UL 796-2020 pdf free download

UL 796-2020 pdf free download.Printed Wiring Boards.
12.1.3 Chromiclsulfuric etchant shall be considered representative of all etchants. Any other acidic or alkaline etchant shall be representative of all etchants except chromic/sulfuric.
12.1.4 A flush-press metal conductor shall be recessed in the base not less than 80 percent of the conductor thickness.
12.1.5 When temperature differences are not involved, a change or variation of imprinting method (such as silk screening to a photographic method, one silk-screening method to another, or one photo-emulsion material to another) shall not always necessitate that a board be tested.
12.1.6 A retest is required for any one or more of the following or similar changes. Tests shall be conducted as indicated in Section 26, Thermal Stress, Section 28, Bond Strength, Section 29, Delamination and Blistering, and Section 27, Flammability, unless otherwise indicated:
a) A change in any process when the temperature on the surface of the board exceeds 100°C (212°F) or the maximum operating temperature of the printed wiring board, whichever is greater.
b) A change in etchant. If the fabricator changes the etchant to chromic/sulfuric, a retest shall be conducted as described in Section 26, Thermal Stress, and Section 2, Bond Strength. When the fabricator changes from any acidic to alkaline etchant (or vice versa) except chromic/sulfuric, testing is not required.
c) The addition of plated contact fingers to an existing process. Testing shall be in accordance with Section 32, Plating Adhesion. The addition of any other metallic surface plating to the conductors, including Immersion Silver, but excluding all other silver (see Silver. Section 102 and Silver Migration Test, Section 35), does not require testing.
d) The addition of plated through holes to an existing process. Testing shall be in accordance with 17.7.1, Section 26, Thermal Stress, Section 29, Delamination and Blistering, and Section 32, Plating Adhesion. The addition of any other metallic surface plating, except silver (see Section ), does not require testing.
e) An increase in the laminating pressure. Testing shall be in accordance with Section 26, Thermal Stress, and Section Delamination and Blistering.
12.2 Multiple-site processing
12.2.1 When the process steps defined in 12.1.6 are performed outside of the manufacturing facility or at the factory of some other fabricator, the following procedure shall be employed in accordance with the requirements for outside processing:
a) SUBCONTRACTING — If the board process steps involve the outside contractor receiving critical materials directly from the material supplier or involve critical steps with temperatures over 100°C or the MOT. UL 796-2020 pdf free download.