| Cavity-Down Thermally Enhanced BGA |
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Cavity-down thermally enhanced BGAs are suited for ICs with thermal dissipation requirements of over 6W like graphics, networking, and computing devices. Chips in cavity-down BGAs are seated onto the copper heat sink to conduct the heat. This method desensitizes the performance deviation of the chip size, and lowers the thermal resistance of junction-to-case ( JC), and makes the external heat sink or fan work more effectively.
ASE's offers several cavity-down BGAs are offered through ViperBGA/ L2BGA, CSBGA, and Tape BGA. Both open tool and close tool are available. In general, cavity-down BGAs enhance thermal performance by 15~20% compared to a 4-layer PBGA and 35% to a 2-layer PBGA. Electrical performance of cavity-down BGAs is also more significant, 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. |
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| 1. Design Guideline for cavity down BGA - ViperBGA/ L2BGA, CSBGA and Tape BGA |
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| 2. Top view |
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| 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 |
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| Bond Pad Pitch, Bond Pad Opening, Max Wire Length & Gold Wire |
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| For In-Line Bond Pad Layout |
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| For Stagger Bond Pad Layout |
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The Min. wire length for CDBGA. 889 um (35 mil)  Min. wire length |
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| Wire bond angle limitation: Finger (Inner/Outer) direction must be parallel to wire direction |
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| Finger length Max. |
angle |
| 10~12 mil |
15° |
| 12~24 mil |
10° |
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| Cavity Down BGA Feature |
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* Ball PAD solder mask defined is requred. |
| * Finger/Ringsolder mask between rings is requred. |
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| Cavity Down BGA Standard Material |
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| Cavity Down BGA Standard Material |
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| Reference: ASE SPEC: 64-01-000-003 standard assembly design rule |
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