PRINTED WIRING ASSEMBLIES : RELIABILITY STRESS SCREENING
Page 1 Scope . . . . . . . . . . . . . . . . . . . . . . . . 2 2 Field of application . . . . . . . . . . . . . . . . . . . 2 3 Reference . . . . . . . . . . . . . . . . . . . . . . . 2 4 Definitions . . . . . . . . . . . . . . . . . . . . . . . . 2 5 Sampling . . . . . . . . . . . . . . . . . . . . . . . 3 5.1 Sample preparation . . . . . . . . . . . . . . . . . 3 5.2 RSS time planning . . . . . . . . . . . . . . . . . 4 5.3 Reduced RSS process determination . . . . . . . 4 6 Method of RSS . . . . . . . . . . . . . . . . . . . . 4 6.1 Principle . . . . . . . . . . . . . . . . . . . . . . . 4 6.1.1 Initial RSS test . . . . . . . . . . . . . . . . . 4 6.1.2 Optimum RSS process duration . . . . . . . 4 6.1.3 Function test . . . . . . . . . . . . . . . . . . 4 6.1.4 Pass/failure criteria . . . . . . . . . . . . . . 4 6.1.5 Failure analysis . . . . . . . . . . . . . . . . 5 6.1.6 Selection of stress types and stress levels . . . 5 6.2 Applicable stress types . . . . . . . . . . . . . . . 5 6.2.1 Constant high temperature . . . . . . . . . . 5 6.2.1.1 Passive “bake” process . . . . . . . . 5 6.2.1.2 “Bake” process with applied voltage . . . 6 6.2.1.3 “Bake” process with power dissipation . . 6 6.2.2 Low/high temperature cycling . . . . . . . . . 6 6.2.2.1 Passive temperature cycling . . . . . 6 6.2.2.2 Temperature cycling with power dissipation . . . . . . . . . . . . . . . . 6 6.2.3 Vibration and other mechanical stress . . . . 7 6.2.3.1 Fixed frequency sinusoidal vibration . . . 7 6.2.3.2 Swept frequency sinusoidal vibration . . 8 6.2.3.3 Random vibration . . . . . . . . . . . 8 6.2.3.4 Bump . . . . . . . . . . . . . . . . . 8 6.2.3.5 Other mechanical stresses . . . . . . 8 6.2.4 Combination of temperature cycling and random vibration . . . . . . . . . . . . . . . . . . . . 8 6.2.5 Humidity . . . . . . . . . . . . . . . . . . . . 9 6.2.5.1 Constant high humidity and temperature . . . . . . 9 6.2.5.2 High humidity and temperature cycling . . . . . . 9 6.2.6 Operational stress . . . . . . . . . . . . . . . 9 6.2.6.1 Constant operational stress . . . . . . 9 UDC 621.38
Stress screening of electronic hardware
Abstract : This report presents the results of a study to develop quantitative and qualitative techniques for planning, monitoring and evaluating stress screening programs during electronic equipment development and production. A screening and debugging optimization (SDO) model developed on a prior study, RADC-TR-78-55, was revised to include current thermal cycling and vibration screening experience and an adaptive feature was added to allow stress screening program changes based on screening results.
Three-dimensional elasticity problems for the prismatic bar
A general solution is given to the three-dimensional linear elastic problem of a prismatic bar subjected to arbitrary tractions on its lateral surfaces, subject only to the restriction that they can be expanded as finite power series in the axial coordinate z. The solution is obtained by repeated differentiation of the tractions with respect to z, establishing a set of sub-problems . A recursive procedure is then developed for generating the solution to from that for . This procedure involves three steps: integration of the stress and displacement fields with respect to z, using an appropriate Papkovich–Neuber (P–N) representation; solution of two-dimensional in-plane and antiplane corrective problems for the tractions in that are independent of z; and expression of these corrective solutions in P–N form. The method is illustrated by an example.