Online proceedings - EDA Publishing Association

24-26 September 2008, Rome, Italyis able to compensate the smearing effect of Eq. (9). We canprove this by convolving the weight function and its inverse,according to Eq. (10). The result is shown in Fig. 6. Bycomparing with the original weight function we canconclude that the resolution is enhanced by a factor of about2.6.Fig.7. Measured step-function response and its derivativeFig.5. The inverse weight functionFirst we convolve the da/dz derivative with the inversefunction shown in Fig. 5. The result is plotted in Fig. 8. Allthe four time constants appeared correctly, in the form offour peaks. Thereafter we truncated da/dz at t = 25 ms andapplied the inverse function to the remainder part. Thisoperation resulted in the function shown in Fig. 9. It can beconcluded that the reconstructed function is truncated att = 2.2 ms but the remaining part is exactly the same as inFig. 8. If the transient response is measured until a given t xtime instant, then we are able to reconstruct the exact 2 timeconstant spectrum till 0.09 t x . Thus, in order to investigatethe time-constants of the 0.1…10 ms range (which ischaracteristic for the die attach quality) it is enough tomeasure the transient till 120-150 ms. This time requirementcould be acceptable for in-line testing as well.Fig. 6. The function giving the overall resolution and the (9) weight functionLet us now to apply this inverse function to a realmeasured response. We measured the response of an RCnetwork having four time constants: 0.11, 0.45, 1.9 and 8.3ms. The measured step-function response a(z) and itsderivative da/dz are shown in Fig. 7.Fig. 8. Result of the deconvolution2 But, of course, with a limited resolution.©EDA Publishing/THERMINIC 2008 23ISBN: 978-2-35500-008-9