EP3003583A1 - Specific device for cleaning electronic components and/or circuits - Google Patents

Abstract

The invention relates to a device (1) for cleaning electronic components and/or circuits (6). Said cleaning device comprises a first vessel (2) containing a liquid, support means (8), a fluid injection system comprising nozzles (10) allowing the projection of jets of fluid, means allowing the jets from the nozzles (10) to sweep the surface of the components (6), and a fluid mixer (16) comprising a first inlet (161) suitable for receiving a pressurised liquid, a second inlet (162) suitable for receiving a pressurised gas, and an outlet (163) designed to supply the injection system with two-phase fluid, the first inlet (161) being coupled to the outlet (163) by means of an inner duct, the second inlet (162) being coupled to a pressurised gas supply and to an injector for injecting said gas into the inner duct.

Description

 SPECIFIC DEVICE FOR CLEANING COMPONENTS AND / OR

 ELECTRONIC CIRCUITS

The present invention relates to a specific device for cleaning components and / or electronic circuits such as for example electronic boards or substrates based on silicon.

 The present invention may find application, for example, but not exclusively, in the field of microelectronic production. The invention can also find applications in the field of electronic production. Indeed, for example during a welding phase Surface Mounted Components "CMS" in a welding oven, cream or solder residues are formed and remain glued either on the surface of the card or on the components that can cause malfunctions of the electronic card. It is therefore advisable to clean the board after welding operations.

 The cleaning of components and / or electronic circuits having previously undergone, for example, welding or gluing steps, requires efficient cleaning devices and processes.

 The solder residues on an electronic card are particularly difficult to remove by the complex topography of an electronic card but also by its fragility.

 US Patent No. 6,454,867, entitled "Method and Machine for Cleaning Objects in Plate Form" discloses a machine and its cleaning method for cleaning electronic boards of their residues using an immersion technique. Said machine comprises a washing tank where the object to be washed is totally immersed in a vertical position and is parallel to the walls of the washing tank. The latter is filled with a liquid azeotropic liquid cleaning fluid. In order to reduce the costs but also the environmental impact of such a device a recovery system and a cleaning liquid filtering system allow the circulation and filtering of the liquid in a closed loop.

In order to improve the efficiency of the washing, the method proposed by the patent US Pat. No. 6,454,867 implements an ultrasound generator in the wash tank to facilitate the stalling of the particles to be removed. This technique greatly improves cleaning quality but can not be used for cleaning electronic boards dedicated to avionics. Indeed, the presence of many high-tech electronic components and especially components such as quartz makes the use of ultrasound prohibited by regulation.

 In addition, such techniques encounter difficulties in the removal of certain residues such as glue on screen-printing masks or in difficult access areas such as for example in an integrated circuit.

 The invention therefore aims to overcome these disadvantages. More particularly, the invention aims to allow the cleaning of components and / or electronic circuits soiled by residues of different densities, sizes and natures and in particular glue or solder cream. In particular, the invention aims to allow the removal of residues placed in places difficult to access such as under an integrated circuit of an electronic card. Advantageously, the invention can be implemented in the field of avionics. It will also preferably eliminate residues in via holes in printed circuit boards. The invention thus aims to increase cleaning performance and elimination of residues on electronic boards for applications in avionics, for example, or on semiconductor components deposited on substrates based on flexible Kapton.

 For this purpose, the invention proposes a specific device for cleaning components and / or electronic circuits comprising:

 a first tank containing a liquid,

 - Support means for immersing the components and / or the electronic circuit in the first tank,

 a fluid injection system comprising nozzles for projecting fluid jets onto the components and / or the electronic circuit to be cleaned,

 means for the jets of fluid coming from the nozzles to sweep the surface of the components and / or the electronic circuit to be cleaned.

According to the present invention the cleaning device further comprises a fluid mixer having a first inlet adapted to receive a pressurized liquid, a second inlet adapted to receive pressurized gas, an outlet adapted to supply two-phase fluid to the injection system, the first inlet being coupled to the outlet to using an internal pipe, the second inlet being fed with gas under pressure and connected to an injector for injecting said gas into the internal pipe.

 The mixer proposed here for the cleaning device makes it possible to produce a two-phase fluid in which the gas is intimately mixed with the liquid and forms therein microbubbles. The use of a jet of such a two-phase fluid for cleaning components and / or electronic circuits soiled by solder residues makes it possible, thanks to the properties of the two-phase fluid, to greatly improve the cleaning efficiencies. Indeed, when the two-phase fluid comes into contact with the surface to be cleaned of components and / or electronic circuits, a microbubble release phenomenon on the surface of the components and / or electronic circuits comparable to an ultrasonic cavitation phenomenon occurs. This technique removes even glue residues while avoiding the use of ultrasound and can be used in the field of avionics.

 In an advantageous exemplary embodiment, the injection system is such that the pressure at the nozzles is less than or equal to 5 bars, which makes it possible to obtain efficient cleaning without degrading the components and / or electronic circuits of a very high quality. brittle.

 In order to obtain a homogeneous two-phase fluid, the injector of the mixer injects the gas under pressure into the center of the internal pipe of the fluid mixer. The concentric position of the injector relative to the internal pipe avoids the formation of gas bubble packets in the two-phase fluid.

 The difference between the fluid pressure and the gas pressure inside the fluid mixer is of the order of 1 bar. It has indeed been noted that this pressure difference, the gas being in excess pressure with respect to the liquid, made it possible to produce a very homogeneous two-phase fluid and therefore very effective for cleaning. The pressure difference between the injected gas and the liquid receiving this gas will thus for example be between 0.5 and 2 bars.

Advantageously, the cleaning device comprises a tank of overflow to recover the liquid from the first tank. Said liquid which thus flows into the overflow tank is freed of heavy residues remaining at the bottom of the first tank.

 A suction of liquid inside the overflow tank is advantageously carried out by means of a hydraulic device which connects the overflow tank to the fluid mixer. The latter is then through one of these inputs supplied with liquid already rid of the largest washing residues.

 In order to further protect the fluid mixer from cleaning residues from the overflow vessel, the mixer is advantageously placed downstream of a filter.

 According to one embodiment of the invention, the fluid mixer has a Y-shape facilitating mixing between the gas and the liquid therein. This shape thus allows the creation of microbubbles of gas in the liquid from the overflow tank. In addition, the fluid mixer is advantageously placed upstream of the first tank to facilitate the integration of the mixer within the cleaning device.

 An embodiment of the present invention provides that the means for the nozzles to scan the surface of the components and / or electronic circuits to be cleaned includes means for vertically moving the support means. It may also be provided, possibly in addition to this embodiment, to achieve effective cleaning, that these means for the nozzles to perform the scanning of the surface of the components and / or electronic circuits to be cleaned include means for horizontally moving the nozzles. A preferred embodiment provides the combination of component support movements and / or electronic circuits and nozzles to greatly increase cleaning efficiency. It is then possible to more easily remove the residues on electronic boards and / or components.

In order to reduce the cleaning time but also to preserve the components and / or the electronic circuits to be cleaned of any mechanical stresses created by the projection of a fluid, an advantageous embodiment of the invention further provides that the system injection of a two-phase fluid on the components and / or the electronic circuits to be cleaned comprises two networks of nozzles connected to each other and placed on both sides of the components and / or electronic circuits thus allowing simultaneous cleaning of the two faces of the components and / or electronic circuits .

 Advantageously, depending on the thickness of the components and / or electronic circuits to be cleaned, the distance between said components and / or electronic circuits to clean networks of nozzles is adjustable.

 In a preferred embodiment, the fluid mixer comprises a conical narrowing making it possible to homogenize the distribution of gas bubbles in the fluid. Thus, the two-phase fluid does not have groups or packets of gas bubbles.

 Advantageously, the pressurized gas injected into the second inlet of the fluid mixer is a neutral gas. Thus, it is possible to clean components and or electronic circuits using very easily oxidizable materials such as copper.

 In an exemplary embodiment, the diameter of the internal pipe of the fluid mixer has a diameter of between 15 and 25 mm.

 For its part, the injector of the mixer has an internal diameter of less than 4 mm. Thus, with a relatively small diameter of the injector, it is easier to produce a homogeneous two-phase fluid and to control the characteristic parameters of the two-phase fluid.

 Other features and advantages of the invention will become apparent on reading the description which follows. This is purely illustrative and should be read in conjunction with the accompanying drawing in which:

 - Figure 1 is a block diagram of the device of the invention, and

FIG. 2 is a diagrammatic view on an enlarged scale of part of the device of FIG. 1.

 Figure 1 shows a device 1 comprising a first tank 2, a second tank called overflow tank 4, both of generally parallelepipedal shapes and adapted to contain a liquid.

Support means 8 disposed inside the first tank 2 maintain components and / or electronic circuits 6 to be cleaned immersed in the liquid contained therein. Said components and / or electronic circuits 6 to be cleaned are, for example, substrates based on silicon that can be flexible or chip assemblies based on semiconductor. It can also be electronic cards or screen printing stencils.

 The first tank 2, also called cleaning tank, consists of metal walls made of stainless steel. It comprises inter alia a first vertical vertical wall 21, a lower horizontal bottom 22 and an inner vertical wall 23, said overflow wall with an upper end edge 231 at a height less than that of an upper extreme edge 21 1 of the wall external vertical 21. The inner vertical wall 23 is designed such that the liquid contained in the first tank 2 overflows above the upper end edge 231 to flow into the overflow tank 4 adjacent to the first tank 2.

 The overflow tank 4 is also made of stainless steel metal walls. It comprises inter alia a first vertical vertical wall 42, a horizontal bottom 41 and a second vertical wall which corresponds to the upper part of the inner vertical wall 23 of the first tank 2. In addition, the two tanks are open upwards and the lower horizontal bottom 22 of the first tank 2 is at an altitude lower than the altitude of the horizontal bottom 41 of the overflow tank 4.

 The components and / or the electronic circuits 6 to be cleaned, as shown in FIG. 1, are placed parallel to the vertical vertical wall 21 of the first tank 2 so that they can not come into contact with the lower horizontal bottom 22 of the first tank 2 so as not to disturb the flow of the liquid in said first tank 2. The components and / or the electronic circuits 6 to be cleaned are maintained by the support means 8. These may be a hook system or arm allowing the total immersion of the components and / or electronic circuits 6 to be cleaned in the first tank 2. In addition, the support means 8 can perform a vertical movement (represented by a double arrow in Figure 1) controlled by a suitable control device not shown in Figure 1.

 The device 1 also comprises two hydraulic devices for the circulation of the liquid contained in the two tanks.

A first hydraulic device 12 is associated with the first tank 2. It allows the flow of liquid in the first tank 2 with a suction mouth 121 placed at the bottom of the first tank 2 and a return by an end 122 of the first hydraulic device 12 preferably placed at the top of the vertical vertical wall 21 of the first tank 2, thus allowing the reinjection of the liquid into the first tank 2.

 This first hydraulic device 12 allows the recovery, filtering and injection of the liquid contained in the first tank 2. It comprises for this purpose a valve V1, a pump P1 and a filter F1.

 The valve V1 can be controlled electrically or manually and allows, among other things, during potential incidents to isolate the first tank 2.

 The filter F1 is disposed within the first hydraulic device 12 and is placed for example downstream of the valve V1, to ensure filtering and thereby elimination of cleaning residues of the liquid coming from the first tank 2.

 The pump P1 may be a finned pump or magnetic drive for example and is used for the circulation of the liquid in the first hydraulic device 12.

 A manually or electrically controlled valve V5 is positioned here downstream of the pump P1 to allow the liquid contained in the first tank 2 to be drained into a recovery tank (not shown in FIG. 1), for example using the pump. P1. This valve V5 is mounted on a bypass of the first hydraulic device 12.

 A second hydraulic device 14 comprises a valve V2, a pump P2, a filter F2 and a mixer 16. This second hydraulic device 14 makes it possible, among other things, to suck the liquid into the overflow tank 4 and reinject it into the first tank 2 To do this, a suction mouth 142 is placed so that the suction of the liquid preferably occurs at the bottom of the wall 42 of the overflow tank 4. The return of the liquid is made through a fluid injection system placed in the first tank 2.

 The valve V2, placed on the second hydraulic device 14, can be manually controlled or electrically controlled type for example solenoid valve. This valve V2 allows during an incident potential to isolate the overflow tank 4 for safety reasons.

The liquid contained in the overflow tank 4 is sucked by means of the pump P2, placed here downstream of the valve V2. The filter F2 placed downstream of the pump P2 allows the filtering, that is to say the elimination of cleaning residues of the liquid coming from the overflow tank 4, these residues coming, among others, from the components and / or circuits 6 electronics to clean ..

 The mixer 16 is placed downstream of the filter F2 on the second hydraulic device 14 and is placed upstream of the first tank 2. It has a first inlet 161 adapted to receive a liquid under pressure from the filter F2 powered by the pump P2 in the second hydraulic device 14, a second inlet 162 adapted to receive a gas under pressure and an outlet 163. FIG. 2 is a schematic view on an enlarged scale of the mixer 16.

 All the numerical values given here are given for purely illustrative and non-limiting purposes.

 The first input 161 is coupled to the output 163 by means of an internal pipe of the mixer 16. The diameter of the internal pipe is for example of the order of 16 mm (1 mm = 0.001 m) to a tapered narrowing 164 to change from a pipe diameter of 16 mm (the side of the first inlet 161) to a pipe diameter of 13 mm (the output side 163) (Figure 2).

 The second inlet 162 is connected to the outside of the mixer 16 to a source of pressurized gas. In the mixer 16, the second inlet 162 is connected to an injector for injecting said gas into the internal pipe. The internal diameter of the injector is for example of the order of 2 mm with an outer diameter of about 4 mm. The mixer 16 thus has a shape of Y.

In an advantageous embodiment, the injector is positioned in the center of the internal pipe of the mixer 16, that is to say concentrically with respect to the internal pipe. In addition, the injector penetrates sufficiently into the internal pipe and its end in the inner pipe is close to the conical narrowing 164 of the inner pipe so that the injection of pressurized gas at the center of the internal pipe allows the creation of a two-phase fluid. Due to this conical narrowing 164 the two-phase fluid is accelerated which homogenizes the distribution of gas bubbles. The gas injected into the second inlet 162 may be a neutral gas, for example nitrogen, which makes it possible to clean bare or highly oxidizable copper parts, for example power modules used for energy management in vehicles. electric. Also, the injected gas may be a protective or reducing gas.

The pressure of the liquid injected into the first inlet 161 is of the order of 3 to 5 bar (1 bar = 10 ⁵ Pascals) with a flow rate of 20 liters / min. The pressure of the gas injected into the second inlet 162 is greater than 0.5 to 2 bar, preferably of the order of 1 bar, above the pressure of the liquid and has a flow rate of the order of 10 liters / min. . Advantageously, the flow rates and the pressures of the inputs of the mixer 16 are adjustable.

 The flow rate and the pressure within the second hydraulic device 14 as well as at the second inlet 162 of the mixer 16 are sufficient to meet the cleaning requirements of the components and / or the electronic circuits 6 to be cleaned.

 The fluid injection system comprises two networks of nozzles 1001 and 1003 immersed in the first tank 2. These two networks of nozzles 1001 and 1003 have nozzles 10 placed so that the streams coming from these nozzles 10 are jets of liquid laminar cylindrical and arrive perpendicular to the surface of the components and / or electronic circuits 6 to clean (see Figure 1).

 Said nozzle networks 1001 and 1003 consist of at least one line comprising at least one nozzle 10 and at least one column comprising at least one nozzle 10. The number of nozzles 10, that is to say the number of lines and columns, the nozzle networks 1001 and 1003 can be modified according to the size of the components and / or the electronic circuits 6 to be cleaned.

In addition, in order to preserve the components and / or the electronic circuits 6 to be cleaned of any mechanical stresses created by the spraying of liquid on its two opposite faces, the nozzle networks 1001 and 1003 are placed parallel to the components and / or the electronic circuits. 6 to be cleaned on both sides (see Figure 1). In order to protect fragile electronic components and / or circuits 6 such as soft Kapton semiconductors the distance separating the components and / or the electronic circuits 6 to be cleaned from the nozzle is of the order of 2 to 5 cm. The network of nozzles 1003 is supplied with two-phase fluid from the hydraulic device 14 by means of a hydraulic supply device 1002 connecting the first network of nozzles 1001 to the second network of nozzles 1003. The pressure of the two-phase fluid jet Nozzle level 10 is preferably less than 5 bar. Although relatively low, this pressure allows efficient cleaning of the components or cards to be cleaned while ensuring not to damage the cleaned objects.

 The hydraulic feed device 1002 is preferably situated at the bottom of the first tank 2 without however touching its bottom horizontal bottom 22 so as not to hinder the circulation of the liquid in the first tank 2.

 In addition, the first network of nozzles 1001 and the second network of nozzles 1003 can, with the aid of a scanning device not shown in FIG. 1, carry out a movement perpendicular to the plane of FIG. This movement thus makes it possible to sweep, using the fluid jets, the faces of the components and / or the electronic circuits 6 to be cleaned using the two networks of nozzles.

 This scanning device can also be coupled to the movement of the support means 8. The combined movements then favor the elimination of the residues placed under integrated circuits. In addition, the removal of residues placed in via holes is also improved using this technique.

 In addition, the distance between each network of nozzles and the components and / or the electronic circuits 6 to be cleaned is determined in such a way that the efficiency of the two-phase fluid jets is maximum: this can be for example of the order from 5 to 10 cm.

In another exemplary embodiment, a pressure regulating device (not shown in the figures), using for example pressure sensors, is used to control the pressure of the liquid as well as that of the gas. In order to improve the performances as well as the reproducibility of the cleanings, it is also possible to use a device for regulating the temperature of the liquid, for example using a temperature sensor. The gas may for example be at room temperature. However, a temperature control of the gas can also be considered. Thus, it is possible to perfectly control the characteristics of the two-phase fluid.

 Effective cleaning of electronic boards, and more particularly electronic boards for avionics applications, is now possible through a device as described above. Indeed, the use of a diphasic fluid jet instead of an ultrasonic generator allows the device to be effective during cleaning without damaging or damaging electronic components, even those containing a quartz.

 Moreover, since the efficiency of the diphasic jet is independent of the nature of the materials, for example glue or solder cream, the cleaning of screen printing masks is optimized by such a device. It has been noticed that the presence of microbubbles in the fluid injected by the nozzles on the components and / or the electronic circuits to be cleaned allowed a very high cleaning efficiency even against products such as glue deemed to be impossible to be eliminated by cleaning.

 It will be appreciated that the invention is not limited by the nature and shape of the vessel (s). Also, the embodiment of the device shown in Figure 1 is only a non-limiting example. The materials constituting the tanks may be of a different nature than that stated in the description. Any variant technically feasible embodiment within the scope of the skilled person may be preferred to the embodiments described. Thus, the number of filters on the hydraulic lines or the type of pumps is not limited to the examples given here for purely illustrative purposes.

 The above description has been given for illustrative purposes only and is not limiting of the scope of the invention.

Claims

1. Specific device (1) for cleaning components and / or electronic circuits (6), comprising:  a first tank (2) containing a liquid,  - support means (8) for immersing the components and / or the electronic circuit (6) in the first tank (2), a fluid injection system comprising nozzles (10) for projecting fluid jets onto the components and / or the electronic circuit (6) to be cleaned,  means enabling the jets of fluid coming from the nozzles (10) to sweep the surface of the components and / or the electronic circuit (6) to be cleaned,  characterized in that it further comprises a fluid mixer (16) having a first inlet (161) adapted to receive a pressurized liquid, a second inlet (162) adapted to receive pressurized gas, an outlet (163) designed to supply two-phase fluid to the injection system, the first inlet (161) being coupled to the outlet (163) by means of an internal pipe, the second inlet (162) being supplied with pressurized gas and connected an injector for injecting said gas into the internal pipe. 2. Device according to claim 1, characterized in that the injection system is such that the pressure at the nozzles (10) is less than or equal to 5 bars. 3. Device according to one of claims 1 or 2, characterized in that the injector injects the gas under pressure in the center of the internal pipe of the mixer (16) of fluids. 4. Device according to one of claims 1 to 3, characterized in that the difference between the pressure of the fluid and the pressure of the gas inside the mixer (16) fluids is of the order of 1 bar. 5. Device according to one of claims 1 to 4, characterized in that the cleaning device comprises an overflow tank (4). 6. Device according to claim 5, characterized in that a hydraulic device (14) connects the overflow tank (4) to the fluid mixer (16). 7. Device according to one of claims 1 to 6, characterized in that the mixer (16) of fluids is placed downstream of a filter (F2). 8. Device according to one of claims 1 to 7, characterized in that the mixer (16) fluids has a Y shape. 9. Device according to one of claims 1 to 8, characterized in that the mixer (16) of fluids is placed upstream of the first vessel (2). 10. Device according to one of claims 1 to 9, characterized in that the means allowing the nozzles (10) to scan the surface of the components and / or the electronic circuit (6) comprise means for vertically moving the support means (8). 1 1. Device according to one of claims 1 to 10, characterized in that the fluid injection system comprises means for horizontally moving the nozzles (10). 12. Device according to one of claims 1 to 1 1, characterized in that the fluid injection system comprises two networks of nozzles (1001, 1003) interconnected and placed on both sides of the components and / or circuits electronic (6) to clean. 13. Device according to one of claims 1 to 12, characterized in that the distance between the components and / or the electronic circuit (6) of the nozzles (10) is adjustable. 14. Device according to one of claims 1 to 1 3, characterized in that the internal pipe of the fluid mixer (16) comprises a conical narrowing (164). 15. Device according to one of claims 1 to 14, characterized in that the pressurized gas injected into the second inlet (162) of the mixer (16) of fluids is a neutral gas. 16. Device according to one of claims 1 to 1 5, characterized in that the internal pipe of the mixer (16) of fluids has a diameter of between 15 and 25 mm. 17. Device according to one of claims 1 to 16, characterized in that the injector of the mixer (16) has an internal diameter of less than 4mm.