Hello TechNetters-- I am interested to find out if anyone has had experience with bonded PCB stiffeners. More specifically, we are looking for some relative physical and cost impacts to the option of bonding stiffening material of some nature to the PCB to induce/control pre-assembly flatness instead of installing a post-processing metal bar. We understand that stiffening ability is going to be a function of material and height but have not yet done any calculations on alternatives. In searching for some practical advice, we hope to direct our efforts only at promising (if any) options. The one caveat so far is that in one case, the stiffener will need to be constrained to a max. height of .187" for wave soldering clearance. Other particulars of the situation are as follows: Size---------18"x12"x.090" Material----FR-4 High Tg Useage----Class 2 in a "glass house" enviroment It is not yet known how large an issue this is going to be for us, but considering the size of the cards, we understand the short- and long-term problematic potential that this holds due to the component mix of BGAs, Alloy 42 TSOPs, leadless r-networks, and press fit connectors. Even though there will be an emphasis on copper balancing in every axis, we don't expect that this will be the only solution needed. Any feedback is welcome... Gregg Peroutka Adv Mfg Engr StorageTek--Network Systems Group [log in to unmask] ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ##############################################################