layout

For Stagger Bond Pad Layout

Min. wire length ≥ 889 um (35 mil)

Wire bond angle limitation:
Finger (Inner/Outer) direction must be parallel to wire direction. If it is possible, then the angle should be confined to the parameters as illustrated below.