Recommendation for baking of Flex and Rigid-Flex PCB
Author: FPCissuing time:2018-12-17 16:22:43Pageviews:2150【smallinBig】
Recommendation for baking of Flex and Rigid-Flex PCB
Text labels:flex PCB,Rigid-Flex PCB
Due to the fact that nearly all Flex and Rigid-Flex PCB are constructed with polyimide inside and that this material is highly hydroscopic in its form, it is strongly recommended to bake the boards to reduce the amount of moisture inside the boards before any type of soldering operation. Without such baking there is risk of delaminating, inner-layer separation or cracking of the hole walls.
Below is a recommendation for different surface treatments.
HASL, Lead-free HASL and ENIG
Flexible board:
Minimum 2 hours at 105° C
Rigid and Rigid/Flex PCB’s FR-4 and Polyimide:
PCB's up to 1.0 mm thickness: minimum 2 hours at 120° C
PCB's up to 1.8 mm thickness: minimum 4 hours at 120° C
PCB's up to 4.0 mm thickness: minimum 6 hours at 120° C
Rigid and Rigid/Flex PCB’s with Polyimide / Thermount®:
All PCB thicknesses: minimum 6 hours at 135° C
Dwell or hold time between baking and soldering is dependant upon the storage conditions. At 50 % relative humidity the recommended hold time is maximum 8 hours, yet if the boards can be stored in vacuum or within oven at 35°C, then this 8 hour limit can be prolonged.
Oven conditions
Basking should take place in clean oven to prevent any form of contamination during the baking process. The boards should also be placed in the oven in such a way that the air can circulate freely around the boards during the baking time.
Solderability concerns
All baking can be considered as advanced ageing and therefore may affect the solderability. Therefore the given and temperature above must be seen only as recommendations and the customer shall take responsibility to approve the process
Immersion Tin, Immersion Silver and OSP
Since all of these surface treatments are very sensitive finishes, normal baking is not
recommended.
Baking in vacuum oven (below 50 mbar) may be performed at lowered temperatures and reduced times. In all such cases the customer have there own responsibility to approve their process
2018-12-17
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