FR3009985A1 - DEPOSITION OF SOLDER BY CATHODE SPRAYING OR CHEMICAL DEPOSITION - Google Patents

Abstract

A method of depositing a solder thin film (6b, 6c, 6d) on a cathode sputtering or chemical deposition plate heat exchanger component (4, 10). Preferred application to steel heat exchangers.

Description

The present invention relates to the deposition of solder on brazed plate heat exchanger components during the manufacture of the latter.

Usually, solder deposition on aluminum brazed plate heat exchanger components is by plating. This braze plating is not used for brazed plate heat exchanger components made of steel or superalloy. In fact, the nickel-based solder used in this context, because of its low ductility, can not be deposited by plating. As a result, it is necessary to use nickel-based solder powders. To these powders is added an organic binder to thereby obtain a kind of paint which is applied to said components. This known solution does not allow to deposit thin layers of solder, namely layers of a substantially constant thickness less than or equal to 10 lm, while such a thickness would be sufficient to ensure the connection between the components to be joined. The unnecessary thickness of solder causes a collapse of the heat exchanger during soldering. So you need a tool that can take into account this subsidence. This tool is traditionally a spring. However, the springs used are not well suited to the high soldering temperatures necessary for the melting of the nickel-based solder. It is also known to deposit the nickel-based solder in the form of strips. This solution is not satisfactory because the width of the strips is limited and does not cover from a single solder strip the entire surface of the components. This results in a possible overlap of solder strips and the occurrence of overthickness with, in some cases, a detrimental effect on the quality of the assembly of the heat exchanger. An object of the invention is therefore to provide an improved braze deposition process on brazed plate heat exchanger components. According to the invention, this object is achieved in that the solder deposition is carried out by cathodic sputtering (PVD) or by chemical phase deposition (CVD). Cathodic sputtering and chemical phase deposition allow the deposition of thin layers on the components of the heat exchanger. Thus, there is more subsidence of the heat exchanger during brazing.

According to preferred embodiments, the method according to the invention has one, several or all of the following characteristics, in all the technically possible combinations: said component is a separation plate for fluidic circuits; said component is an engraved fluid circuit plate; - The fluid circuit is etched in the plate after deposition of the thin layer; the component consists of stainless steel, duplex steel, carbon steel or a superalloy; the solder is based on nickel; - The solder target used during sputtering is performed by sintering powder or strips. The invention also provides a method of manufacturing a brazed plate heat exchanger matrix, the method comprising the steps of: a) providing brazed plate heat exchanger components, namely, transporting waves fluid, waveguide bars, and fluidic circuit separation plates; b) depositing solder on the separation plates according to the method indicated above; c) leave the waves and bars free of solder; d) stacking said components to thereby form the matrix; and e) brazing the matrix in an oven.

Preferably, this method has one or other of the following characteristics: in step b), the solder is deposited on both sides of the separation plates; at least one additional brazed plate heat exchanger component is provided, namely an engraved fluid circuit plate, this etched circuit being intended to be closed by a closing face of a closure element constituted by a plate of separation or another etched plate and the solder is deposited on the etched face of the etched plate and only on the face of said closure member opposite said closure face according to the method indicated above.

The invention furthermore covers a method of manufacturing a brazed plate heat exchanger matrix, the method comprising the steps of: a) providing engraved fluid circuit plates; b) depositing solder on the single etched face of the etched plates according to the method indicated above; c) stacking said etched plates to thereby form the die; and d) brazing the matrix in an oven. The invention consists, apart from the arrangements described above, in a certain number of other arrangements which will be more explicitly discussed hereinafter with regard to exemplary embodiments described with reference to the appended drawings, but which are not in no way limiting. In these drawings: FIG. 1 is a perspective and exploded view of a heat exchanger matrix during stacking. This matrix is called "mixed" because it is composed, alternately, of wave layers, separating plate and bars, and engraved plate layers, according to an exemplary embodiment of the invention; Figure 2 is an enlarged representation of the area delimited by the circle 9 in FIG. 1; and Figure 3 is an enlarged representation of an area similar to that defined by the circle 9 in FIG. 2 but taken within the matrix so as to visualize the waves in place of the bars. It can be seen in FIG. 1 a portion of a matrix 2 of heat exchanger, according to an exemplary embodiment of the invention, during assembly before brazing. In a manner known per se, once assembled, the die 2 is brazed in an oven, and then fluid distribution heads are attached to the brazed die to form the heat exchanger. This matrix 2 is composed of a mixed stack of fluidic circuit separation plates 4, fluid transport waves 7 and waveguide bars 8, as well as engraved plates 10. The etched plates 10 have fluidic circuits in the form of flushing grooves 11.

It should be noted that the invention is also applicable to other types of heat exchanger matrices. In FIG. 2, there can be seen an enlargement of the area delimited by the circle 9 in FIG. 1. From the bottom of Figure 2, there is shown a portion of a lower bar 8 followed by a portion of a lower etched plate 10 with a lower face 12 and an etched face 14, then a portion of sheet metal separator 4 with a lower face 16 in contact with the lower etched plate 10 and an upper face 18, then a portion of an upper bar 8 and finally a portion of an upper etched plate 10 with a lower face 12. The plates engraved 10 comprise on their etched face 14 a solder deposit 6c and on their lower face 12 a solder deposit 6d. The separating plate 4 comprises a solder deposit 6b only on its upper face 18. In other words, the lower face 16 of the separating plate 4 does not include any solder deposit. The bars 8 are free of solder layer. In FIG. 3, an enlargement of an area similar to that shown in FIG. 2, but taken within the matrix 2 so as to visualize the waves 7 in place of the bars 8. The solder layers 6b, 6c, 6d are located in the same places as in FIG. 2. In the same way as for the 8 bars, waves 7 do not include solder deposit. According to the invention, the solder layers 6b, 6c and 6d are deposited by sputtering. The solder deposits 6c and 6d on the etched plates 10 can be made before or after etching the etched plates 10. Preferably, the solder 6b, 6c, 6d deposited is a nickel-based alloy comprising chromium, silicon, and optionally boron, iron and / or molybdenum. The contents of the various elements are preferably as follows: from 6.5 to 10% by weight of silicon; from 7 to 19% by weight of chromium; from 0 to 4% by weight of boron; from 0 to 5 (3/0 by weight of iron, from 0 to 5% by weight of molybdenum, the remainder being nickel) Components 4 and 10 on which the deposition of solder is preferably made up: either of stainless steel such as AISI 304 and AISI 316, either duplex steel such as duplex 2205 (UNS S31803) or a superalloy based on nickel or cobalt such as Inconel (s), Hasteloy (S) or the Incoloy (s) or carbon steel Preferably, the components 4 and 10 are degreased, mechanically etched, then degreased again with an organic solvent before being coated brazing by sputtering.

In addition, solder targets used in sputtering can be made by sintering from amorphous solder powder or strips. Note that the absence of solder deposit on the lower faces 16 of the separation plates 4 prevents unnecessary solder located at the grooves 11 of the etched plates 10 does not flow into the grooves 11 during brazing. In the context of manufacturing a matrix devoid of engraved plates, that is to say consisting only of bars 8, 7 and 4, the deposition of solder by sputtering or by chemical deposition will be done on both sides of the plates 4, leaving the bars 8 and 7 waves free of solder.

Claims (11)

CLAIMS 1. A method for depositing a thin layer (6b, 6c, 6d) of solder on a brazed-plate heat exchanger component (4, 10), characterized in that the deposition is carried out by cathodic sputtering or by chemical phase deposition. 2. The method of claim 1, wherein said component is a separating plate (4) of fluidic circuits. The method of claim 1, wherein said component is a plate (10) with an engraved fluid circuit (11). 4. A process according to claim 3, wherein the fluidic circuit (11) is etched in the plate (10) after deposition of the thin layer (6b, 6c, 6d). 5. A process according to any one of the preceding claims, wherein the component (4, 10) is made of stainless steel, duplex steel, carbon steel or a superalloy. 6. A process according to any one of the preceding claims, wherein the solder is based on nickel. 7. A process according to any one of the preceding claims, wherein the solder target used in the sputtering is performed by sintering powder or strips. 8. A method of manufacturing a brazed plate heat exchanger matrix (2), the method comprising the steps of: a) providing brazed plate heat exchanger components, namely transport waves fluid (7), waveguide bars (8), and fluidic circuit separation plates (4); b) depositing solder on the separating plates (4) according to the method according to any one of claims 1, 2 or 5 to 7; c) leave the waves (7) and bars (8) free of solder; d) stacking said components to thereby form the matrix (2); and e) brazing the matrix (2) in an oven. 9. A process according to claim 8, wherein, in step b), the solder is deposited on both sides of the separating plates (4). 10.- Method according to claim 8, wherein: - there is provided at least one additional brazed plate heat exchanger component, namely a plate (10) with an engraved fluid circuit (11), this etched circuit being intended for being closed by a closure face of a closure element constituted by a separating plate or another engraved plate; and the solder (6) is deposited on the etched face (14) of the engraved plate (10) and only on the face (18) of said closure element opposite to said closure face according to the method according to any one of the Claims 1 to 7. 11. A method of manufacturing a brazed plate heat exchanger matrix (2), the method comprising the steps of: a) providing plates (10) with an engraved fluid circuit (11); b) depositing solder on the single engraved side (14) of the engraved plates (10) according to the method according to any one of claims 1 or 3 to 7; c) stacking said etched plates to thereby form the die (2); and d) brazing the matrix (2) in an oven.