Browse Prior Art Database

Method to suppress EMI/ESD coupling for component packaging

IP.com Disclosure Number: IPCOM000008473D
Publication Date: 2002-Jun-17
Document File: 7 page(s) / 197K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method to suppress electromagnetic interference/electrostatic discharge (EMI/ESD) coupling for component packaging. Benefits include improved performance.

This text was extracted from a Microsoft Word document.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 42% of the total text.

Method to suppress EMI/ESD coupling for component packaging

Disclosed is a method to suppress electromagnetic interference/electrostatic discharge (EMI/ESD) coupling for component packaging. Benefits include improved performance.

Background

              Many high-speed silicon designs, where current density is high, employ an intermediate thermal dissipation component integrated heat spreader (IHS) to ensure quick thermal dissipation and prevent thermal build-up. The conventional heat spreader (see Figure 1) is placed between the silicon die and heatsink. The IHS is generally manufactured from a thermally conductive metallic alloy.

              The tight coupling required for thermal dissipation is also an efficient means of coupling radio frequency (RF) energy. By reciprocity, the heat spreader acts as a broadband transceiving antenna that can easily receive and transmit RF energy. From the die and package to the heatsink, capacitive coupling provides an efficient RF transfer function. The heat spreader can be excited by EMI or ESD, which induces surface currents to flow and causes radiation in all directions.

              Radiation occurs primarily at discontinuities in the skin or at resonant frequencies. Frequencies that resonate with the heat-spreader geometry produce the highest fields, as this is the point where energy is most efficiently transferred. The geometry of the heatsink is much larger than that of the heat spreader and could lower any resonant frequencies, possibly into a critical test range. Isolation and suppression is important close to the RF source to reduce the possibility of additional coupling. To reduce package/die and heat spreader coupling, inductance (loss) between the package/die and the heat-spreader must be increased.

              Conventionally, all electronic equipment that is sold within the European Union (EU) must possess the CE mark that designates it has passed a required set of test standards. These test requirements include system testing for EMI emissions and ESD immunity. During an EMI test, radiated emissions from the system under test are measured to determine if RF radiation levels fall within the acceptable ranges dictated by FCC (U.S.) and CISPR (EU) regulations.

              During an ESD test, a pulse generated by an ESD simulator is applied to the chassis through contact or air discharge. The European regulations require that the equipment under test (EUT) must continue to operate normally when subjected to +/-4 KV ESD contact discharge on metal surfaces and +/-8 KV ESD air discharge on nonconductive surfaces. For design margins, equipment manufacturers (OEMs) require ESD passing levels of +/-6-8 KV for contact discharge.

              If, at any time during the test, the system shows functional failures that require user interaction to recover, the unit fails the test at that particular voltage level. Examples of the failure symptoms are system freeze (lockup), reboot, blue screen, video or data corruption, and peripheral functional loss.

              To meet future EMI/ESD challen...