PCB Stackup Design Considerations for Intel® FPGAs

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ID 683883
Date 6/28/2017
Public
Document Table of Contents
Document Table of Contents x
1. PCB Stackup Design Considerations for Intel® FPGAs
1. PCB Stackup Design Considerations for Intel® FPGAs x
1.1. PCB Stackup Construction 1.2. Material Selection 1.3. Glass Transition Temperature 1.4. PCB Stackup Design 1.5. PCB Panelization 1.6. Conclusion 1.7. Specific Recommendations for Intel® FPGA Devices 1.8. References 1.9. Document Revision History
1.2. Material Selection x
1.2.1. Material Loss Considerations
1.2.1. Material Loss Considerations x
1.2.1.1. Relative Dielectric Constant 1.2.1.2. Loss Tangent 1.2.1.3. Fiberglass Weave Composition 1.2.1.4. Skin Effect
1.4. PCB Stackup Design x
1.4.1. Layer Count 1.4.2. Signal Layers 1.4.3. High Speed Signal Layer Planning 1.4.4. Power and Ground Layers 1.4.5. Power Plane and Capacitor Placement Strategy 1.4.6. Planar Capacitance and Spreading Inductance 1.4.7. Plane Layer Separation 1.4.8. Copper Weight 1.4.9. Hybrid Construction
1.4.5. Power Plane and Capacitor Placement Strategy x
1.4.5.1. General Rules for Capacitor and Power Plane Placement 1.4.5.2. Rules for Transceiver Power Plane Placement 1.4.5.3. Rules for High-Current Power Rails 1.4.5.4. Rules for PLL and Other Power Rails
1.7. Specific Recommendations for Intel® FPGA Devices x
1.7.1. Stratix® 10 Device Recommendations 1.7.2. Stratix® V Device Recommendations 1.7.3. Stratix IV Device Recommendations 1.7.4. Arria® 10 Device Recommendations 1.7.5. Arria® V Device Recommendations 1.7.6. Arria II Device Recommendations 1.7.7. Cyclone® 10 Device Recommendations 1.7.8. Cyclone® V Device Recommendations 1.7.9. Cyclone® IV Device Recommendations 1.7.10. Cyclone III Device Recommendations
1.7.1. Stratix® 10 Device Recommendations x
1.7.1.1. Stratix® 10 Device Family Power Plane Placement Example
1.7.2. Stratix® V Device Recommendations x
1.7.2.1. Stratix® V GX, GT, and GS Family Power Plane Placement Example 1.7.2.2. Stratix® V E Family Power Plane Placement Example 1.7.2.3. Stratix® V Transceiver Channel Breakout Recommendations
1.7.3. Stratix IV Device Recommendations x
1.7.3.1. Stratix IV GX and GT Family Power Plane Placement Example 1.7.3.2. Stratix IV E Family Power Plane Placement Example
1.7.4. Arria® 10 Device Recommendations x
1.7.4.1. Arria® 10 Device Family Power Plane Placement Example
1.7.5. Arria® V Device Recommendations x
1.7.5.1. Arria® V Device Family Power Plane Placement Example
1.7.6. Arria II Device Recommendations x
1.7.6.1. Arria II GX Family Power Plane Placement Example
1.7.7. Cyclone® 10 Device Recommendations x
1.7.7.1. Cyclone® 10 LP Device Family Power Plane Placement Example
1.7.8. Cyclone® V Device Recommendations x
1.7.8.1. Cyclone® V Device Family Power Plane Placement Example
1.7.9. Cyclone® IV Device Recommendations x
1.7.9.1. Cyclone® IV GX Family Power Plane Placement Example 1.7.9.2. Cyclone® IV E Family Power Plane Placement Example
1.7.10. Cyclone III Device Recommendations x
1.7.10.1. Cyclone III Family Power Plane Placement Example
1. PCB Stackup Design Considerations for Intel® FPGAs

1.4.8. Copper Weight

A copper foil is specified in terms of its weight in ounces per square foot (oz/ft2), although it is more commonly referred to in ounces (oz). Typical PCB copper weights are 0.5 oz, 1 oz, and 2 oz. Below table lists the corresponding copper thicknesses for various copper weights.

Table 4.  Copper Weight and Thickness
Copper Weight (oz) Thickness (μm) Thickness (mil)
0.5 17.5 0.7
1 35 1.4
2 70 2.8
Half-ounce copper is typically used for signal traces and one-ounce copper is used for plane layers. Denser copper weights can be used for power delivery if higher DC current is expected. However, thicker copper layers increase the overall board thickness and raise manufacturability concerns related to lamination and drilling. For high frequency signals, increasing the copper weight does not significantly improve the signal loss from trace resistance because of the skin effect. Instead, use wider traces on either half- or one-ounce copper. The current carrying capacity in copper is determined by the allowable temperature rise above ambient resulting from the current flowing through it. Below table list the current rating for different copper weights extrapolated from graphs published in the military standard specification, MIL-STD-275E. You can use these tables to appropriately size your power delivery structures. For example, to pass 10 A of current on 1 oz surface copper layers, you must use at least 200 mil wide copper trace to maintain at most a 20° C rise in temperature above ambient for the conductor.
Table 5.  MIL-STD 275E External Layer Current Capacity Rating
Trace Width (mil) Temperature Rise Above Ambient
10° C 20° C 30° C
Copper Weight (oz/ft2)
0.5 1 2 0.5 1 2 0.5 1 2
Maximum Current (A)
10 0.5 1.0 1.4 0.6 1.2 1.6 0.7 1.5 2.2
15 0.7 1.2 1.6 0.8 1.3 2.4 1.0 1.6 3.0
20 0.7 1.3 2.1 1.0 1.7 3.0 1.2 2.4 3.6
25 0.9 1.7 2.5 1.2 2.2 3.3 1.5 2.8 4.0
30 1.1 1.9 3.0 1.4 2.5 4.0 1.7 3.2 5.0
50 1.5 2.6 4.0 2.0 3.6 6.0 2.6 4.4 7.3
75 2.0 3.5 5.7 2.8 4.5 7.8 3.5 6.0 10.0
100 2.6 4.2 6.9 3.5 6.0 9.9 4.3 7.5 12.5
200 4.2 7.0 11.5 6.0 10.0 11.0 7.5 13.0 20.5
250 5.0 8.3 12.3 7.2 12.3 20.0 9.0 15.0 24.0
300 5.8 9.8 - 8.2 13.8 - 10.1 17.0 -
350 6.4 11.1 - 9.3 15.2 - 11.3 19.6 -
400 7.0 12.0 - 10.0 16.7 - 12.6 21.2 -
Table 6.  MIL-STD 275E Internal Layer Current Capacity Rating
Trace Width (mil) Temperature Rise Above Ambient
10° C 20° C 30° C
Copper Weight (oz/ft2)
0.5 1 2 0.5 1 2 0.5 1 2
Maximum Current (A)
10 0.25 0.4 0.63 0.35 0.54 0.85 0.42 0.64 1.1
15 0.36 0.55 0.88 0.44 0.7 1.2 0.57 0.9 1.6
20 0.41 0.67 1.15 0.55 0.86 1.5 0.65 1.18 1.7
25 0.49 0.75 1.3 0.63 1.1 1.75 0.76 1.38 2.15
30 0.58 0.78 1.5 0.72 1.25 2.0 0.88 1.62 2.5
50 0.80 1.4 2.1 1.18 1.80 3.00 1.25 2.20 3.75
75 1.08 1.9 2.83 1.45 2.75 4.0 1.75 3.5 5.0
100 1.32 2.2 3.5 1.75 3.1 5.0 2.2 3.9 7.2
200 2.2 3.60 5.8 3.0 5.15 8.0 3.8 6.50 10.5
250 2.5 4.20 6.8 3.6 6.30 10.0 4.3 7.50 12.4
300 2.9 4.80 - 4.1 6.90 - 5.2 8.50 -
350 3.3 5.60 - 4.6 7.70 - 5.8 9.80 -
400 3.6 6.00 - 5.2 8.70 - 6.4 10.6 -
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