1 option would be 4 mils thick Ni electroformed, increase the QFN opening on the toe to 10 mils, 7.8 x 10 with corner radii yields 0.55 area ratio. How much space is there between the QFN and adjacent components? If there is .10", a 2 mil step would likely work with a metal squeegee. Bill Kunkle MET Assocs -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Kane, Amol (349) Sent: Wednesday, August 27, 2008 8:13 AM To: [log in to unmask] Subject: [TN] Step Stencil Requirements Dear Technetters, I am looking for some information about using step stencils in production. I have a 16 mil pitch QFN component with 7.8 mil square pads. This gives me unacceptable area ratio using a 5 mil stencil. Looks like I am going to have to use a 3 mil thick stencil with this component. I was thinking of using a 5 mil stencil with a 3 mil step. There are chip components around the QFN device. The board is Lead-Free with ENIG finish. Using a Type 4 solderpaste. I was looking for inputs from folks who are using step stencils on the squeegee types (metal vs. poly), changes in print parameters (speed, pressure, Snap off etc,), board design considerations (keep out areas around the component needing the step), resources I could go thru to obtain more information, stencil houses who specialize in this process, and common pitfalls. Any inputs will be greatly appreciated. Thanks, Amol WARNING: Export Control This document may contain technical data within the definition of the International Traffic in Arms Regulations (ITAR), and subject to the Export Control Laws of the U.S. Government. Transfer of such data by any means to a foreign person, whether in the United States or abroad, without proper export authorization or other approval from the U.S. Department of State is prohibited. CONFIDENTIALITY NOTICE: This e-mail, and any attachments, is for the sole use of the intended recipient(s) and may contain information that is confidential and protected from disclosure under the law. Any unauthorized review, use, disclosure, or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply e-mail, and delete/destroy all copies of the original message and attachments. Thank you. --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------