Thank you for contacting Intel community.
Please be noted that I am checking this with my internal team. I will get back to you once i received the answer.
Apologize for the delay in response as we are under migration few days ago and i did not received notification from you.
Sorry to tell you that Intel did not apply ultrasonic washing on our PCB. This means, ultrasonic washing is not Intel standard test method and we do not have the guidelines. You may use the ultrasonic washing method from your end, however, Intel will not be responsible for it.