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High Capacitance, Highly Reliable, Multilayer Capacitor Chips

IP.com Disclosure Number: IPCOM000045485D
Original Publication Date: 1983-Mar-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Aakalu, NG: AUTHOR

Abstract

By the geometry described in this article, the thermal expansion mismatch between the multilayer ceramic chip capacitor and the substrate is reduced. The reduction is accomplished by stacking the capacitor sheets orthogonally to the line between the attachment pads instead of the stacking used in the traditional packages. With this stacking arrangement, there is a reduction in the distance between the center of the capacitor and the negative and positive solder pads (DNP). The thermal fatigue life of the solder joint is related to the DNP as follows: Life (cycles)=Constant divided by (DNP)/2/.

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High Capacitance, Highly Reliable, Multilayer Capacitor Chips

By the geometry described in this article, the thermal expansion mismatch between the multilayer ceramic chip capacitor and the substrate is reduced. The reduction is accomplished by stacking the capacitor sheets orthogonally to the line between the attachment pads instead of the stacking used in the traditional packages. With this stacking arrangement, there is a reduction in the distance between the center of the capacitor and the negative and positive solder pads (DNP). The thermal fatigue life of the solder joint is related to the DNP as follows: Life (cycles)=Constant divided by (DNP)/2/.

To accomplish this improvement, there is a notch in each layer of the stack which separates the two electrodes of the capacitor. This is illustrated in Fig. 1. The stacked and fired capacitor 1 has electrodes 2, 3 solder-coated for ease of attachment. Shown at 4, 5 are layers of opposite polarity with notches at the bottom center, which are used as laminae to build the capacitor 1.

In Fig. 2, to illustrate the difference in geometry, a traditional capacitor 6 and the new capacitor 7 are shown attached to a substrate 8. Both of the capacitors are shown to have the same DNP (L1=L2) and hence are equal in the thermal cycle fatigue life, but the new stack capacitor 7 has much higher capacitance than that of the traditional capacitor 6. Thus, for a given capacitance requirement, the life expectancy of the structure is...