Patent Description:
As is known, the power dissipation and hence the heat evolution of electronic assemblies are increasing with the power-related further development of the electronic structural elements. It is true that these components are becoming smaller but their efficiencies are increasing and hence efforts to remove the thermal energy increase as well. Furthermore, due to their compactness, these electronic elements are positioned in a smaller space so that once again a higher local heat development results. The power dissipations achieved would be possible only with complicated and bulky cooling bodies when employing fan cooling and are therefore unacceptable. In case of large losses, air cooling therefore clearly reaches its limits.

The new high-performance processors deliver about <NUM> to <NUM> W over an area of about <NUM><NUM> and thus achieve a far higher heat flux density. The processor manufacturers predict that a further increase in the waste heat is to be expected in the years ahead. In view of this development, those skilled in the art are considering liquid cooling for such applications. Liquid cooling more effectively dissipates the heat from the electronic assemblies, with the result that a higher power density is possible. Liquid coolers also allow more compact switch cabinets with numerous electronic components and operate very quietly.

An exemplary generic cooling apparatus is disclosed in <CIT>, in which an insert is provided inside a cooling channel, the insert having a plurality of pins forming channels towards a cooler wall and being supplied with coolant via openings in an inclined surface of the inlet which is hit by a coolant flow from the coolant channel.

The document <CIT> discloses a radiator for cooling electronic components.

The document <CIT> discloses a power module comprising a sealed body connected to a heat dissipating member for cooling semiconductors located inside the sealed body.

The invention provides an improved cooler, which, while being as compact as possible, permits a more effective cooling structure and a lighter, simpler design.

By way of example only, preferred embodiments of the invention will be described more fully hereinafter with reference to the accompanying figures, wherein:.

The embodiments described in relation with <FIG> do not form part of the invention but are useful to understand it.

<FIG> shows a first embodiment of a cooler <NUM> according to the invention. The cooler <NUM> has an inlet <NUM> and an outlet <NUM>, a first unit <NUM> and a second unit <NUM>. A first part to be cooled <NUM>, in particular an electronic element, is applied on a first surface <NUM> of the first unit <NUM>. The cooler is fed by the inlet <NUM> with coolant, which distributes in a lower part of the cooler, more or less evenly along a long side of the cooler, and is then guided forth and back through a plurality of channels formed by fins of the first and second unit until it arrives in an upper part of the cooler which accesses the outlet <NUM> where the coolant is discharged. The formations of the inlet <NUM> and/or outlet <NUM> can be part of the first and/or second unit or can be separate elements connectable with the first and second unit. The first and second unit can together form a housing. In a particular embodiment, the first and second unit form a housing together with at least one of a separate inlet, a separate outlet, and a separate wall element.

In the example shown in <FIG>, the fed coolant first comes into contact with a fin of the first unit. However, as well, the first fin to come into contact with the coolant can also be from the second unit. The fins of the first and second unit intertwine, i.e. they are put together such that the fins of the first unit and the second unit alternate. In this way, the coolant is sent forth and back, at every turn impinging on the backside of the plate having the first surface <NUM>. The area of impinging is named "root" in the following. The term "intertwine" is to be interpreted as implying the involved units both (a) having at least in some parts contact and (b) having at least in some parts no contact at all.

To more easily understand the structure, <FIG> shows a section of the second unit of <FIG>. It is noted that such structure is by way of example only. The inventive principle can also be achieved with various other structures, as will be shown below. The fins <NUM> in <FIG> ("second unit fins") have a waved profile. They extend from a root section ("second unit roots") to a front section ("second unit fronts").

<FIG> shows a cross-sectional view along the long side and perpendicular to an alignment of the corrugated structure of the fins. In this situation, the first and second unit are stuck together, which is why the second unit fins <NUM> are visible here as well as first unit fins <NUM>. A particular feature of the embodiment of <FIG> is that a longitudinal orientation of the fins a slight inclination in order to further improve an even longitudinal distribution of the coolant to achieve a uniform pressure drop. However, this inclination is optional and not necessary in all embodiments of the invention. Each of the corrugated structures has for example a waved pattern, a zigzag pattern, a meander pattern, or a trapezoidal pattern.

<FIG> shows a side view such that the long side is essentially perpendicular to the paper level and one can see the single fins <NUM> of the first unit and the single fins <NUM> of the second unit being intertwined. The coolant by which the cooler is fed, arrives below the first fin of the first unit <NUM> on the bottom where it distributes along the long side. The coolant then finds its way around the front section F11 of said first fin to travel between said first fin of the first unit and the first fin of the second unit. This mechanism will be explained more generally for <FIG> below. Said travel between two fins takes place in channels which are formed with a corrugated structure on at least one of the participating fins.

<FIG> shows an example for this formation of channels, which is in accordance with the structure of the fins in <FIG> where the fins of both of the first and second unit have a waved form. <FIG> shows the cross-section view of <FIG> in greater detail from the first unit <NUM> towards the second unit <NUM>. This cross-section view corresponds to the cut plane A indicated in <FIG>. As can be seen in <FIG>, the fins are arranged and abutting one another in such a way that said waves are offset relative to each other to form the channels. That is to say, the reverse channels are shifted by the offset O1 relative to the inbound channels.

A coolant flow is indicated by the full arrows and the dashed arrows. The full arrow flow could be seen from the perspective of the cutting plane A, the dashed arrow flow is a reverse flow actually covered by the fins from this perspective. So, the fins <NUM> are actually cut in this view, and from the fins <NUM> we can see the front section uncut. The area of full arrows is a root (section) of the first unit where a cooling impingement takes place. After the coolant coming from an inbound flow <NUM> frontally impinged on the root, it is split up into two flow parts laterally diverging into reverse channels <NUM> to the next "floor" or "level". This split-up of the single channel flows allows an extra cooling effect which increases the overall efficiency. Apart from the ever first inbound flow in the system, all other inbound flows are reverse flows from a respective preceding inbound flow.

An abstracted cross-sectional side view of the first embodiment is shown in <FIG>. The arrow heads <NUM> indicate a direction from the paper level out of the plane and show an exemplary flow of coolant from the inlet feeding the cooler. The lines <NUM> indicate the flow progress of the coolant through the cooler, i.e. from the inlet <NUM> towards an outlet <NUM>, wherein the arrow heads <NUM> again are directed out of the plane, i.e. perpendicular to the paper level, and indicate how the used coolant is discharged. Of course, the flowing direction of the coolant in the inlet relative to the outlet can also be opposed (from the top to the bottom). In particular, the flow direction in the inlet and/or the outlet is not necessarily perpendicular to the paper level in the view of <FIG>. In this first embodiment, the cooler can cool two parts <NUM> and <NUM> which are arranged on planes of the units <NUM> and respectively <NUM>. These part carrying planes are the opposite sides of the respective roots of the units (see R11, R12 and R21, R22 in <FIG> shows only two fins of the first unit <NUM> and second unit <NUM>, however this only serves the illustration of the coolant flowing principle and of course the respective assemblies can comprise many more fins.

While <FIG> is undescriptive about which fins and/or which side of the fins has a corrugated structure, <FIG>, <FIG> show some of the various possibilities.

The corrugations of the embodiment according to <FIG> are represented by the layout of <FIG>. The double dashed line means both sides of the fins have a corrugated structure, in this case a wave structure. A further possibility of a double-sided structure of fins in shown in <FIG>, wherein the indentations are abutting in an assembled situation (indicated by the arrows). In other words, the structure is not necessarily rounded, it can also have an edged meander-type of shape. The sketches of <FIG>,<FIG>, <FIG>, and <FIG> show the fins being spaced apart, however, these figures are only for demonstration of the constellations, not to show the true dimensions.

A further example is abstractedly shown in <FIG>, where the fins are plates having a smooth surface on one side and having corrugations on the other side. One embodiment for this case is shown in the 3D view of <FIG>, where the corrugated structure is achieved with grooves cut out from a plate, or with bars added to a plate. When the first unit fins and the second unit fins are contacting with an offset regarding their corrugations, they will form inbound channels <NUM> and reverse channels <NUM>. The impingement on the root surface is indicated with the splash symbol and the split-up is indicated with the double-lined arrow showing the flowing direction of the coolant. Why <FIG> is undetermined about a second unit wall or root will be understood when arriving at another embodiment further below. <FIG> shows an example of fin structures that corresponds to the example of <FIG> just the other way around.

A further embodiment of a combination of first and second unit of a cooler is shown with <FIG>, where the second unit can be of a material that is cheaper to manufacture, e.g. plastic. The first unit having a surface for receiving a part to be cooled can be made of a material that has very good thermal conductivity, e.g. aluminium. Machining aluminium with smooth fins is easier compared to the waved-structured fins shown in <FIG>. <FIG> shows on the left said first unit with the smooth plates and on the right the second unit, which (can be, but here) is not intended for receiving a part to be cooled, having a double-sided corrugated structure. The fins of the first and second unit are abutting at least such that the form an inbound channel <NUM>. In particular, the channel <NUM> is at least formed in the area of the second unit fin front, i.e. shortly before the coolant is entering the root area to impinge on the first unit wall. <FIG> shows an example how the fins are abutting and how the coolant is redirected. The reverse channels <NUM> are in this case also starting right at the second unit fronts where the first unit fins are abutting. It would be possible to keep some distance for the reverse flow such that no reverse "channels" are formed but a reverse flow (see <FIG>). It must be noted that most importantly, it is the inbound coolant which is formed by channels in order to impinge on the root area in the form of a jet that will split up or broaden or swirl after it impinged on the root. In the shown example (<FIG>), the reverse flow is immediately introduced in reverse channels <NUM> which are arranged offset to the inbound channels <NUM>. This channel offset O2 is to be understood with reference to an axis which is aligned perpendicular to the channels and parallel to the fins.

<FIG> shows a similar constellation, wherein only the first unit <NUM> has double-sided structured fins and the second unit has plain fins and a second surface for receiving electronics to cool. A person of skill in the art will see that there are various possibilities to apply the inventive principle.

<FIG> shows in an exaggerated sketch that the fins of the first unit have an inclination relative to the fins of the second unit. This is shown with the example of each of the units having double-sidedly structured fins, however other structure constellations may be applicable. <FIG> shows this inclination with a side view of intertwining fins. The inbound channels are only formed shortly before the coolant hits the impingement zone (root) at the respective root. As a result, after impinging, the coolant is not introduced into a reverse channel. However, the inbound channels forming little jets that can impinge on the root still leads to an advantageous cooling effect according to the invention. After impinging, the coolant is whirled around generating turbulences. <FIG> shows how the reverse flow is entering an open duct instead of the offset channels as known from the other embodiments.

<FIG> and the four parts of <FIG> show an embodiment with a first unit <NUM>, a second unit <NUM>, and a third unit <NUM>. The second unit is in this case an insert <NUM> having a both-sidedly corrugated structure. As second unit <NUM> counts every structured fin that is inserted into the cavities (so not only the one labelled in <FIG>, but the whole set). This set of fins <NUM> can be clamped between the first and second unit <NUM>, <NUM>. To fix the second unit <NUM> without clogging the root section, said assemblies <NUM>, <NUM> may have shoulders <NUM> for the fronts of the second unit to abut. However, other means such as notches on the fins of the second unit <NUM> could also be another embodiment for fixating the second unit <NUM> in the assembly. Due to the shoulders <NUM>, the waved fins keep a gap to the roots such that the coolant can flow through the construction as indicated in the lower right part of <FIG>. The coolant is fed between the first unit <NUM> and the third unit <NUM> and splits up into the shown two opposing directions towards the first unit first root and the third unit first root. The second unit <NUM> fins abutting the fins of the first and third unit forms channels in which the coolant is flowing. After impinging on the respective root it flows back on the other side of the second unit fin where channels are formed, too. At the area where the coolant now confronting, it distributes to the next "floor" or "storey", i.e. it flows around the second fins of the first and third unit, where the second unit second fin is again forming inbound channels. This embodiment is also relatively simple to machine while still providing the inventive principle. For example, as second unit, a plastic injection moulding part can be used since it does not need to necessarily have a good thermal conductivity and its purpose is mainly to form the inbound channels and the reverse channels offset to the inbound channels.

Another embodiment is shown with <FIG>, where a second unit <NUM> is a set of corrugated sheets each having a bend in the middle. The first unit <NUM> and the third unit <NUM> are similar to the ones from the embodiment of <FIG>, i.e. ribbed aluminium parts, with the difference that they are arranged offset relative to each other such that the fins can each rest on one of said bends in the second unit fins. In the area of each bend of the second unit fins there is an opening <NUM> for conducting the coolant. In this way, the coolant is guided through this labyrinth in the inventive manner wherein upon impinging the coolant flow is split apart and discharged from the root area in offset reverse channels.

Whatever way the cooler according to the invention might be embodied, a part to be cooled can be applied with the following configuration. The heatsink can be coated with thermally sprayed ceramic as electrical insulation. Between the ceramic layer and the heatsink, an intermediate layer can be applied to relieve the thermal stresses. The semiconductor device (=part to be cooled) can be mounted by means of a thermal paste and a mechanical fixation or by thermally conductive adhesives. With this special attachment, the electronic part is electrically isolated but the generated heat can be dissipated very effectively.

Claim 1:
A cooler comprising an inlet, an outlet, a first unit (<NUM>), a second unit (<NUM>) and a third unit (<NUM>),
- the inlet configured for feeding the cooler with coolant,
- the outlet configured for discharging said coolant,
- the first unit (<NUM>) comprising a first plane for receiving a first part to be cooled and a set of first unit fins forming cavities,
- the third unit (<NUM>) comprising a set of third unit fins forming cavities,
- the second unit (<NUM>) - embodied as insert - having a set of second unit fins (<NUM>) inserted into the cavities formed by the sets of the first and the third unit fins,
- the second unit fins (<NUM>) each having a second unit fins first surface and a second unit fins second surface,
- the insert (<NUM>) having a both-sidedly corrugated structure,
- the second unit fins (<NUM>) abutting the first and the third unit fins forming inbound channels - between the second unit fins first surface and the first and the third unit fins - and forming reverse channels - between the second unit fins second surfaces and the first and the third unit fins - in such a way that
∘ the inbound channels being configured for
▪ forming coolant inbound flows towards roots of the first unit and the third unit and
▪ causing the coolant flows to impinge and laterally widen on the roots of the first unit and the third unit
∘ and that the reverse channels being configured for
▪ forming coolant back-flows after impinging on the respective roots.