一份极好PCB的EMC设计指南+Get+EMC+Right+First+Time.pdf

Table of Contents 1. Grounding and Planes...................................................................................................... 7 1.1 Filters ............................................................................................................................ 7 1.2 Routing ......................................................................................................................... 8 1.3 Plane slots and boundaries .......................................................................................... 9 1.4 Decoupling capacitors ................................................................................................ 10 1.5 Power Distribution Network Impedance .................................................................... 11 2. High Speed Considerations ............................................................................................ 13 2.1 Identifying High Speed Signals ................................................................................... 13 2.2 Impedance .................................................................................................................. 14 2.2.1 Single Ended Characteristic Impedance ............................................................. 15 2.2.2 Differential Impedance ....................................................................................... 16 2.3 Terminations............................................................................................................... 18 2.3.1 Single Ended Terminations ................................................................................. 18 2.3.2 Differential Terminations ................................................................................... 20 2.4 Placement ................................................................................................................... 22 2.4.1 Partitioning ......................................................................................................... 22 2.4.2 Zoning ................................................................................................................. 22 2.4.3 Analog Buffers .................................................................................................... 23 2.5 Routing ....................................................................................................................... 24 2.5.1 Topology ............................................................................................................. 24 2.5.2 Bus Routing ......................................................................................................... 26 2.5.3 Corners ............................................................................................................... 28 2.5.4 Vias ..................................................................................................................... 28 2.5.5 Differential Routing ............................................................................................ 28 2.5.6 Proximity to Board Edge ..................................................................................... 30 2.6 Signal Timing ............................................................................................................... 31 2.6.1 Identifying time-critical signals ........................................................................... 31 2.6.2 Propagation time ................................................................................................ 32 2.6.3 Eye diagram analysis .......................................................................................... 32 2.7 Oscillators / Crystals ................................................................................................... 33 3. Crosstalk ......................................................................................................................... 35 3.1 Identifying Victims and Aggressors ........................................................................ 35 3.2 Layer Assignment ................................................................................................... 35 3.3 Orthogonality ......................................................................................................... 36 3.4 Parallelism .............................................................................................................. 36 3.5 Guarding ................................................................................................................. 37 3.6 Return paths ........................................................................................................... 38 3.7 Receiver Placement ................................................................................................ 39 4. EMC Considerations ....................................................................................................... 42 4.1 General Considerations .............................................................................................. 42 4.2 Components ............................................................................................................... 42 4.2.1 Component selection ......................................................................................... 43 4.2.2 High speed filters ................................................................................................ 43 4.2.3 Unused pins ........................................................................................................ 44 Page 5 of 76 Copyright © 2014 EMC FastPass 4.2.4 Heatsinks ............................................................................................................ 44 4.2.5 Shielded components ......................................................................................... 44 4.3 Power Supply .............................................................................................................. 45 4.3.1 Mains .................................................................................................................. 45 4.3.2 Voltage regulators .............................................................................................. 45 4.3.3 Switching mode power supplies ......................................................................... 46 4.4 Routing ....................................................................................................................... 47 4.4.1 Clock distribution ................................................................................................ 47 4.4.2 Guarding ............................................................................................................. 48 4.4.3 Stubs ................................................................................................................... 49 4.5 System design ............................................................................................................. 49 4.5.1 Chassis grounding ............................................................................................... 49 4.5.2 Cables ................................................................................................................. 50 4.5.3 Connectors ......................................................................................................... 51 4.6 ESD & Safety ............................................................................................................... 52 4.6.1 Connectors ......................................................................................................... 52 4.6.2 Sensitive pins .......................................................................................................... 54 4.6.3 High Voltage ........................................................................................................... 54 5. Design for Test ............................................................................................................... 55 5.1 Test Points .................................................................................................................. 55 5.2 Tooling Pins ................................................................................................................ 55 5.3 Push fingers ................................................................................................................ 56 5.4 Sealing ........................................................................................................................ 56 5.5 AOI .............................................................................................................................. 56 6. Design for Manufacture ................................................................................................. 57 6.1 Stackup ....................................................................................................................... 57 6.1.1 Symmetry ........................................................................................................... 57 6.1.2 Drill pairs ............................................................................................................. 57 6.1.3 Copper balance ................................................................................................... 58 6.2 Design Rules Check ..................................................................................................... 59 6.2.1 Clearance ............................................................................................................ 59 6.2.2 Width .................................................................................................................. 60 6.2.3 Annular Ring ....................................................................................................... 60 6.2.4 Slivers .................................................................................................................. 60 6.2.5 Acid Traps ........................................................................................................... 61 6.2.6 Silkscreen Over Pads ........................................................................................... 62 6.3 Mechanical ................................................................................................................. 62 6.3.1 Mechanical Drawings ......................................................................................... 62 6.3.2 Drill Drawings ..................................................................................................... 63 6.3.3 Slots .................................................................................................................... 63 6.3.4 Mounting holes .................................................................................................. 64 6.3.5 Panelization ........................................................................................................ 64 6.3.6 PCB manufacturing specifications ...................................................................... 65 6.4 Assembly Considerations ........................................................................................... 66 6.4.1 Assembly Flow .................................................................................................... 66 6.4.2 Stencils ................................................................................................................ 66 6.4.3 Panelized Assembly ............................................................................................ 67 6.4.4 Decals ................................................................................................................. 67 6.4.5 Fiducials .............................................................................................................. 68 Page 6 of 76 Copyright © 2014 EMC FastPass 6.4.6 Thermal Relief .................................................................................................... 69 6.4.7 Assembly drawings and BOM ............................................................................. 69 6.4.8 PCB Assembly Specifications .............................................................................. 70 6.5 Manufacturing files .................................................................................................... 71 6.5.1 Gerber ................................................................................................................. 71 6.5.2 NC Drill ................................................................................................................ 71 6.5.3 Pick & Place ........................................................................................................ 71 6.5.4 Test Point Report ................................................................................................ 71 7. Thermal considerations ................................................................................................. 72 7.1 Power Dissipation ....................................................................................................... 72 7.2 Heatsinks .................................................................................................................... 72 7.3 Cooling Areas .............................................................................................................. 73 7.4 Current Carrying Capacity .......................................................................................... 73 8. Helpful Utilities .............................................................................................................. 75 8.1 IPC7351 Land Pattern Calculator ................................................................................ 75 8.2 PCB Fabrication Wall Chart ......................................................................................... 75 8.3 PCB Calculators ........................................................................................................... 75 8.4 Filter Selection Simulator ........................................................................................... 76 8.5 Circuit Simulation Tools ...........................................................