Guias de diseño de tarjetas electrónicas

Board Design Guidelines

TABLE OF CONTENTS
Page SECTION 1: INTRODUCTION 1.1 Policy 1.2 Purpose 1.3 Scope SECTION 2: GENERAL DESIGN STANDARDS 2.1 Circuit Layers 2.2 Silkscreen and Component ID 2.3 Panelization and Tab Routing 2.4 Solder Mask 2.5 Tooling Holes SECTION 3: SMT PAD GEOMETRIES 3.1 General Guidelines 3.2 Pad and Component Terminology 3.3 Reflow Pads for 0201 Chips 3.4 Reflow Padsfor 0402 Chips 3.5 Reflow Pads for 0603 and 0805 Chips 3.6 Reflow Pads for 1206 Chips 3.7 Reflow Pads for Tantalum Capacitors 3.8 Reflow Pads for SOIC 3.9 Reflow Pads for PLCC 3.10 Reflow Pads for MELF 3.11 Reflow Pads for BGA SECTION 4: CREATING CAD PARTS 4.1 Component Outlines and Reference Designators 4 4 4 5 5 6 7 7

8 9 10 11 12 13 14 15 16 17 18 19

SECTION 5: COMPONENT PLACEMENT ANDORIENTATION 5.1 General Engineering Requirements 20 5.2 General Placement Guidelines 21 5.3 Fiducials 22 5.4 Component Spacing 23 5.5 Component and Board Orientation 26 5.6 Board Orientation for Wave Solder 28

5.7 5.8 5.9

Component Orientation 29 Capacitor Placement 31 Components Not Recommended for Bottom Placement 31 Page

SECTION 6: TRACE ROUTING 6.1 Trace Routing to Component Lands 6.2 ViaRouting Guidelines SECTION 7: TEST REQUIREMENTS 7.1 General Requirements 7.2 Test Pads 7.3 Test Pad Spacing 7.4 Component Placement 7.5 Test Tooling Requirements SECTION 8: STENCIL REQUIREMENTS 8.1 General Stencil Requirements SECTION 9: THROUGH HOLE AUTO INSERTION 9.1 Board Guidelines 9.2 Axial Components 9.3 Dip Components SECTION 10: AUTOMATED OPTICAL INSPECTION 10.1 Computer IntegratedManufacturing 10.2 Bill of Materials 10.3 Board Design Data SECTION 11: DEFINITIONS SECTION 12: BIBLIOGRAPHY

32 36 38 38 39 41 41 42 43 43 44 45 45 46 47 52

SECTION 1: INTRODUCTION
1.1 POLICY

These design guidelines, along with suitable materials, fabrications, and assembly processes can be applied by engineers and designers to achieve consistently manufacturable, high quality, reliableprinted wiring boards and assemblies. It is the responsibility of the CAD design group to maintain this document. Representatives of all groups involved in the design and manufacturing of the printed wiring boards and assemblies will have the responsibility of reviewing this document for accuracy and usefulness.

1.2

PURPOSE

This document is intended to be used as a guide in the engineering andlayout of printed wiring boards and assemblies. Guidelines are presented to aid in the design of manufacturable and reliable printed wiring assemblies. PCB fabrication and assembly processes in common use are described along with the advantages and limitations concerning their application. Preferred processes and design practices are recommended to optimize the fabrication and assembly processes,as well as identify manufacturing limitations. It is not possible to exhaustively describe the full capability of Altron Inc.’s assembly processes; therefore, electrical and manufacturing engineering should be consulted when processes or design requirements not presented in this document are required.

1.3

SCOPE

The guidelines and requirements in this document apply to the design andmanufacture of printed wiring boards and assemblies. If possible, pad geometry and outer layers should be reviewed by qualified assembly personnel for potential problems. Proper pad design will allow the desired I-R, vapor phase, convection, or wave solder results. (NOTE: ALL DIMENSIONS IN THIS MANUAL ARE EXPRESSED IN INCHES)

Altron Inc.

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Board Design Guidelines

SECTION 2: GENERALDESIGN STANDARDS
The following sections contain design standards common to printed wiring boards. In the case of small and flex type boards, where exceptions to these standards may be required, fabrication and assembly vendors should be consulted and approval sought from the responsible engineering group.

2.1

CIRCUIT LAYERS

All circuit layers, including power and ground layers, will...