EP2283171A1

EP2283171A1 - Method for selectively depositing a precious metal on a substrate by the ultrasound ablation of a mask element, and device thereof

Info

Publication number: EP2283171A1
Application number: EP09761646A
Authority: EP
Inventors: Sylvain Rochon; Jean-Yves Hihn; Loïc HALLEZ; Francis Touyeras
Original assignee: Centre National de la Recherche Scientifique CNRS; Universite de Franche-Comte; C&K Components SAS
Current assignee: Centre National de la Recherche Scientifique CNRS; Universite de Franche-Comte; C&K Components SAS
Priority date: 2008-06-12
Filing date: 2009-06-03
Publication date: 2011-02-16
Anticipated expiration: 2029-06-03
Also published as: WO2009150083A1; FR2932497A1; ATE549435T1; FR2932497B1; EP2283171B1

Abstract

The invention relates to a method for selectively depositing a precious metal (32) on a metal substrate (10), the method sequentially comprising: a masking step, consisting of depositing a mask element (16) on one treated surface (12) of the metal substrate (10); a selective ablation step, for the selective ablation of at least one removed portion (17) of the pre-deposited mask element (16) to expose at least one deposition area (18) of said treated surface (12) of the metal substrate (10); a deposition step, for depositing the precious metal (32) on said pre-exposed deposition area (18); and characterized in that the selective ablation step involves the ultrasound wave (22) irradiation of said removed portion (17) of the mask element (16) to destroy said removed portion (17). The invention also relates to an ultrasound device (20) for implementing the selective ablation step.

Description

"Process for selectively depositing a precious metal on a support by ultrasonic ablation of a masking element and its ispositif"

The invention relates to a method for the selective deposition of a precious metal on a metallic support, such as a metallic support strip, by ultrasonic ablation of a masking element.

The invention also relates to a device for implementing a step of the deposition process. The invention relates more particularly to a process for the selective deposition of a precious metal on a metallic support, which process comprises successively:

a masking step consisting in depositing a masking element on a face to be treated of the metallic support in order to cover the face to be treated,

a step of selective ablation of at least one portion to be removed from the previously deposited masking element, which consists in discovering a corresponding deposition zone of said face to be treated of the metallic support, a deposition step of the metal valuable on the deposit area previously discovered.

Numerous processes are known for depositing a precious metal on a metal support, or substrate, in particular processes for depositing a precious metal by electrochemical reaction, such as electroplating.

Electroplating is a process for applying to at least one deposition area of a surface to be treated with a metallic support, a metallic deposition in solution in a liquid by means of a continuous electric current or drawn. The deposit zone thus covered by the precious metal is for example intended to constitute an electrical contact zone. The metal carrier is, for example, in the form of a metallic support strip which consists of a series of components connected to each other.

Such a strip shape allows the continuous metallization of the support strip to be driven, for example, between rotating rollers on a surface treatment line, so as to allow the continuous deposit of the precious metal on the strip of metal. support.

This deposit of precious metal continuously can be realisé notably by depositing methods said "jet", "spot" or "by brushing".

Also known is a process for selectively depositing a precious metal on a metallic support, which consists of depositing the precious metal selectively on at least one predetermined deposition zone of a face to be treated with the metallic support, way to save precious metal.

This type of selective deposition comprises a masking step which consists in depositing a masking element on the face to be treated of the metallic support, the masking step being followed by a selective ablation step.

The selective ablation step consists in removing at least a portion of the previously deposited masking element in order to discover at least one deposition zone of the face to be treated of the metal support. Finally, the selective deposition process comprises a step of depositing the precious metal on the previously discovered deposit zone of the face to be treated of the metallic support.

According to the prior art, this precious metal deposition step is performed by electroplating. The electroplating here makes it possible to deposit an adherent layer of small thickness of the precious metal, ically on the deposition area discovered. EP-B1-1409.772 discloses a method of selective deposition of a precious metal on a metal support, the selective removal step of the masking element is performed by means of a laser. The portion to be removed from the masking element is subjected to a laser beam which destroys the portion to be removed, in order to discover a deposition zone of the face to be treated of the metal support.

Subsequently, the deposit zone thus discovered is covered by the precious metal during a deposition step of the precious metal.

The ablation of the portion to be removed from the masking element by a laser has the disadvantage of heating the metal support, more precisely the deposition area of the support, which may deteriorate the metallic support and oxidize.

To remedy this drawback in particular, the invention proposes a selective deposition process, the ablation step of which does not damage the metal support.

For this purpose, the invention proposes a method of the type described above, characterized in that the selective ablation step consists of irradiating with ultrasonic waves the portion to be removed from the masking element, so as to destroy ire said portion to be removed to discover said corresponding deposition area. According to other features of the invention:

the ultrasonic waves constitute a beam of ultrasonic waves which are focussed so that the ultrasonic waves converge towards the portion to be removed from the masking element, in order to destroy the portion to be removed; the ultrasound ablation step is carried out in an aqueous medium; the method comprises a preliminary step that is carried out before the masking step and that comprises successively:

a degreasing phase of the metallic support, a stripping phase of the metallic support,

a first phase of rinsing of the metallic support, a first phase of activation of the metallic support, a phase of nickel-plating of the metallic support, a second phase of rinsing of the metal support, a first phase of drying the metallic support;

the masking step comprises successively:

a deposition phase of the masking element on the face to be treated of the metallic support,

a ground phase idification of the masking element; the masking element deposited during the masking step is capable of being polymerized, and in that the masking element is soiled by polymerization during the soil phase; masking;

the masking element deposited during the masking step is an element of the type of a resin, a paint or an ink;

the masking element which is deposited during the masking step is deposited on the face to be treated of the metallic support by an electrochemical deposition process; the step of depositing the precious metal successively comprises:

a second phase of activation of the metallic support, a phase of deposition of the precious metal on the deposition zone, and a third phase of rinsing of the metal support;

the deposition phase of the precious metal on the deposition zone discovered on the face to be treated of the metallic support is made by electroplating; the method comprises a step of el imination of the masking element remaining at the end of the ablation step, the said elimination step being carried out following the step of depositing the precious metal; the process comprises a finishing step which comprises successively:

a fourth phase of rinsing of the metallic support, a third phase of activation of the metallic support, a phase of tinning of the metal support, a fifth phase of rinsing of the metal support,

a second phase of drying the metallic support. The invention also proposes a device for implementing the method, characterized in that it comprises:

a tank containing an aqueous substance, in which the metallic support is able to be immersed in displacement in the said aqueous substance,

an ultrasonic wave emitting means which is movably mounted, with respect to the metallic support, on a structural element of the device so that the emitting means is able to occupy at least one ablation position in which the ultrasonic waves irradiate the portion to be removed from the masking element,

means for focusing said ultrasonic waves towards a point of convergence so as to irradiate said portion to be removed from the masking element.

According to another feature of the device, the device comprises motorized means for moving the ultrasound wave transmission means to its ablation position, and in that the device comprises means for controlling said motorized means. .

Other features and advantages of the invention, as well as design details and real isation will appear on reading the detailed description that will be learned for the understanding of which reference will be made to the accompanying drawings in which:

- Figure 1 is a schematic perspective view, which illustrates a section of a metal support strip; FIG. 2 is a schematic perspective view, which illustrates the support strip of FIG. 1 after a step of masking the support strip by a masking element, according to a selective deposition process according to the invention;

FIG. 3 is a schematic perspective view, which illustrates the support strip of FIG. 2 after a step of ablation of a portion to be removed from the masking element, according to the method;

FIG. 4 is a schematic perspective view, which illustrates the support strip of FIG. 3 after a step of deposition of a precious metal on deposition zones of the support strip discovered during the step of ablation, according to the method;

FIG. 5 is a schematic perspective view, which illustrates the support band of FIG. 4 after a step of removing the masking element remaining after the step of depositing the precious metal, according to the method;

FIG. 6 is a diagrammatic view illustrating an ultrasound device for implementing the ablation step, comprising means for emitting ultrasonic waves, a transducer of which is mounted mobile in 3 degrees of freedom;

FIG. 7 is a schematic view illustrating the ultrasonic wave emitting means of FIG. 6 in an ablation position of the masking element of the support strip during the ablation step; ; FIG. 8 is a schematic detail view, which illustrates the irradiation of the masking element by the ultrasonic wave emission means during the ablation step. The longitudinal, vertical and transverse orientations according to the L, V, T trihedron represented in the figures will be used without limitation.

We will also adopt, and the terms upper and lower with reference to the vertical direction of the reference V, L, T.

In addition, identical, similar or analogous elements of the invention will be designated by the same reference numerals.

FIG. 1 shows a section of a metal support strip 10, one of which is to be treated by a process for the selective deposition of a precious metal.

FIG. 1 represents here only a portion of the metal support strip 10. Indeed, the support strip 10, in its entirety, extends in a longitudinal direction, so that the support strip 10 is able to be moved during the process, for example between rotating rollers (not shown), on a surface treatment line (not shown).

The support strip 10 is constituted by a series of elements 14 to be treated which are connected together to form the support strip 10.

The elements 14 to be treated are, for example, electrical contact elements, two of which are shown in FIG. 1, which are for example made by cutting and deformation of the support strip 10.

The selective deposition process comprises a preliminary step of preparing the face to be treated 12 of the section of the support strip 10.

The preliminary preparation step comprises a degreasing phase of the face to be treated 12 of the support strip 10, by example by immersion of the section of the support strip 1 0 in a trichlorethylene bath.

In addition, the preliminary preparation step comprises a stripping phase of the face to be treated 1 2 of the section of the support strip 1 0, which is carried out following the degreasing phase.

Also, the preliminary preparation step comprises a first rinsing phase, which is su ivie by a first activation phase. The first activation phase consists in activating the face to be treated 1 2 of the section of the support band 1 0, for example by immersing the support 1 0 in a sulfuric acid bath.

The first activation phase is followed by a nickel phase of the preliminary step. The nickel-plating phase consists in depositing a nickel-protective layer on the face to be treated 1 2 of the section of the support strip 1 0, in order to protect the face to be treated 12 against corrosion and to prevent migration. and the diffusion of the metallic compounds of the face to be treated 1 2. The preliminary stage of preparation of the method comprises a second phase of rinsing the face to be treated 1 2 of the section of the support strip 1 0, that i is Realized after the nickeling phase.

Finally, the preliminary step of the method comprises a first phase of drying the face to be treated 1 2 of the section of the support strip 10.

The preliminary step of preparing the process is followed by a masking step.

The masking step comprises a deposition phase that consists of depositing a masking element 1 6, or coating, on the face to be treated 1 2 of the section of the support strip 10, in order to cover the face to be treated 12 as shown in Figure 2. The masking element 16 is here a resin 16 which is deposited on the face to be treated 12 by electrochemical deposition, so that the resin 16 covers the face to be treated 12 of the section of the support strip 10 homogeneously and with a constant thickness.

Resin 16 is here a resin which is capable of being polymerized and which is constituted based on acrylate and epoxide.

The masking step comprises a solidification phase which is carried out following the deposition phase, and which consists in solidifying the resin 16 previously deposited on the section of the support strip 10.

For this purpose, the masking resin 16 successively undergoes a polymerization operation, for example by being passed through an oven, or by cataphoresis, and then a crosslinking operation, here by irradiating the resin 16 with ultraviolet rays.

The resin 16, after the solidification phase, must respond to mechanical stresses that are related to the driving of the support strip 10 during the process on the surface treatment line.

Thus, the resin 16 deposited on the support strip 10 must be particularly resistant to torsion, bending, compression and shearing.

In addition, the resin 16 is resistant to the products that may be used during the various subsequent phases of the process, in particular to the activation, rinsing and electroplating phases of the precious metal, which is described in FIG. following the description.

The deposition process comprises a selective ablation step which is performed after the masking step described above.

The selective ablation step consists in irradiating with ultrasonic waves 22 a plurality of portions to be removed 17 (of which two are shown in Figure 2) of the resin 1 6 masking previously deposited, so as to remove by destruction the portions to remove 1 7, as shown in Figure 8. Once removed, each portion to remove 17 of the resin

1 6 masking allows to discover a corresponding deposition area 1 8 (of which two are shown in Figure 3) of the face to be treated 1 2 of the section of the support strip 10, as shown in Figure 3. As the illustrates Figures 6 to 8, ultrasonic waves

22 constitute a beam of ultrasonic waves 22 of high intensity that propagate along a first longitudinal axis A long.

The ultrasonic waves 22 are focalized so as to converge towards a convergence point January 9, so that the ultrasonic wave beam 22 is of a substantially conical shape with a decreasing section towards the portion to be removed 1 7 from the element Masking 16.

The support band 10 is driven in displacement during the ablation step, according to a direction which is generally orthogonal to the first axis A of propagation of the ultrasonic waves, here in a long longitudinal direction, by training means. (not shown)

During the displacement of the support strip 10, the elements 14 to be treated which constitute the support strip 1 0 are arranged successively in line with the ultrasonic wave beam 22, so that the portion to be removed 1 7 each element 14 to be treated is arranged on the point of convergence 1 9, and so that the portion to be removed 1 7 so targeted is destroyed by the ultrasonic waves 22. This type of ultrasonic wave 22 is known in the English terminology " High Intensity Focused Ultrasound.

The ultrasonic ablation step of the selective deposition process is here carried out in an aqueous medium, whereby the section of the support strip 10, more precisely the deposition zone 18, does little or no heat when it is irradiated by the ultrasonic waves 22.

The deposition process comprises a step of depositing a precious metal 32, which is performed following the ablation step.

The deposition step comprises a second activation phase which consists in activating the deposition zones 18 of the face to be treated 12 of the section of the support band 10, for example by immersing the support 10 in a sulfuric acid bath. .

The deposition step comprises a deposition phase which is performed following the second activation phase and which consists in depositing a precious metal 32 on the deposition zones 18 of the face to be treated 12 of the section of the strip of deposition. 10. The deposition zones 18 correspond to the deposition zones which are discovered following the ablation of the portions to be removed 17 from the masking resin 16, during the ablation step.

The precious metal 32 is, for example, gold, silver, tin mixed with lead, pure tin, or nickel.

The precious metal 32 is deposited electroplating here, which makes it possible to deposit an adherent layer of small thickness of the precious metal 32 only on the deposition zones 18 discovered, as can be seen in FIG. 4. Without limitation, the precious metal 32 can be deposited by conventional methods of depositing the type d it "by jet", "by spot", "by brushing" or by any other type of deposition process for depositing a layer of the precious metal 32.

Finally, the deposition step comprises a third rinsing phase of the section of the support strip 10.

Finally, the selective deposition process includes a finishing step that is performed after the deposition step. The finishing step comprises a third activation phase of the support band 1 0.

The activation phase is followed by a tinning phase of the zones of deposits 1 8 of the face to be treated 1 2 of the section of the support strip 10, the zones of deposits 1 8 being previously covered with the precious metal 32.

Tinning is provided for the subsequent welding of a component (not shown) to each tinned deposition zone 18. Finally, the finishing step comprises a fourth rinsing phase of the portion of the support strip 1 0 which is followed by a second drying phase of the support strip 1 0.

The invention also relates to a device 20 for implementing the ablation step of the method, which is shown in FIGS. 6 to 8.

The device 20 has a tray 28 which is open vertically upward and contains an aqueous substance 30, such as water.

The tray 28 has a first vertical wall 26a which delimits a first light 32a, and a second vertical wall 26b opposite which delimits a second light 32b.

The first lumen 32a and the second lumen 32b are arranged opposite and each is in the form of a transverse slot. As illustrated in FIG. 7, the section of the support strip 1 0 extends longitudinally in the tray 28, from the first light 32a to the second light 32b, so that the section of the light strip support 10 is immersed in the aqueous substance 30. The support strip 10 is able to be driven longitudinally through the tray 28.

The aqueous substance 30 flows continuously from the first light 32a and the second light 32b, up to a container (not shown) which is arranged below the tray

28.

The aqueous substance which is contained in the container is filtered and re-injected into the tank 28 by means of a pumping device (not shown).

The device 20 comprises an arcuate structural element 34 which is curved upwards and is fixed to the tray 28, so that the structural element 34 extends transversely above the tray 28. In addition, according to FIG. 6, the structural element 34 delimits a glissière 36 which extends transversely facing the aqueous substance 30 of the tank 28.

The device 20 comprises a transducer 24 which constitutes a means for the em ission of the ultrasonic waves 22 and which is movably mounted on the structural element 34.

In addition, the transducer 24 is arranged so that it is immersed in the aqueous substance 30 of the tank 28.

For this purpose, the transducer 24 is carried by a carriage 38 which is movably mounted on the structural element 34. The carriage 38 comprises an upper attachment finger 40, a first upper portion 40a of which is received in a sliding direction in the glissier 36 complementary to the structural element 34 and a second lower section 40b is reliied on a first median branch 42a of a U-shaped arm 42. Complementarily, the device 20 comprises a first motorized drive means (not shown) that allows the driving of the upper portion 40a of the hooking finger 40 into the associated link 36 of the structural element 34. The gripping finger 40 extends here along the first propagation axis of the ultrasonic waves 22, substantially orthogonal to the structural element 34. In addition, the first upper portion 40a and the second lower portion 40b of the latching finger 40 are slidably mounted one inside the other along the first axis A, in the manner of a jack, so that the axial length the hooking finger 40 is adjustable.

Complementarily, the device 20 comprises a second motorized drive means (not shown) which allows the sliding drive of the first upper portion 40a relative to the second lower portion 40b of the hooking finger 40, along the first axis A.

The U-shaped arm 42 has a second limb 42b and a third limb 42c which extend parallel from the first medial branch 42a and which are each connected to the transducer 24, so that the transducer 24 is pivotally mounted between the second limb 42b and the third leg 42c of the arm 42 about a second pivot axis B.

The second pivot axis B is here orthogonal to the first propagation axis of the ultrasonic waves 22.

Complementarily, the device 20 comprises a third motorized drive means (not shown) which allows the transducer 24 to be pivotally driven about the second pivot axis B.

The first, second and third motorized drive means are controlled by first control means (not shown).

Thus, the first axis A for propagation of the ultrasonic waves 22 is inclinable with respect to the upper surface 12 of the support strip 10, by moving the latching finger 40 in the slideway 36 of the structural element 34 and by pivoting of the transducer 24 around the second pivot axis B.

Advantageously, when the first axis A of propagation of the ultrasonic waves 22 is inclined relative to the face of 12, the ultrasonic waves 22 which are reflected by the face to be treated 1 2 do not irradiate, or little, the transducer 24.

In addition, the distance between the transducer 24 and the support strip 10 is adjustable by varying the axial length of the gripping finger 40, so as to be able to precisely arrange the point of convergence 19 of the ultrasonic waves 22 on the portion to be removed 1 7 from the support strip 1 0.

Thus, the transducer 24 is able to occupy a plurality of ablation positions in each of which the ultrasonic waves 22 irradiate the portion to be removed 1 7 from the masking element 1 6 of the support band 10.

In addition, the transducer 24 is able to scan the portion to be removed 1 7 of the masking element 1 6 of the support band 1 0.

The transducer 24 is associated with second control means (not shown) of the transducer 24, for adjusting the power and the frequency of the ultrasonic waves 22, and for adjusting the irradiation time of the portions to be removed. of the resin 1 6 masking by the ultrasonic waves 22.

The ultrasonic waves 22 are emitted by the transducer 24 pulsed in the manner of a pulsed signal.

The puissance of ultrasonic waves 22 is here between d ix and one thousand watts, the frequency is between one and d ix mega Hertz and irradiation time is between one hundred microseconds to a few minutes.

Also, the focal distance between the point of convergence 1 9 and the transducer 24 is here between d ix and two hundred millimeters. Finally, the device 20 comprises a focalization means

(not shown) ultrasonic waves 22 towards the convergence point 19. According to an alternative embodiment of the deposition process, illustrated in FIG. 5, the deposition process comprises an additional step of removing the remaining masking element 16, which is produced as a result of the metal deposition step. valuable 32 and before the finishing step.

The further removal step is to remove the masking member 16 that has not been removed during the ablation step, as shown in FIG. 5.

The elimination step is followed by a fifth rinsing phase of the section of the support strip 10.

According to another variant embodiment not shown, the masking element 16 is in the form of an adhesive film which is bonded to the face to be treated 12 of the support strip 10. According to another embodiment, the resin 16 as a masking element 16 may be an ink, such as polyamide ink, or a paint, such as acrylic paint, or a polyurethane-based resin 16.

According to this variant, the polymerization of the resin 16 during the solidification phase of the masking step is carried out by evaporation of a solvent which is contained in the resin 16.

Also, the resin 16, whether a paint, an ink, a resin 16 based on polyurethane or an acrylate-based epoxy resin, can be deposited on the face to be treated 12 of the support strip 10 to the during the deposition step of the masking step, for example by spray spraying, electrochemical deposition or by vacuum deposition.

Similarly, the resin 16 may be deposited on the face to be treated 12 of the support strip 10 during the deposition phase of the masking step by means of a brush or a roller.

Claims

1. A method of selectively depositing a metal (32) on a metal support (10), which process comprises successively:

a masking step consisting in depositing a masking element (16) on a face to be treated (12) of the metal support (10) in order to cover said face to be treated (12),

a step of selective ablation of at least one portion to be removed (17) from the previously deposited masking element (16), which consists in discovering a corresponding deposition zone (18) of said face to be treated (12) the metal support (10),

a deposition step of the metal (32) on said previously discovered deposition zone (18), characterized in that the selective ablation step consists of irradiating with ultrasonic waves (22) said portion to be removed;

(17) of the masking element (16), so as to destroy said portion to be removed (17) to discover said corresponding deposition area (18).

2. Method according to claim 1, characterized in that the ultrasonic waves (22) constitute a beam of ultrasonic waves which are focused so that the ultrasonic waves (22) converge towards the portion to be removed (17) of the element masking device (16) to destroy said portion to be removed (17).

3. Method according to any of the preceding claims, characterized in that the ultrasonic ablation step is performed in an aqueous medium (30).

4. Method according to any one of the preceding claims, characterized in that it comprises a preliminary step that i realizes before the masking step and that i comprises successively:

a degreasing phase of the metal support (10),

a stripping phase of the metal support (10), a first phase of rinsing the metallic support (10),

a first phase of activation of the metal support (10), a phase of nickel-plating of the metal support (1 0),

a second rinsing phase of the metallic support (10),

a first phase of drying the metallic support (10).

5. Method according to claim 1, characterized in that the masking step comprises successively:

a deposition phase of the masking element (1 6) on the face to be treated (1 2) of the metal support (10),

- A ground phase idification of the masking element (16).

6. Method according to claim 5, characterized in that the masking element (1 6) deposited during the masking step is capable of being polymerized, and in that the masking element (1 6) is soil idi fi ed by polymerization during the soil phase id ification of the masking step.

7. Method according to any one of claims 1, 5 and 6, characterized in that the masking element (1 6) deposited during the masking step is a member of the type of a resin, d 'a painting or an ink.

8. Process according to any one of claims 1, 5,

6 and 7 characterized in that the masking element (16) which is deposited during the masking step is deposited on the face to be treated (1 2) of the metal support (1 0) by a method of electrochemical deposit.

9. Process according to claim 1, characterized in that the step of depositing the metal (32) comprises successively:

a second phase of activation of the metallic support (10), a metal deposition phase (32) on said deposition zone (18), and

a third phase of rinsing the metal support (10).

10. Method according to the preceding claim, characterized in that said metal deposition phase (32) on the deposition area (18) discovered from the face to be treated (17) of the metal support (10) is made by electroplating.

1 1. Process according to Claim 1, characterized in that it comprises a step of eliminating the masking element

(16) remaining following the ablation step, said removing step being performed following the metal deposition step (32).

12. Method according to claim 1, characterized in that it comprises a finishing step which comprises successively:

a fourth phase of rinsing the metal support (10),

a third phase of activation of the metal support (1 0),

a tinning phase of the metal support (10),

a fifth phase of rinsing the metal support (10),

a second phase of drying the metal support (1 0).

13. Device (20) for implementing the method according to any one of the preceding claims, characterized in that it comprises:

a tank (28) containing an aqueous substance (30), in which the metal support (10) is able to be immersed in displacement in said aqueous substance (30), an ultrasonic wave transmission means (22) which is movably mounted relative to the metal support (10) on a structural element of the device (20) so that the emitting means (24) is adapted to occupy at least one ablation position in which the ultrasonic waves (22) irradiate said portion to be removed (17) from the masking element (16),

means for focusing said ultrasonic waves (22) towards a point of convergence (1 9) so as to irradiate said portion to be removed (1 7) from the masking element (1 6).

14. Device (20) according to the preceding revendication ication, characterized in that it comprises motorized means for moving the transmission means (24) of ultrasonic waves (22) to its ablation position, and in that the device (20) comprises means for controlling said motorized means.