Try Heller Industrie's website at http://www.hellerindustries.com They have a formula that they offer for free that calculates land pad geometry to component weight to prevent drop off of components during second reflow. If you can't find it, give them a call and they should be able to email it to you.
Hi Dave, as you said Heller has forum showing you how to calculate land pad for component dropped off during second side. Unfortunately I couldn't found it. would you please give me that link, instead of just http://www.hellerindustries.com. Thanks