1 Scope

1.1 These requirements apply to rigid printed wiring boards and flexible printed wiring board for use as components in devices or appliances. Compliance with these requirements does not indicate that the product is acceptable for use as a component of an end product without further investigation.

1.2 The flexible printed wiring boards covered by these requirements consist of conductors affixed to insulating base film, with or without a cover-lay film, with midboard connections.

1.3 These requirements do not cover flexible printed wiring boards of laminated-film construction in which the conductors are parallel to each other and are completely covered by the base film with only point-to-point end connections.

1.4 Flexible material constructions and multilayer rigid flex composite interconnect constructions with and without stiffener and adhesive materials shall be investigated in accordance with the Standard for Flexible Materials Interconnect Constructions, UL 796F.

SUMMARY OF TOPICS:

This revision of ANSI/UL 796 dated August 4, 2021 includes the following changes in requirements:

• Update UL/ANSI CEM-3 and FR-4 Types and Editorial Correction; Table 9.1

• Clarification of Test Pattern Requirements; Figure 10.1, 10.10.1, 10.11.1, 17.5.4 and 17.5.5

• Addition of Reference to 13.1.6 in 13.2 Permanent Coatings Program; 13.2.1

• Addition of Non-Plated via Hole Reference to Notes for Figure 14.1

• Addition of Reference to Flammability Only PWBs; 16.2.1 and 17.8.1

• Clarification of HDI Test Program; Table 19.1

• Addition of Reference to Ceramic Base Material Exception 9.1.3; 20.1.2

• Addition of Reference to Annex A Sample Construction Examples; 23.2

• Clarification of Optional Use of Release Agent and Clips; 25.2.4

• Clarification of Foil Thickness Measurements by Microsection; 25.4.1

• Clarification of Tolerances on Conditioning Parameters; 27.3.2, 28.3(title), 28.3.1, 28.3.2, 30.2, 35.2.4 and 35.2.6

• Clarification of HDI Bond Strength, Delamination and Blistering Testing; 34.3.1

• Editorial Updates; 2.4, 25.1.2, 27.2.3, 27.3.2 and 27.3.3