multi-leaded power package
Image:SIL9 ST TDA4601.jpg The multi-leaded power package is a style of electronic component package, commonly used for high power integrated circuits, especially for monolithic audio amplifiers. It was derived from single in-line package. The difference is the lead arrangement; multi-leaded power packages usually have the lead bent to zig-zag pattern. Multi-leaded power packages commonly have more than three leads; nine-, thirteen- and fifteen-lead units are common, units with five or seven leads with TO-220 style are also manufactured. A notable characteristic is a metal tab with a hole, used in mounting the case to a heatsink. The physical view of multi-leaded power packages are simply stretched TO-220 packages. Components made in multi-leaded power packages can handle more power than those constructed in TO-220 cases, or even TO3 cases with thermal resistance no less than 1.5 C/W.{{citation |last1=Hopkins |first1=T. |last2=Tiziani |first2=R. |contribution=Transient thermal impedance considerations in power semiconductor applications |title=Automotive Power Electronics 1989 |publisher=IEEE |place=Dearborn, MI, USA, USA |pages=89–97 |year=1989 |doi=10.1109/APE.1989.97162 |s2cid=111154062 |contribution-url=https://ieeexplore.ieee.org/document/97162 }}
One well-known STMicroelectronics brand of this type of package is Multiwatt.{{cite web |url=https://www.st.com/stonline/products/literature/an/1697.pdf |title=AN261 Designing with Thermal Impedance |last1=Hopkins |first1=T. |last2=Cognetti |first2=C. |last3=Tiziani |first3=R. |publisher=STMicroelectronics |date=1988 |url-status=live |archiveurl=https://web.archive.org/web/20171223111402/http://www.st.com/content/ccc/resource/technical/document/application_note/4e/1d/dc/1f/d3/1e/44/4b/CD00003784.pdf/files/CD00003784.pdf/jcr:content/translations/en.CD00003784.pdf |archivedate=2017-12-23 }}
Typical applications
Multi-leaded power packages are heatsinkable, and thus can be used in projects where a large amount of power is being drawn. The top of the package has a metal tab with a hole used in mounting the component to a heatsink. Thermal compound is also used to provide greater heat transfer.
The metal tab is often connected electrically to the internal circuitry; ground and supply connections are common. This does not normally pose a problem when using isolated heatsinks, but an electrically-insulating pad or sheet may be required to electrically isolate the component from the heatsink if the heatsink is grounded or otherwise non-isolated. The material used to electrically isolate the multi-leaded power package, like mica, needs to have a high thermal conductivity.
In applications where vertical clearance is at a premium (such as ISA cards in computers), it is often feasible to bend the leads at a right angle and mount the component flat to the printed wiring board using a screw and nut. This often provides enough surface area to heatsink the component when power dissipation is moderately high.