CARRIER FOR ELECTRONIC COMPONENTS AND A METHOD FOR MANUFACTURING A CARRIER

Abstract: The present invention relates to a carrier (10) intended for one or several electronic components (14, 15) and comprising spaces (13) provided for said components on at least one surface (11). The carrier (10) comprises at least partly conductive LTCC (Low Temperature Cofire Ceramic) material with good thermal conduction capacity, so that the carrier besides providing mechanical support for the components also conducts heat generated by the components.

Description: Title CARRIER FOR ELECTRONIC COMPONENTS AND A METHOD FOR MANUFACTURING A CARRIER TECHNICAL FIELD The present invention relates to a carrier intended for one or several electronic components, which comprises spaces provided for said components. The invention also relates to a method for manufacturing the carrier. BACKGROUND OF THE INVENTION LTCC (Low Temperature Co-fired Ceramic) tape, e.g Green Tape® from DuPont, is known to be a very good medium when producing carriers for electronic components. The aim of a carrier is mainly to provide mechanical support for the components mounted on it and to allow arrangement of conductor paths. The increasingly reduced size of components has enabled mounting of components inside the carrier or in cavities provided for receiving the components. A major problem within the electronics is the transferring heat generated by the components. Usually, the components are provided with cooling flanges or the like, which result in an additional manufacturing step and require more space. Specially when using MCM (Micro Circuit Material) components, cooling is difficult to accomplish because of the size of the components. The Swedish Patent Application No. 9803204-8 discloses a new method and device for buried components, which eliminates a time consuming and complicated hole making between an upper surface layer of a carrier and the contact points of a component. The carrier is made of, e.g glass epoxy material or ceramic materials. According to the application, vias are used for cooling of components. On the market there are also so called "chip bays", which consist of bays etched in silicon plates. These bays can also be moulded in plastics. However, they have the common disadvantage of conducting heat poorly. Chip bays can also be made of recesses in metal. SUMMARY OF THE INVENTION The object of the invention is to provide a carrier, preferably made of LTCC material, which in a very simple way permit mounting and cooling of electronic components arranged inside or outside the carrier. The important advantage of the invention is that it allows a carrier and a cooling element in the same unit. A second object of the invention is to provide a good ground plate essentially built in the carrier itself. These objects have been achieved through the carrier consisting of at least partly conductive LTCC (Low Temperature Cofire Ceramic) material with good thermal conduction capacity, so that the carrier besides providing mechanical support for the components also removes heat generated by the components. Preferably, the carrier consists of a material comprising glass mixed with metallic particles, permitting refire of the material. Advantageously, said spaces comprise cavities or recesses which surround the components for better thermal conduction. Said components may comprise circuits according to the industrial standard "flip chip", which comprise a first surface and a second surface, which first surface is arranged with one or several contact points for connection to contacting members, which extend out of said space. The second surface is brought into the space and is fastened by means of an adhesive. To provide a carrier with conductor paths, the surface of the carrier which carries the component and a portion of the component may be provided with a dielectric layer, afterwards the dielectric layer is provided with one or several conductor paths, which are connected to said contacting member. In a preferred embodiment, said spaces are made through pressing or stamping. The method according to the invention for manufacturing of a substantially heat conducting electronic component carrier, which consists of a LTCC material and is provided with spaces for receiving one or several electronic components, comprises the steps: producing a suitable piece of LTCC material, producing, at least on a main surface of the piece, at least one space provided for said components, bringing the piece into a substantially solid form, adding adhesive for attaching components, bringing said components into said spaces and fixing them by means of the adhesive, providing said main surface and components with a dielectric layer, producing conductors on said dielectric layer and to connect the conductors to a contacting member connected to said component. BRIEF DESCRIPTION OF THE DRAWINGS In the following, the invention will be described with reference to embodiments shown in the attached drawings, in which: Fig.1 is a schematic cross sectional view through a carrier according to the invention, and FigsJ-5 schematically show different steps of manufacturing of carrier and the mounting of the components. DESCRIPTION OF A PREFERRED EMBODIMENT The carrier 10 as is shown in Fig. 1 consists of an electric conductive material with very good thermal conduction capacity. Less consideration is taken to the dielectric characteristic of the material. Advantageously, such a material is a LTCC material, e.g in the form of a LTCC tape. To obtain these characteristics, the material is assumed to be made of e.g glass mixed with metallic particles, such as copper, aluminium or the like, where the glass essentially surrounds the metallic particles. This results in satisfactorily firing and refiling of a LTCC material. The carrier 10 comprises a first and a second main surface, 11 and 12, respectively. On at least one of the main surfaces, e. g the first one 11 , cavities or recesses 13 are arranged for receiving components 14 and 15. Each component 14 and 15 in turn present a first and a second main surface 20 and 21 respectively, where the first surface 20 is provided with contact points 16. The components can consist of IC circuits, micro MCM, resistor array or the like. Each cavity 13 is designed so that its form substantially corresponds to the component it will receive. Each cavity comprises abottom surface 17 and side surfaces 18. The dimension of the cavity is chosen that when it surrounds the component a very good contact between the surfaces of the cavities and the exterior of the component is obtained and an optimum heat conduction can be achieved. The contact between the surfaces can be amplified, e. g by applying a heat conductive paste or the like of known type on the surfaces. The component is affixed to the bottom surface 17 (or other suitable surface) of the cavity through its second surface 21 by means of e.g an adhesive 19, such as glue, preferably with good thermal conduction capacity. Furthermore, the depth of the cavity should correspond to the thickness of the component (plus the adhesive) so that a plane surface between the first main surface 11 of the carrier and the first main surface 20 of the component is achieved. Normally, the depth of the cavity can vary between about 0.5-0.15 μm. Afterwards, the contact points 16 can be provided with contacting members (not shown), which first end is connected to the contact point 16. The contacting member can comprise a "bump", which permits use of chips according to the industrial standard "flip chip". The Figures 2-5 very schematically show the steps for manufacturing cavities in the carrier and mounting of the components. The carrier 10, which preferably consists of LTCC tape with a suitable thickness, is cut in appropriate lengths. Then, the cavities 13 are pressed or stamped on at least one first main surface 11 of the carrier 10 by means of a tool 22. The tool 22 comprises a plate provided with elevations 23 (or other pattern) corresponding to the cavities 13 for receiving the components on one of the surfaces. Because of the characteristics of the LTCC material, the material flows away during the pressing so that considerably flat surfaces are formed under the pressing tool. During the pressing, the carrier is exposed to heat. Other types of recessing may also be used. To make the carrier keep its form, it is fired (in a conventional way in connection with the firing of the LTCC material). If the carrier comprises several laminates, these are attached together in this step. Afterwards, the adhesive 19 is applied in the cavities 13 where components should be received, as shown in Fig. 3. It is possible to apply other substances, such as paste for thermal conduction, in this step. The adhesive can also be applied on the components. Afterwards, the components 14 and 15 are brought into the corresponding cavities and are pressed so that the surface 20 distanced from the cavity bottom surface, is essentially levelled with the first main surface 11 and constitute a flat surface, as shown in Fig. 4. Then a dielectric layer 24 can be provided on said first main surface 11 of the carrier and over the components 14 and 15 after connecting suitable contacting members 25 to the contact points of the components. Conductor paths 26 can then be arranged in a suitable way on the dielectric layer 24, e.g through sputtering, plating, bonding or the like. The dielectric layer 24 can be applied in liquid form or as a flexible laminate. The contacting member 25 should have such a length that it exceeds the thickness of the dielectric layer so that contact between the contacting members and conductor paths can be obtained. While we have only illustrated and described a preferred embodiment of the invention, it should be realized that several variations and modifications within the scope of the appended claims can occur. REFERENCE NUMERALS 10 Carrier 11 First main surface 12 Second main surface 13 Cavity 14,15 i Component 16 Contact point 17 Bottom surface 18 Side surface 19 Adhesive 20 First component surface 21 Second component surface 22 Tool 23 Elevation/pattern 24 Dielectric layer 25 Contacting member 26 Conductor path

Claims: CLAIMS 1. Carrier (10) intended for one or several electronic components (14, 15) and comprising spaces (13) provided for said components on at least one surface (11), characterized in, that the carrier (10) comprises at least partly conductive LTCC (Low Temperature Cofire Ceramic) material with good thermal conduction capacity, so that the carrier besides providing mechanical support for the components also conducts a heat generated by the components. 2. Carrier (10) according to claim 1, characterized in, that the carrier consists of a material comprising glass mixed with metallic particles. 3. Carrier (10) according to any of the preceding claims, characterized in, that said spaces comprise cavities (13) or recesses. 4. Carrier (10) according to any of the claims 1-3, characte ized in, that the component (14, 15) comprises a circuit according to the industrial standard "flip chip". 5. Carrier (10) according to claim 4, characterized in, that the component (14, 15) comprises a first (20) and a second surface (21), which second surface is arranged with one or several contact points for connection to contacting members (25), which extend out of said space. 6. Carrier (10) according to claim 5, characterized in, that said second surface (21) is brought into the space (13) and attached by means of an adhesive (19). 7. Carrier (10) according to claim 6, characterized in, that the surface of the carrier which carries the component and a portion of the component is provided with a dielectric layer (24). 8. Carrier (10) according to claim 7, characterized in, that the dielectric layer (24) is provided with one or several conductor paths (26). 9. Carrier (10) according to claim 8, characterized in, that the conductor paths (26) are connected to said contacting member (25). 10. Carrier (10) according to claim 3, characterized in, that said spaces (13) are made through pressing or stamping. 11. Method for manufacturing a substantially heat conducting carrier (10) for an electronic component, which consist of a LTCC material and is provided with spaces for receiving of one or several electronic components, characterized in, the steps of: • manufacturing a suitable piece of LTCC material, • manufacturing, at least on a main surface of the piece, at least one space (13) provided for said components, • bringing the piece into a substantially solid form, • adding adhesive (19) for attaching components, • bringing said components into said spaces and fixing them by means of the adhesive, • providing said main surface and components with a dielectric layer (24), • producing conductors (26) on said dielectric layer and • connecting the conductors to contacting members (25) connected to said component. 12. Method according to claim 11, characterized in, that said spaces are made through pressing or stamping. 13. Method according to claim 11, characterized in, that the LTCC material consists of glass mixed with metallic particles.

Inventors: BERGSTEDT LEIF, LIGANDER PER, BERGSTEDT, LEIF, LIGANDER, PER
Applicants: ERICSSON TELEFON AB L M, TELEFONAKTIEBOLAGET LM ERICSSON
Application year: 2000
Main classification: H01L23
IPC codes: H01L21, H01L23