Frank- Been buried at work the last week or so, and I don't know if your question was ever answered. I wanted to recommend a vibration text by D. Steinberg <1>, but couldn't find my copy [nor any of our Library's copies] for a couple of days. I finally copied applicable sections of the Steinberg text; I can fax all sheets to you, if you send a FAX number [13 sheets]. Basically, Dave Steinberg presents the Rayleigh Method for finding the natural frequency of a PWB (assembly). After deriving the equations, they are summarized in a Figure depicting 21 possible PWB configurations, where each configuration is a unique set of mechanical constraints applied to rectangular PWBs. The 3 edge constraint types are free, supported edge, and fixed edge. Supported may apply to a mated daughterboard/motherboard connector set on one edge of the PWB. Fixed is usually used on PWB edges held by card guides/locks, etc. One of the equations, for example: (top) edge free, side edges (2) are fixed, and bottom edge is supported. Then natural freq. approximated by- f_n = pi/1.74 { (D/rho) [ {4/(a^4)} + {1/(2* a^2 * b^2)} + {1/(64 * b^4)} ] }^(-1/2) WHERE: f_n = natural freq pi = 3.1416.... D = a plate stiffness factor, which is a simple function of PWB Modulus of Elast., PWB thickness, and Poisson's ratio for PWB [Steinberg gives typical values for each of these!] rho = mass per unit area [which Steinberg also shows you how to calculate] a = length of PWB b = width of PWB All this reads much easier in the text! This text by Steinberg, and his companion text for themal analysis of electronic equipment, are handy references for this type of stuff. Regards, Michael Alderete Aerojet <1> "Vibration Analysis for Electronic Equipment", by Dave S. Steinberg, 2nd Ed. (1988), Wiley-Interscience Publication [John Wiley & Sons], TK 7870 S8218 1988, ISBN = ? Frank Frimpong wrote... -----Original Message----- From: Alderete, Michael Sent: Wednesday, June 16, 1999 6:39 AM To: Alderete, Michael Cc: '0 AlderetePENET' Subject: Vibration Analysis [Question: PWB natural freq = ?] <IPC TN> ------------------------------ Date: Tue, 15 Jun 1999 15:31:33 +0000 From: "Frank K. Frimpong" <[log in to unmask]> Subject: Vibration Analysis Hi netters I've been struggling with this for a while, and then it suddenly occurred to me that if the guys.....and gals of cause, from technet cannot help me with this then no one else can. How does one determine the natural frequency of a PC board? With best Regards Frank Frimpong. ------------------------------