WO2011069533A1

WO2011069533A1 - An electronics arrangement

Info

Publication number: WO2011069533A1
Application number: PCT/EP2009/066519
Authority: WO
Inventors: Stefan Andersson; Hans Forsberg
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2009-12-07
Filing date: 2009-12-07
Publication date: 2011-06-16

Abstract

The invention discloses an electronics arrangement (100) comprising a first printed board assembly, a PBA (120, 150), with a first electronics component (121, 151) connected to it. The arrangement (100) also comprises a casing (110) of a heat conducting material, and the electronics arrangement (100) also comprises a heat conducting sheet (130) made of a heat conducting material placed in the electronics arrangement (100) in such a manner that the heat conducting sheet (130) is in contact with the casing (110). The first PBA is placed in the electronics arrangement in such a way that the first electronics component faces the heat conducting sheet (130). Suitably, the casing (110) is arranged to be in direct or indirect contact with the first PBA (120, 150).

Description

AN ELECTRONICS ARRANGEMENT

TECHNICAL FIELD

The present invention discloses an electronics arrangement with improved cooling.

BACKGROUND

A key factor in the design of electronics arrangements today is small form factors. This leads to Printed Board Assemblies, PBAs, with a constantly growing need for high density packing of components and/or devices on them, i.e. high density Printed Circuit Boards, PCBs. One opportunity to achieve high density packing is to stack two or more PBAs on each other, so called Package On Package design, POP. A key issue to solve in using POP methods is cooling, since heat generated by electronic devices and circuitry must be dissipated to improve reliability and prevent premature failure.

Due to heat dissipation issues, POP building methods are limited to low power devices, or, alternatively, the POP design has to be increased in height, which is undesirable. Traditional solutions such as heat sinks or other thermal solutions are complicated to arrange on the lower layers in a POP design, and is hard to include in automated production.

SUMMARY

It is this an object of the present invention to provide an improved solution to cooling in electronics arrangements, such as, for example, POP designs.

Such a solution is provided by the present invention in that it discloses an electronics arrangement which comprises a first printed board assembly, a PBA, with a first electronics component connected to it. The electronics arrangement also comprises a casing of a heat conducting material, and according to the invention, the electronics arrangement also comprises a heat conducting sheet made of a heat conducting material, the heat conducting sheet being placed in the electronics arrangement in such a manner that the heat conducting sheet is in direct or indirect contact with the casing. The first PBA is placed in the electronics arrangement in such a way that the first electronics component faces the heat conducting sheet.

Due to the design of the electronics arrangement of the invention, the heat conducting sheet is able to transfer or conduct heat from the electronics components or devices which are arranged on the PBA or PBAs to the casing, which is also made of a heat conducting material. In this manner, a POP design is enabled which is more compact than previous POP designs.

In one embodiment of the electronics arrangement, the casing is arranged to be in direct or indirect contact with the first PBA.

In one embodiment of the electronics arrangement, the heat conducting sheet is placed in direct or indirect contact with the first electronics component.

In one embodiment of the electronics arrangement, the heat conducting sheet is placed in direct or indirect contact with the first PBA.

In one embodiment of the electronics arrangement, the indirect contact is via a heat conducting material.

In one embodiment of the invention, the first PBA and the heat conducting sheet are essentially flat and arranged in parallel to each other. In one embodiment of the invention, the electronics arrangement also comprises a second PBA which is also essentially flat and which has a second electronics component connected to it. In this embodiment, the first and second PBAs are arranged on opposite sides of the heat conducting sheet, and have their electronics component facing the heat conducting sheet. Suitably, but not necessarily, in such an embodiment, the heat conducting sheet is placed in mechanical contact with both the first and the second electronics component. In one embodiment of the invention, the casing comprises a lid, by means of which the electronics arrangement encapsulates the first and second electronics components.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail in the following, with reference to the appended drawings, in which

Figs 1-5 show various embodiments of the invention. DETAILED DESCRIPTION

Fig 1 shows an exploded view of a first embodiment 100 of an electronics arrangement of the invention. In the embodiment 100, the electronics arrangement comprises a printed board assembly, a PBA 120, which has an electronics component 121 connected to it.

The arrangement 100 also comprises a casing 110 which is made of a heat conducting material, the casing 110 being arranged to be in either direct or indirect contact with the PBA 120. When in operation, the electronics component 121 will generate heat, which must be taken care of in some manner. In order to address this problem, the electronics arrangement 100 also comprises a heat conducting sheet 130, i.e. a sheet made of a heat conducting material, which is placed in the electronics arrangement 100 in such a manner that it., i.e. the heat conducting sheet 130, is in either direct or indirect contact with the casing 10, which is also made of a heat conducting material, in addition, as shown in fig 1 , in the electronics arrangement 100, the PBA 120 is placed in such a way that the electronics component 121 faces the heat conducting sheet 130, which will thus enable the heat conducting sheet 130 to absorb heat generated by the electronics component 121 in a better manner, and to conduct this heat to the casing 110, from where it can be radiated or dissipated. The heat conducting sheet 130 is suitably either in direct or indirect contact with the electronics component 121 .

As indicated in fig 1 , in the embodiment 100 the heat conducting sheet 30 is arranged "below" the PBA 120, below here being used in the sense that when the arrangement 100 is assembled {fig 1 being an exploded view) the heat conducting sheet 130 will be more distant from an upper plate 1 15, a "cover" of the casing 1 0 than the PBA 20 is.

The term "direct or indirect contact" between components has been used a number of times above, and refers to the fact that the components referred to in this way can either be in direct (mechanical) contact with other, or in indirect contact via a heat conducting material, such as a heat conducting paste, or they can be separated by an intermediate layer of, for example, air.

Suitably, but not necessarily, the heat conducting sheet 130 is placed in direct (mechanical) contact with the electronics component 121 , in order to further facilitate the heat transfer to the heat conducting sheet 130. Fig 2 shows an exploded view of a second embodiment 200 of an electronics arrangement of the invention. This embodiment comprises the components shown in fig 1 , and the reference numbers from fig 1 have this been retained in fig 2. However, as opposed to the embodiment 100 of fig 1 , the embodiment 200 has the heat conducting sheet 130 arranged "above" the PBA 120, i.e. so that with reference to the lid or cover 1 15 of the casing 110, the PBA 120 will be more distant from the lid than the heat conducting sheet 130 is. It should be noted that in this embodiment as well, the PBA 120 is arranged so that the electronics component 121 faces the heat conducting sheet 130, and is preferably but not necessarily in direct (mechanical) contact with it.

Fig 3 shows an exploded view of a third embodiment 300 of the invention. This embodiment also comprises the parts shown in fig 1 and 2, which have thus retained their reference numbers, but the embodiment 300 also comprises a second PBA 150, with a second electronics component 151 arranged on or connected to it. In this embodiment, the heat conducting sheet 130 is arranged so that it is interposed in the arrangement between the first PBA 120 and the second PBA 150, which are both arranged so as to have their electronics components 121 , 151 , facing the heat conducting sheet 130. Thus, with renewed reference to the lid or cover 1 15 of the casing 1 0, the first PBA 120 is arranged the closest to the lid 115, followed by the heat conducting sheet 130, and then the second PBA 150, which will thus form a "bottom plate" of the electronics arrangement 300.

Aiso shown in fig 3 is an optional PCB 140, which has as its purpose to be an "interposer" PCB which connects the first and second PBAs 120, 150 with each other, in order to enable signals to pass between those PBAs. The PCB 140 is this equipped with connections such as, for example, so called via connections, or openings for so called board to board connections between the first ands the second PBA 120, 150. As shown in fig 3, the interposer PCB 140 is arranged between one of the PBAs and the heat conducting sheet 130. In order to enable the connections in the PCB 140 to connect the PBAs 120 and 150 with each other electrically, the PCB 140 is equipped with protrusions 141 -143, which are designed to protrude through corresponding holes 141 -143' in the heat conducting sheet 130. It is suitably in these protrusions that the vias or other means of connections between the two PBAs are arranged. It can be pointed out that the holes 141 -143' are shown throughout in the drawings, although they do not have a function in all of the drawings.

Fig 4 shows yet another embodiment 400 of the electronics arrangement of the invention: the embodiment 400 is similar to that of the embodiment 300, but with one difference: the casing 110' in the embodiment 400 lacks the lid or top, thus making it more into an open frame, as opposed to what is shown in figs 1 -3, i.e. a covering casing.

The size and shape of the components in the electronics arrangement of the invention can be varied within the scope of the invention, but preferably, at least the first PBA 120 and the heat conducting sheet 130 are essentially flat, rectangular or square shaped and arranged in parallel to each other. Suitably, both of the PBAs as well as the heat conducting sheet 130 are essentially flat, rectangular or square shaped and arranged in parallel to each other, inside the casing 100.

Naturally, the principle of the invention can be expanded to include a larger number of PBAs and heat conducting sheets than is shown in figs 1 -4: preferably, a design with more than two PBAs will also have more than one heat conducting sheet, so that the principle from figs 3 and 4 of alternating PBAs and heat conducting sheets can be adhered to.

The invention is not limited to the examples of embodiments described above and shown in the drawings, but may be freely varied within the scope of the appended claims.

Claims

1 . An electronics arrangement (100) comprising a first printed board assembly, a PBA (120, 150), with a first electronics component (121 , 151 ) connected to it, the arrangement (100) also comprising a casing (110) of a heat conducting material, the electronics arrangement (100) being characterized in that it also comprises a heat conducting sheet (130) made of a heat conducting material, said heat conducting sheet (130) being placed in the electronics arrangement (100) in such a manner that the heat conducting sheet (130) is in direct or indirect contact with the casing (1 10), and in that the first PBA (120, 50) is placed in the electronics arrangement in such a way that the first electronics (121 , 151 ) component faces the heat conducting sheet (130).

2. The electronics arrangement (100) of claim 1 , in which the casing (1 10) is arranged to be in direct or indirect contact with the first PBA (1 0, 150).

3. The electronics arrangement (100) of claim 1 or 2, in which the heat conducting sheet (130) is placed in direct or indirect contact with the first electronics component (121 , 151 ).

4. The electronics arrangement (100) of any of claims 1-3, in which the heat , conducting sheet (130) is placed in direct or indirect contact with the first PBA (120, 150).

5. The electronics arrangement (100) of any of claims 2-4, in which said indirect contact is via a heat conducting material.

6. The electronics arrangement (100) of any of claims 1 -5, in which the first PBA (120) and the heat conducting sheet (130) are essentially flat and arranged in parallel to each other. 6. The electronics arrangement (100) of claim 5, also comprising a second PBA (150, 120), which is also essentially flat and has a second electronics component (121 , 151 ) connected to it, in which electronics arrangement (100) the first and second (120, 150) PBAs are arranged on opposite sides of the heat conducting sheet (130), with their electronics component (121 , 151 ) facing the heat conducting sheet.

7. The electronics arrangement (100) of any of claims 1-6, in which the heat conducting sheet (130) is placed in direct or indirect contact with both the first and the second electronics component (121 , 151 ).

8. The electronics arrangement (100) of claim 7, in which said indirect contact is via a heat conducting material.

9. The electronics arrangement (100) of any of claims 1-8, in which the casing 1 10 comprises a lid, by means of which the electronics arrangement encapsulates at least part of the rest of the arrangement.