COOLING LIQUID COMPOSITION FOR A LIQUID COOLING SYSTEM FOR COOLING A HEAT GENERATING ELEMENT ARRANGED ON A PRINTED CIRCUIT BOARD

Abstract

A cooling liquid composition for a liquid cooling system for cooling a heat generating element arranged on a printed circuit board (PCB) comprises an aqueous solution comprising a copolymer having a copolymer concentration in a range of 0.05% to 20% by mass.

Claims

1. A cooling liquid composition for a liquid cooling system for cooling a heat generating element arranged on a printed circuit board (PCB), wherein the cooling liquid composition comprises: an aqueous solution comprising a copolymer having a copolymer concentration in a range of 0.05% to 20% by mass.

2. The cooling liquid composition according to claim 1, wherein the copolymer concentration is in the range of 0.06% to 15% by mass, 0.07% to 13% by mass, 0.08% to 12% by mass, or 0.09% to 11% by mass, preferably 0.1% to 10% by mass.

3. The cooling liquid composition according to claim 1 wherein the copolymer comprises 2-Propenoic acid, 2-methyl-, polymer with ethenylbenzene.

4. The cooling liquid composition according to claim 1 wherein the cooling liquid composition comprises copolymer particles having an average diameter in a range of 0.1 m to 0.5 m.

5. The cooling liquid composition according to claim 4, wherein the copolymer particles have an average diameter in the range of 0.15 m to 0.4 m, preferably 0.18 m to 0.35 m.

6. The cooling liquid composition according to claim 1 wherein the cooling liquid composition further comprises a pigment and/or a dye.

7. The cooling liquid composition according to claim wherein the cooling liquid composition further comprises a pigment which does not comprise titanium dioxide, aluminum oxide, or zinc oxide.

8. The cooling liquid composition according to claim 1 wherein the cooling liquid composition further comprises propylene glycol having a concentration of 5% to 80% by mass, preferably 10% to 75% by mass.

9. The cooling liquid composition according to one of the claim 1 wherein the cooling liquid composition further comprises monoethylene glycol, or wherein the cooling liquid composition further comprises a compound selected from the group consisting of glycerol, ethanol, and methanol.

10. The cooling liquid composition according to claim 1 wherein the cooling liquid composition further comprises sodium 2-ethylhexanoate having a concentration of 0.5% to 20% by mass, preferably 1.5% to 15% by mass.

11. The cooling liquid composition according to claim 1 wherein the cooling liquid composition further comprises 5-Chloro-2-methyl-3(2H)-isothiazolone with 2-methyl-3(2H)-isothiazolone having a concentration of 0.005% to 0.15% by mass, preferably 0.01% to 0.1% by mass.

12. The cooling liquid composition according to claim 1 wherein the cooling liquid composition further comprises a mixture of compounds, wherein the mixture of compounds comprises at least two compounds selected from the group consisting of 1,2-Benzisothiazol-3 (2H)-one, N-(3-Aminopropyl)-N-dodecylpropane-1,3-diamine, 5-Chloro-2-methyl-3 (2H)-isothiazolone, and 2-Methyl-3 (2H)-isothiazolone.

13. The cooling liquid composition according to claim 1 wherein the cooling liquid composition further comprises distilled water having a concentration of 10% to 90% by mass, preferably 20% to 80% by mass.

14. The cooling liquid composition according to one claim 1 wherein the cooling liquid composition is opaque or translucent.

15. The cooling liquid composition according to claim 1 wherein the cooling liquid composition further comprises Polyacrylic acid, sodium salt having a concentration of 0.2% to 2% by mass, preferably 0.25% to 1% by mass.

16. A liquid cooling system for cooling a heat generating element arranged on a printed circuit board, wherein the liquid cooling system is configured for generating a flow of a cooling liquid within the liquid cooling system, the cooling liquid comprising the cooling liquid composition according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Further features and advantages of the invention result from the following description which explains the invention in more detail on the basis of embodiments in connection with the enclosed figures:

[0026] FIG. 1 shows a table of components or compounds to be used for producing different exemplary cooling liquid compositions; and

[0027] FIG. 2a shows a schematic diagram of an embodiment of a liquid cooling system for cooling a heat generating element arranged on a printed circuit board; and

[0028] FIG. 2b shows a schematic diagram of components of the embodiment of the liquid cooling system according to FIG. 2a.

DETAILED DESCRIPTION

[0029] FIG. 1 shows a table of components or compounds to be used for producing different exemplary cooling liquid compositions. The first column of the table shown in FIG. 1 indicates the different components or compounds to be used for producing a cooling liquid composition according to a preferred embodiment. In this preferred embodiment, the components or compounds to be used specifically are distilled water, propylene glycol (CAS#57-55-6), styrene/acrylic copolymer (CAS#9010-92-8), sodium 2-ethylhexanoate (CAS#19766-89-3), and 5-Chloro-2-methyl-3(2H)-isothiazolone with 2-methyl-3(2H)-isothiazolone (CAS#55965-84-9) with CMIT:MIT=3:1. The corresponding concentrations in percentages by mass of these components or compounds are indicated in the second column of the table shown in FIG. 1. The third column of the table shown in FIG. 1 indicates different components or compounds that can be used as alternatives for producing cooling liquid compositions according to other different embodiments. The components or compounds to be used for producing the other different embodiments specifically are monoethylene glycol (CAS#107-21-1), glycerol (CAS#56-81-5), ethanol (CAS#64-17-5), methanol (CAS#67-56-1), and a mixture of compounds comprising different active substances, i.e. 1,2-Benzisothiazol-3(2H)-one (CAS#2634-33-5), N-(3-Aminopropyl)-N-dodecylpropane-1,3-diamine (#CAS 2372-82-9), 5-Chloro-2-methyl-3(2H)isothiazolone (CAS#26172-55-4), and 2-Methyl-3(2H)-isothiazolone (CAS#2682-20-4).

[0030] Referring to the table shown in FIG. 1, the styrene/acrylic copolymer (CAS#9010-92-8) is also referred to as 2-Propenoic acid, 2-methyl-, polymer with ethenylbenzene. Further referring to the table shown in FIG. 1, CMIT:MIT indicates the ratio of CMIT (Methylchloroisothiazolinone) and MIT (Methylisothiazolinone).

[0031] In the preferred embodiment, the cooling liquid composition is produced by adding the aqueous solution of the styrene/acrylic copolymer (CAS#9010-92-8) in a concentration of 0.1% to 10% by mass to the mixture of the propylene glycol (CAS#57-55-6) in a concentration of 10% to 75% by mass, distilled (or deionized) water in a concentration of 20% to 80% by mass, the corrosion inhibiting additive sodium 2-ethylhexanoate (CAS#19766-89-3) in a concentration of 1.5% to 15% by mass, and the biological growth inhibiting additive 5-Chloro-2-methyl-3(2H)-isothiazolone with 2-methyl-3(2H)-isothiazolone (CAS#55965-84-9) with the ratio CMIT:MIT of 3:1 in a concentration of 0.01% to 0.1%. The cooling liquid composition according to the preferred embodiment is characterized by a cloudy and/or opaque visual appearance. The size of the styrene/acrylic copolymer particles in the aqueous solution is relatively small, i.e. characterized by an average diameter ranging from 0.18 m to 0.35 m. The styrene/acrylic copolymer provided in the cooling liquid composition according to the preferred embodiment results in a stable cloudy or opaque visual effect for the cooling liquid.

[0032] In this context, it should be noted that concentration values or ranges of the different components or compounds of the cooling liquid composition are always indicated with reference to the mass of the total mixture (and not with reference to the aqueous solution, for example).

[0033] In a further preferred embodiment, Polyacrylic acid, sodium salt (CAS#9003-04-7) can be added to the cooling liquid composition according to the preferred embodiment. Thereby, it is possible to further stabilize the opacifier (i.e. the styrene/acrylic copolymer) in a more demanding environment. In other words, the additional Polyacrylic acid, sodium salt allows to obtain an even more stable cloudy or opaque visual effect for the cooling liquid.

[0034] As an alternative to the use of the biological growth inhibiting additive 5-Chloro-2-methyl-3(2H)-isothiazolone with 2-methyl-3(2H)-isothiazolone, a different biological growth inhibiting additive made from the following active substances may be used: 1,2-Benzisothiazol-3(2H)-one (CAS#2634-33-5), N-(3-Aminopropyl)-N-dodecylpropane-1,3-diamine (#CAS 2372-82-9), 5-Chloro-2-methyl-3(2H)-isothiazolone (CAS#26172-55-4), and 2-Methyl-3(2H)-isothiazolone (CAS#2682-20-4).

[0035] In the other different embodiments, the cooling liquid composition may also be produced by using monoethylene glycol (CAS#107-21-1) instead of propylene glycol (CAS#57-55-6). However, the use of propylene glycol is preferred since thereby, the cooling liquid can be made more environmentally friendly while minimizing the acute poisoning hazard. In addition, producing the cooling liquid composition is not limited to the use of propylene glycol and monoethylene glycol, but can also utilize any of the following anti-freeze additives: methanol, ethanol, and glycerol.

[0036] In embodiments, the cooling liquid can also be coloured by using additional dyes or pigments. Typically, the difference between pigment colouring and dye colouring is that in dye colouring, the dye is fully dissolved in the cooling liquid, while pigment colouring results in a suspension. By the combination of a dissolved dye and the specific aqueous solution comprising the copolymer, it is possible to produce a cooling liquid which is characterized by a stable visual colour effect.

[0037] Contrary to the prior art, the inventive cooling liquid composition prevents that the cooling liquid may suffer from pigment or powder particle retention issues since it is substantially free of titanium dioxide (TiO2), aluminum oxide (Al.sub.2O.sub.3), or zinc oxide (ZnO) particles, or a suspension thereof.

[0038] Embodiments of the invention provide the advantage that the cooling liquid composition does not induce liquid cooling system failures due to a blockage of the cooling channels or a damage to the liquid cooling pump due to a particle built up inside the volute and impeller of the pump.

[0039] Embodiments of the invention also provide a full spectrum corrosion protection for many types of metal, such as aluminum, copper, brass, stainless steel, and are compatible with many types of plastic materials, such as POM, PC, PCCM, PMMA, PPS, ABS, and MABS, which are found inside the liquid cooling system.

[0040] The inventive cooling liquid composition is further characterized by allowing for an easy removal of the dried out stains or spots with water or alcohol.

[0041] FIG. 2a shows a schematic diagram of an embodiment of a liquid cooling system 10 for cooling a heat generating element arranged on a printed circuit board. FIG. 2b shows a schematic diagram of components (i.e. cold plate 12 and heat generating element 22) of the embodiment of the liquid cooling system 10 according to FIG. 2a. As shown in FIG. 2a, the liquid cooling system 10 comprises the cold plate 12, a liquid cooling pump 14 having a liquid reservoir 15 (e.g. an expansion vessel), and a radiator 16. The cold plate 12 may also be referred to as a cooling liquid block. The liquid cooling pump 14 is, for example, a motor-driven pump. The radiator 16 is, for example, a liquid-air heat exchanger and comprises a plurality of fans 18a to 18c. The cold plate 12 and the radiator 16 are connected to the liquid cooling pump 14 by means of flexible cooling tubes 20a to 20c. The embodiment of the liquid cooling system 10 shown in FIG. 2a may be integrated into a casing of a computer (e.g. tower PC) for cooling the CPU thereof.

[0042] In operation, the cold plate 12 may be in thermal contact with the heat generating element 22 arranged on the printed circuit board. The cold plate 12 is configured to absorb the heat generated by the heat generating element 22. This heat absorption process is represented by the arrows Q in FIG. 2b.

[0043] Referring to FIG. 2a, the liquid cooling system 10 generates a flow of a cooling liquid (e.g. the cooling liquid composition according to the previous embodiments) within the liquid cooling system 10. The flow of the cooling liquid is generated by means of the liquid cooling pump 14. The liquid cooling pump 14 pumps the cooling liquid provided by the liquid reservoir 15 such that the flow of the cooling liquid is generated from the liquid cooling pump 14 to the radiator 16 via the flexible cooling tube 20a, from the radiator 16 to the cold plate 12 via the flexible cooling tube 20b, and from the cold plate 12 to the liquid cooling pump 14 via the flexible cooling tube 20c. This flow of the cooling liquid is represented by the arrows P1 to P3 in FIG. 2a.

[0044] The cooling process is characterized as follows. The heat generated by the heat generating element 22 is absorbed by the cold plate 12. The cooling liquid flowing through the cold plate 12 absorbs the heat and transfers the same via the liquid cooling pump 14 to the radiator 16. Within the radiator 16, heat dissipation occurs such that the cooling liquid flowing through the same effectively cools down. For the heat dissipation, the radiator 16 may be in thermal contact with relatively cold air on one side (indicated by the arrows P4), and relatively hot air may be generated on the other side of the radiator 16 (indicated by the arrows P5). The relatively hot air may be blown away by means of the fans 18a to 18c of the radiator 16. Consequently, the heat generating element 22 can effectively be cooled by means of the cooling liquid flowing through the cold plate 12 after the heat dissipation within the radiator 16.