UL 746F:2006 pdf download – Polymeric Materials一Flexible Dielectric Film Materials for Use in Printed-Wiring Boards and Flexible Materials Interconnect Constructions.
15.5.16 Repeat the procedure steps outlined in 15.5.11 — 15.5.15 for the remaining samples.
15.6 Data collection
15.6.1 Record and report the following measurement tesI data:
a) Flexible material buildup thickness and
b) Verification of the 13 mm (0.5 inch) conductor trace average width.
15.6.2 Record and reporl the following test data:
a) The presence of any wrinkles. cracks, blisters, or loose conductors, or any delamination, wrinkles, cracks, blisters, or loose film, adhesive, base material, bonding film. coverlay, or other insulation materials:
1) Prior to thermal shock or oven conditioning;
2) After 240 hours oven conditioning or cooling to room temperature;
3) After 1344 hours oven conditioning or cooling to room temperature;
4) After bending the sample around the 6.4 mm (0.25 inch) mandrel, after releasing the sample from the mandrel, and prior to flattening and allowing the sample to relax; and
5) After bending the sample around the 6.4 mm mandrel, after releasing the sample from the mandrel, and after flattening the sample then allowing the sample to relax.
Note — Disregard evaluation of the sample in the area of the first completely closed turn if six turns are required to establish five completely closed turns.
16 Cold.Bend Test
16.1 Purpose
16.1.1 The purpose of this test method Is to provide a consistent procedure for bending and assessing the integrity and physical endurance of materials intended for flexible applications while at low temperature, following exposure to low temperature conditioning. The test is designed to provide a limited assessment of the bendability and physical fatigue at low temperature conditions of test samples exposed to below ambient Service temperature conditions,
16.2 Compliance criteria
16.21 There shall be no presence of any wrinkling, cracking, blistering, or loosening of any conductor, or any delamination, wrinkling, cracking, blistering, or loosening of any film, adhesive, base materia]. bonding film. coverlay. other insulat ion material as a result of the cold condiboning.
16.3 Test specimens
16.3.1 The test samples shall include the same material components and component thicknesses used to prepare the minimum build.up construction and maximum buildup construction samples tor the Ambient-bend Test, Repeated Flexing Test, and Coverlay Test (if applicable), Sections 15, 17, and 18 respectively.
a) Five (5) samples shall include all material components representing a minimum build-up construction and
b) Five (5) samples shall include all material components representing a maximum build-up construction.
16.3.2 The test sample conductor pattern is shown in Figure 15.1.
16.4 Apparatus or material
16.4.1 A cold conditioning chamber capable of maintaining the specified conditioning temperature of minus 20 ±2.0CC (minus 4.0 ±3.6F) for a minimum of one hour shall be used for this test.
16.4.2 A 6.4 mm (0.25 inch) diameter rigid mandrel maintained at minus 20 ±2.0CC (minus 4.0 ±3.6c) shall be used for this test.
16.5 Procedure
16.5.1 Subject the samples to a stabilization period of a minimum of 24 hours at 23 ±2’C and 50 ±5 percent RH.
16.5.2 Measure the overall construction build-up thickness of five (5) minimum build-up construction samples and of live (5) maximum build-up construction samples In three separate areas on each, where no conductor material resides on the internal or external surfaces of the constructions.
16.5.3 Verify the 13 mm (1/2 inch) conductor trace average width.
16.5.4 Examine the ten samples using normal or corrected 20/20 vision, and record any presence of any wrinkles, cracks, blisters, or loose conductors, or any delamination, wrinkles, cracks, blisters, or loose film, adhesive, base material, bonding film, coverlay, or other insulation material.
16.5.5 Subject the samples to minus 20 ±2.0CC (minus 4.0 ±3.6F) for a minimum of 1 hour.