Hi Steve, As you stated shimming is one of the methods and another way is to reduce the stencil opening dimension/ solder paste volume but this will lead to whether is it a cleaning or non cleaning process. If cleaning process, whether how effective it is. GA Tan ________________________________ From: Steve Gregory <[log in to unmask]> Date: 7 June 2018 at 6:14:10 AM SGT To: [log in to unmask] <[log in to unmask]> Subject: [TN] High Ball Count BGA's with heavy heat spreader Hi All, I've been one of the lucky ones who hasn't had to deal with high ball count BGA's (1900+ balls) until now. I have a 1936-ball BGA that we are looking to assemble. I was able to get a couple of mechanical samples so that I could use them to dial my reflow profile in. When I got them, if I said I was surprised, that would be an understatement. This thing weighs close to an ounce with the heat spreader (23.133-grams): http://stevezeva.homestead.com/1936_Ball_BGA_with_Heat_Spreader.jpg So I remember reading threads on the Technet about shimming heavy, high ball count BGA's in the corners with something to keep the weight from squishing the balls out and causing shorts, I know that can happen because I have seen it on 1152-ball CBGA's from Xilinx. Is there anybody willing to share some tips about assembling these beasts? At least I have a couple of mechanical samples I can play with before I dive in with live product....these are spendy. Steve -- This email and any attachments are only for use by the intended recipient(s) and may contain legally privileged, confidential, proprietary or otherwise private information. Any unauthorized use, reproduction, dissemination, distribution or other disclosure of the contents of this e-mail or its attachments is strictly prohibited. If you have received this email in error, please notify the sender immediately and delete the original.