IPC 2223C Sectional Design Standard for Flexible Printed Boards Pre-bake times will vary from minimum of 2 hours up to 10 hours for high layer count flex circuit designs. Layer count, stiffeners, and flex circuit construction are factors that will increase the pre-bake time required. ![]() The duration of the pre-bake will vary depending upon the design of the specific parts. It is recommended that the flex PCB parts be pre-baked at 120☌. ![]() The expansion of the steam results in the delamination. The root cause being the conversion of the entrapped moisture to steam at assembly re-flow temperatures. Baking the product prior to packaging does not eliminate the need for pre-baking prior to assembly.įailure to remove all moisture is the primary cause of coverlay delamination, layer to layer delamination, and stiffener delamination. The industry accepted standard is to pre-bake all flex circuits immediately prior to assembly and without exceptions, even if the product has recently been received from the supplier in a vacuum sealed package. This is an inherent property of the materials and is independent of the manufacturer and or the brand of polyimide materials used. Flex & Rigid-Flex Circuit Assembly Pre-Bake Specificationsįlexible Polyimide materials used in the fabrication of flexible and rigid-flex circuits are hydroscopic up to 2-3% by weight and as such require a thorough pre-bake to eliminate all moisture prior to any assembly process.
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