High Frequency Product.... malfunction when using no clean paste

Do anyone have any experience on assembling high frequency product, 1.8GHz or 2.4GHz.

In our production line, we manufacture 1.8GHz product with using no clean paste (RMA type) for reflow and no clean wire for rework. In our functinal test,either at 25degC or 50degC, no malfunction is observed.

However when switch to 2.4GHz product,we encounter malfunction of the product at 50deg C. The paste we are using is also a no clean one, but of ca.100ppm halide. I just wonder the dielectric constant of the flux residue will vary with the test temp!?

I look up some test book, it state for RF product, cleaning is required, is it true?

Dear all, do you have any comment? Thanks in advance

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