This document is presented to assist in selecting the test analyzer, test parameters, test data, and fixturing required to perform electrical test(s) on all unpopulated printed boards without embedded components (i.e., resistors, capacitors, etc.).

The users must determine the test parameters and fixturing requirements to test for continuity (open), isolation (leakage/short), and other special characteristics (i.e., impedance, hipot, capacitance, current carrying capacity, etc.) that will satisfactorily evaluate the critical electrical characteristics of specific printed boards. The testing levels listed in this document define some of these parameters.

Purpose

Electrical testing verifies that the printed networks on the boards are interconnected according to design requirements.

Electrical test does not ensure that the board can be assembled or that the board meets all of the customer’s requirements. Many physical characteristics of the conductors (dimensional accuracy, solder mask, conductor geometry and nomenclature registration, presence of holes, etc.) can’t be determined by electrical test. Other checks should be employed to confirm these characteristics.

Introduction

Electrical testing of unpopulated printed boards ensures that the board conforms to the electrical design requirements. This specification defines different levels of test to achieve this purpose. The user and supplier will be responsible to define the testing level necessary for each individual part number.

Electrical testing requires both initial capital investments as well as ongoing recurrent costs. Initially, electrical testing requires an investment in properly trained personnel, hardware, and software. Higher levels of test require more resources and investment. Following this initial investment, handling, testing, performance diagnostics, and rework all affect the recurring cost of electrical tests. In selecting the appropriate test level, technology, equipment, and associated fixturing, a suitable compromise between productivity, features, and costs can be found.

The costs associated with electrical testing can vary dramatically, from a few cents for fixture test probes to hundreds of thousands of dollars. Costs alone, however, should never be the only criteria for selecting an automatic test equipment (ATE) system. As shown in Figure 1-1, many other important areas require consideration. For example, spacing and density may be of paramount importance to one user, while another may be concerned with testing parameters and service reliability. Look carefully at all areas of concern and how they may affect each other, not just how they perform individually. Whatever the selection criteria may be, qualifying ‘‘benchmarks’’ should be performed on known product. Furthermore, contingencies covering specific requirements should be included in any purchase order prior to any major equipment purchase.

In addition, electrical testing data can be used to control and improve the printed board manufacturing process.

Selection of the Proper Test Level

All testing levels defined in this document are intended to check electrical functionality of design. However, the test level specified will affect test comprehensiveness. For example, when selecting test voltages and resistances for the PCB, you must take into account both the final application of the board and the level of defect analysis needed to ensure acceptable product. Electrical testing parameters that allow high productivity could also allow high defect escape rates; therefore resulting in higher assembly rework costs. On the other hand, unnecessarily stringent test parameters necessitate excessive capital equipment costs but may not be justified by the potentially higher defect capture rate and lower yields.

It is the responsibility of the customer to select the test level desired. If nothing is specified, IPC Class I, II, and III will be tested to Level A, B, and C respectively.