ENCAPSULATION OF ELECTRONIC COMPONENTS

Abstract: For physical protection and to reduce stress, an electronic device (10) is mounted within a cavity in a housing (14) which constitutes an encapsulating member. The housing is preferably formed as two premoulded piece parts (14a, 14b). A leadframe (12) extends into the housing (14) in the manner of a sandwich constructon. The device (10) may be mounted on a heat sink (16).

Description: ENCAPSULATION OF ELECTRONIC COMPONENTS This invention relates to the encapsulation of electronic components , and is particularly concerned wit h the f ormat i o n o f pac kag e s f or e l e c troni c components which provide physical and environmental protection to the components . It is an object of the present invention to provide an encapsulated device which is protected during transit from the device manufacturer to the end user, as well as during subsequent mounting operations and in-service life . Conventionally, it is the practice to mould electronic components into a solid body of material , f or example plastics material . However , this can place stress on the device or on components of the device . In accordance with the present invention, an electronic device or electronic components are mounted within a cavity in a housing which constitutes an encapsulating member. Preferably, the encapsulating housing is formed in two parts. A leadframe, to which the electronic device or components is/are connected, may extend through the housing in the manner of a sandwich construction. In order that the invention may be more fully understood, two presently preferred embodiments in accordance with the invention will now be described by way of example and with reference to the accompanying drawing which is a schematic cross-sectional view through a package, showing two alternative mounting arrangements within the central housing. As shown in the drawing, an electronic device 10 which may be a semiconductor device or one or more electronic components is connected to a metal leadframe 12 by wires 13. The device 10 is mounted within a housing 14, for example of moulded plastics material, which constitutes an encapsulating member. In the illustrated embodiments the housing 14 is formed in two parts, an upper housing portion 14a and a lower housing portion 14b. In the arrangement shown in the right- hand half of the drawing, the device 10 is connected to the leadframe 12 but is out of direct contact with any part of the housing 14. In the arrangement shown in the left-hand half of the drawing, the device 10 is mounted within an upper cavity but directly onto the lower portion of the housing, which may be metalised or may incorporate an integral, thermally conductive heat sink as indicated at 16. The heat sink 16 is provided radially inwardly of the lower housing portion which here is formed as a block rather than as a shell. The upper and lower portions 14a, 14b of the housing are applied to the leadframe 12 to sandwich the leadframe therebetween, and may be joined to the leadframe by the use of adhesive. Preferably however, the housing portions 14a, 14b are fixed to the leadframe 12 by the use of high frequency vibration which causes local melting of the contact surface of the plastics housing and thus forms a bond with the leadframe. The internal surfaces of the housing portions 14a and 14b are preferably coated with a material which provides electromagnetic and radio frequency isolation of the device. The internal surface of the housing can also be connected electrically to specific leads of the device 10. This could alternatively be provided by the incorporation of a conductive matrix within the pre¬ moulded parts. As shown in the drawing, a guard ring 18 is provided adjacent to the periphery of the leadframe 12 as a protective feature. This guard ring 18 is preferably formed of pre-moulded piece parts extending circumferentially around the package. Test points are indicated at 20 in the region of the guard ring, and one of the formed leads of the package is indicated at 22. The provision of a guard ring of this nature is described and claimed in our patent application GB- 9018764.2.

Claims: CLAIMS : 1. A packaged electronic device comprising an electronic device mounted within a cavity in a housing which constitutes an encapsulating member. 2. A packaged electronic device as claimed in claim 1, in which the housing is formed as two premoulded piece parts. 3. A packaged electronic device as claimed in claim 2, in which the housing parts are of plastics material and are secured to frame means by induced local melting of the housing parts. 4. A packaged electronic device as claimed in any preceding claim, in which a leadframe to which the electronic device is connected extends into the housing in the manner of a sandwich construction. 5. A packaged electronic device as claimed in any preceding claim, in which the electronic device is not in direct contact with any part of the housing. 6. A packaged electronic device as claimed in any of claims 1 to 4, in which the electronic device is mounted on heat sink means. 7. A packaged electronic device as claimed in any preceding claim, in which the internal surface of at least part of the housing cavity is coated with a material which provides electromagnetic and/or radio frequency isolation.

Inventors: GAINEY TREVOR CLIFFORD, GAINEY, TREVOR, CLIFFORD
Applicants: LSI LOGIC EUROP, LSI LOGIC EUROPE PLC
Application year: 1991
Main classification: H01L23
IPC codes: H01L23