RoHS | November 23, 2005

FR4 can't take the increased temperatures

The increased temperatures that comes with the RoHS directive will be harmful for the well established FR4(Flame Retardant 4) laminate in the PCB industry.
FR4 is a widely used laminate at the PCB market. In a chronicle published in the Swedish electronics journal Elektronik i Norden IPCs European representative, Lars Wallin raises a finger of warning to product owners and electronics designers that the FR4 material won't manage the heating stresses from the new lead free manufacturing processes such as: HAL(with Sn/Cu-alloys with melting points at 227°C and process temperatures of 265-270°C) and soldering pastes with SAC-alloys(with melting points at 217-221°C and process temperatures of 235-245°C depending on which re-melting process you are using).

Something that may be important to keep in mind, and people often are forgetting, is that the material could be exposed to the harmful temperatures a number of times during the manufacturing process. Lars Wallin named as much as seven possible steps the boards has to pass through the manufacturing process that could stress the material.

*Hot Air Levelling (HAL) (sometimes the boards needs to be re-processed in this step)

*Re-melting side one

*Re-melting side two

*Wave soldering

*Removing of defect BGA/CSP

*Soldering of a new BGA/CSP

*Hand soldering of odd components

Lars Wallin points out that it is important for product owners and designers to check with their PCB suppliers and contract manufacturers to find out all the facts about what matters to their specific products. In many cases the laminate may have to be replaced by other types of laminates.


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