Power converter package with enhanced thermal management

Details Power converter package with enhanced thermal management Power converter package with enhanced thermal management

2002-04-22

2004-04-20

Tolin, Gerald (Department: 2835)

Electricity: electrical systems and devices

Housing or mounting assemblies with diverse electrical...

For electronic systems and devices

C029S890030, C257S707000, C361S705000

Reexamination Certificate

active

06724631

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to the packaging and assembly of electrical components, and more particularly to the packaging and assembly for power converters with enhanced thermal management, high electrical interconnection density and low profile.
BACKGROUND OF THE INVENTION
Please refer to FIG.
1
.
FIG. 1
shows one approach to package electric components in a power converter according to the prior art. As shown in
FIG. 1
, power-dissipating devices such as
9
b
,
9
d
and a magnetic element
9
c
are mounted directly on a metal base-plate
6
by a thermally conductive insulator
8
for better heat transfer. The power components are electrically connected with a PCB
5
a
by single-lateral leads
12
. The magnetic element
9
c
is electrically connected to PCB
5
a
by leaded terminals. And, other necessary components such as
9
a
,
9
e
are mounted to one side or both sides of the PCB
5
a
. The assembly may be encapsulated within a capsule (not shown), which acts as a heat spreader and mechanical support.
One drawback of the packaging art in
FIG. 1
, however, is that since the power-dissipating devices
9
b
,
9
d
are electrically connected with the PCB
5
a
by the single-lateral leads
12
, it will be difficult to keep these devices co-planar during the mounting process, which would make the overall manufacturing process more complex, and thus would undesirably increase the manufacturing cost. Meanwhile, the leaded electrical connections of power dissipation devices as well as magnetic element will cause high interconnection parasites, which will result in additional connection resistance loss and poor converter performance especially for high current converter packaging. Moreover, the power-dissipating devices
9
b
,
9
d
are comparatively in a bigger footprint, which would inevitably cause a lower power density packaging.
U.S. Pat. No. 5,973,923 discloses another prior art approach to package electronic components in a power converter as shown in FIG.
2
. In the packaging, a thermal connection from a power-dissipating device
22
to the outside is constructed, in which copper coated vias
42
are prepared by the manufacturing process of the PCB
28
. The metal slug
43
of the power-dissipating device
22
is mounted onto the top pad of the copper coated vias
42
, and a metal base-plate
32
is attached to the bottom pad of the copper coated vias
42
through thermally conductive insulators
30
,
104
. Through these copper coated vias
42
, the heat is transferred from the power-dissipating device
22
to the other side of the PCB
28
, and further transferred to the metal base-plate
32
. The magnetic element
26
b
is also mounted on the PCB
28
, and is connected with metal base-plate
32
by a thermally conductive soft pad
34
to enhance the heat transfer.
One drawback of the packaging art in
FIG. 2
, however, is that since the power-dissipating device
22
is mounted onto top-side of the copper coated vias
42
, and the bottom-side of the copper coated via is occupied by the thermal connections
30
,
104
, the assembly reduces the electrical interconnection density of the board
28
. Moreover, heat from the power device
22
will meanwhile be transferred by the copper coated vias
42
to the board
28
, and thereby increases temperature rise of the board
28
.
With increasing power density and current output capability of the power converter packaging, much more power-dissipating devices are to be mounted onto PCB in parallel to satisfy high current output and meanwhile to well control the conduction power losses. Thus more and more PCB lands are to be occupied by power-dissipating devices. Moreover, the power losses from power-dissipation devices and its conductive trace increase abruptly with the increase of the output current. With the increase of power density and output current, how to manage the heat from these power-dissipating devices and how to shorten the interconnection trace therebetween become very critical for power converter packaging.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to propose a packaging technology for power converters to achieve enhanced thermal management, high interconnection density, improved electrical performance as well as low cost.
To address the above-discussed deficiencies of the prior art, the present invention provides, a package for a power converter, a method of packaging a power converter and a sub-package arrangement employed in the package of the present invention. The package includes: (1) a multi-layer circuit board having a first electrically conductive surface and a second electrically conductive surface opposite to the first electrically conductive surface; (2) a heat spreader having at least a heat transfer surface; and (3) a sub-package having at least a power-dissipating chip, which is disposed between one of the electrically conductive surfaces of the multi-layer circuit board and the heat transfer surface of the heat spreader, having a bare top heat-slug in contact with the heat transfer surface of the heat spreader through a thermally conductive insulator to provide a thermally conductive pathway therebetween, and having a plurality of symmetric leads in contact with one of the electrically conductive surfaces of the multi-layer circuit board to provide an electrically conductive pathway therebetween, wherein the plurality of symmetric leads and the heat-slug are disposed in opposite orientations so that the electrically conductive pathway is separate from the thermally conductive pathway.
In one embodiment of the present invention, the plurality of symmetric leads can also be replaced by balls to meet some electrical connection requirements.
In the present invention, the sub-package, magnetic elements and other passive components of the package are fully mounted onto a multi-layer circuit board.
The unique aspect of this packaging concept is that the power-dissipating chips of the package, which are typically power semiconductors, are assembled in advance into the sub-package, therefore enabling the package to have high interconnection density. The sub-package has a bare top heat-slug and a plurality of symmetric leads (or balls), wherein the plurality of symmetric leads and the heat-slug are disposed in opposite orientations. In one embodiment of the present invention, the heat-slug is up-facing and the leads are down-facing. Of course, the heat-slug can also be down-facing and the leads be up-facing.
In the present invention, the sub-package is disposed between the electrically conductive surface of the multi-layer circuit board and the heat transfer surface of the heat spreader. In this way, the first electrically conductive surface of the multi-layer circuit board is adapted to be electrically connected with the leads of the sub-package to provide an electrically conductive pathway therebetween. The heat transfer surface of the heat spreader is adapted to be thermally connected with the heat-slug of the sub-package through a thermally conductive insulator to provide a thermally conductive pathway therebetween. The heat from the magnetic elements can also be transferred to the ambient by the attached heat spreader. Therefore, the electrically conductive pathway is separate from the thermally conductive pathway, which achieves enhanced thermal management and improved electrical performance.
In one embodiment of the present invention, the sub-package further includes control chips and passive chips. For the reason of increased packaging density and improved electrical performance, the power-dissipating chips, control chips and passive chips can be combined into one sub-package together. More specifically, the sub-package with only one chip can be simplified to be a standard surface-mounting package with a bare top up-facing heat-slug.
Another aspect of the present invention provides a method of packaging a power converter including: (1) providing a multi-layer circuit board having at least an electrically conductive surface; (2) providing a he

Affiliated with

Also associated with

Rating

Power converter package with enhanced thermal management does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Power converter package with enhanced thermal management, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Power converter package with enhanced thermal management will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3255302