Electrical Drafting Practices

Electrical and Electronics Diagrams

This standard establishes rules, principles and practices applicable to most commonly used electrical and electronic diagrams. It is consistent with national standards and may be used on military work.

Reference Designations for Electrical and Electronics Parts and Equipment

This standard covers the selection, formation and application of reference designations for electrical and electronics parts and equipment. It describes a uniform method of developing and assigning reference designations for the purpose of correlating, identifying and locating discrete items on equipment, diagrams, drawings, parts lists, manuals and other documents. Under no circumstances will reference designations be used to replace other identifications, such as drawing numbers, part numbers, type numbers, model numbers, or stock numbers.

Three kinds of reference designations are included herein, viz - Unit Numbering Method, Location Numbering Method and Location Coding Method. The Unit Numbering Method has a long history of satisfactory use with all types of electrical and electronic equipment. The Location Numbering Method and Location Coding Method permits rapid physical locations of items in large, complex equipments which comprise multiple use of many identical or similar items. These methods shall be applied in such a way that duplicate complete reference designations will not occur in an equipment or system.

Surface Mount Technology

This section covers the design requirements for surface mount technology (SMT) printed wiring boards (PWBs). The requirements discussed in this section accommodate manual or automatic component placement with manual, wave solder, vapor phase reflow, or infrared reflow attachment of components. Refer to MIL-STD-275 or ANSI/WC-D-275 for additional information. PWBs designed to this section also meet the requirements of MIL-P-551 10.

There are three types of PWBs:

    Type 1- single-sided board
    Type 2- double-sided board
    Type 3- multilayer board

Each of these board types may use through-hole and/or surface mount technology. Mixed technology designs (through-hole and SMT) should only be implemented for components not available in SMT configuration.