Idle temps are irrelevant, unless there is a problem with your maximum temps, THEN, and only then, might idle temps matter.
If your idle temperature is 45°C but your maximum temperature under a FULL load, such as running Prime95 (Small FFT option, all AVX options disabled) for 15 minutes, is 85°C or less (Preferably 80°C or less), then there really isn't a problem.
If however your idle temperature (And we have to be careful here, because what exactly IS idle temperature might vary from system to system.) is 45°C and you are exceeding the maximum recommended temperature under a full load, THEN the high idle temperature is indicative of a cooling problem of some kind, whether that is a poor mount job with incorrectly installed or loose mounting hardware, or a bad paste job, or a lack of case airflow, or a fan facing the wrong direction or simply having a cooling system that is just not good enough for the CPU model.
38-42°C doesn't seem out of line for this CPU, especially if you are not exceeding the maximum recommended temperature.
It would probably be a really good idea for you to read this:
Update: September 19th, 2024 Preface The topic of processor temperatures can be very confusing. Conflicting opinions based on misconceptions concerning terminology, specifications and testing leaves users uncertain of how to properly check cooling performance. This Guide provides an...
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And this, in order to gain an understanding of where you should be and what to do if you are not where you should be.
Covering the basics If you found your way here it's likely you are looking for help with basic overclocking. Either that or you're a long time overclocker interested in seeing whether I had any eye opening insights that you may have been lacking. Rest assured, I don't. This is only intended as...
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