I ve received the approval notice for I-765 on june 4th 2015 but havent received the EAD card yet. how long it takes to receive?

Approval of work authorization and production of the EAD card are two separate things. If you are concerned, I would suggest calling USCIS customer service at 1-800-375-5283 and speaking with a representative to confirm your mailing address. If you have been waiting for more than 90 days total for the EAD card, you can at the same tie request a service request be put on the case and an officer will look into the production of the card. In addition, you can sign up for e-alerts on the USCIS website that will give you automatic updates as to when the card has been mailed to you and give you a tracking number so you know when it will arrive.