Implantation happens on average 9 days after ovulation, with a normal range of 6-12 days. Some people have suggested that there are some BBT temperature charts which may show signs of implantation such as a triphasic BBT curve (a rise to a third level of temperatures) or an "implantation dip" (a one-day decrease in temperatures about a week after ovulation).
However, there is no sufficient medical evidence available that can reliably determine from the BBT chart alone whether implantation happened or not and there are no reliable enough signs of implantation on the BBT curve.
Neither a triphasic curve nor an "implantation dip" are sufficient enough evidence that pregnancy has happened and it gives too many women false hope.
The three best indicators of a pregnancy are:
Prior to missing your period there are no reliable enough signs of pregnancy on your BBT curve. The best (and some say only) way to diagnose a pregnancy from the BBT curve is to have no period (amenorrhea) 15+ days after ovulation. Anything else is just speculation.