WO2020074541A1

WO2020074541A1 - Using ozone for manganese* oxidation in etching application

Info

Publication number: WO2020074541A1
Application number: PCT/EP2019/077265
Authority: WO
Inventors: Walter UTTINGER; Bruno Heiniger; Laurent DE FRANCESCHI
Original assignee: Degrémont Technologies Ag
Priority date: 2018-10-08
Filing date: 2019-10-08
Publication date: 2020-04-16

Abstract

Method for etching or plating a component, comprising the steps of: - etching or plating a component preliminary placed into an etching or plating tank, with a solution containing at least one transition metal, such as manganese, - prior, simultaneously, or after to the etching or plating of the component, the method comprises the step of: - mixing gas containing ozone with at least a portion of the solution, so as to at least partly oxidize said at least one transition metal.

Description

Using Ozone for manganese^* oxidation in etching application

[0001] The present invention relates to manufacturing processes where a component (typically an electronic component such as a circuit board) is plated or etched. However, the method is not limited in any case to such components.

[0002] In etching processes the use of Chrome (chromium) is forbidden since

September 2017 (Reach regulation). Companies still have exemption of several years until one reliable alternative solution is available onto the market.

[0003] There would be an interest in developing an etching or plating process free of chromium use.

[0004] An object of the present disclosure is to provide a method for etching or plating a component using other compounds than chromium.

[0005] In this aim, an aspect of the invention is a method for etching or plating a component, comprising the steps of:

- etching or plating a component preliminary placed into an etching or plating tank, with a solution containing at least one transition metal, such as manganese,

- prior, simultaneously, or after to the etching or plating of the component, the method comprises the step of:

- mixing a gas containing ozone with at least a portion of the solution, so as to at least partly oxidize said at least one transition metal,

[0006] Species, meaning transition metal, which could be treated with the present method are:

• silver (preferred), manganese (preferred), cobalt, ruthenium, cerium, iron, nickel, rhodium, and vanadium. • silver² ions, Co³⁺, cerium (III) or (IV), iron (II) or (III), manganese (IV) or higher, nickel (II) (II) or (IV), ruthenium (V) (VI) (VII) (VIII), vanadium (IV) or (V).

• cerium (III) sulphate, iron (II) sulphate, manganese (II) sulphate, nickel (II) sulphate.

[0007] The solution is preferably a liquid solution.

[0008] The method according to the above embodiment comprises a step of at least partly oxidizing the transition metal.

[0009] Advantageously, the step of mixing the gas containing ozone with a portion of the solution is performed:

- after a step of pumping or isolating the portion of the solution from the etching or plating tank, and/or ;

- before a step of sending back said at least one portion of solution into the etching or plating tank.

[0010] This step of mixing the gas containing ozone with a portion of the solution is preferably performed on a portion of the liquid solution contained in the etching/plating tank. The portion of the liquid solution is taken or pumped out of the etching/plating tank prior and/or simultaneously and/or after the etching/plating step. Once the portion of the liquid solution is taken or pumped out of the etching/plating tank, an oxidization is carried out by mixing/exposing the portion of the liquid solution with ozone.

[0011] In other words, in parallel to the etching/plating process, the transition metal is continuously pumped (with the portion of solution), oxidized and sent back to the etching/plating tank. The transition metal is regenerated by the oxidization step.

[0012] Preferably, the taking/pumping out of the etching/plating tank might be a continuous step, at least during a predetermined time period, more preferably simultaneously to the etching/plating step. [0013] Preferably, the mixing/exposure of the portion of the liquid solution with ozone might be a continuous step, at least during a predetermined time period, more preferably simultaneously to the etching/plating step.

[0014] Advantageously, the step of mixing the gas containing ozone with a portion of the solution is performed within a venturi, or a mixer.

[0015] Advantageously, the method comprises a step a pumping a portion of the solution into a circuit separate from the etching or plating tank, prior to mixing.

[0016] Preferably, the taking/pumping out of the etching/plating tank and the mixing/exposure of the portion of the liquid solution with ozone are performed through a closed loop treating circuit.

[0017] Advantageously, the method comprises a step of storing into a reactor the portion of solution mixed with the gas containing ozone, for a predetermined amount of time.

[0018] Advantageously, the method comprises a step of collecting an off-gas, during or after the mixing.

[0019] Advantageously, the off-gas is dried, and/or cooled, and/or treated before release to the atmosphere. Drying the off-gas help to protect the downstream equipment, especially if some off-gas is reinjected into the liquid solution / matrix.

[0020] Advantageously, the solution is heated at a temperature comprised in the range of [50°C - 80°C] included, preferably [60°C-70°C] included. Despite the fact that ozone generally breaks down rapidly at such temperatures, the Applicant surprisingly found out that the treatment (oxidization) of the transition metal is efficient in the above range of temperature with ozone.

[0021 ] Advantageously, the method comprises a preliminary step of preparing the liquid solution, with at least:

- said transition metal, and

- sulfuric acid, and/or Methanesulfonic acid. [0022] In particular, the liquid solution / matrix can present pH < 1 , and the Applicant surprisingly found out that the treatment (oxidization) of the transition metal is efficient with ozone in such acidic conditions, despite such conditions usually accelerate breaking down of ozone.

[0023] Advantageously, the method comprises a preliminary step of producing the gas containing ozone, on site, or in a location remote from the etching or plating site.

[0024] Advantageously, the gas containing ozone is produced from oxygen.

[0025] In particular, the present invention relates to using electro-oxidation for Manganese 2 (or Manganese II) conversion into Manganese 3 (or Manganese III).

[0026] The purpose of the present invention is to propose an alternative ozone based solution for Manganese II oxidation into Manganese III. Manganese can be replaced by other specific compounds. The general process is etching on plastic or other material by a dedicated liquid solution / matrix.

[0027] This liquid solution / matrix could be mainly composed of sulfuric and Methanesulfonic acids including different metals or other components such as Manganese, Silver, iron, metals in general and other specific compounds.

[0028] Such a liquid solution / matrix main characteristics are that it is very corrosive and hazardous for operator and equipment with:

• pH < 1

• temperature of 60 to 70 °C

[0029] An objective of the present disclosure is to provide a dedicated solution for oxidation by ozone which could be as well integrated in an existing process or as a skid-based commercially available solution.

[0030] Regarding the present disclosure, several options and variants are considered. Other features and advantages of the present invention will appear more clearly from the following detailed description of particular non- limitative examples of the invention, illustrated by the appended drawings where:

Figure 1 describes a first embodiment of a general process of compounds oxidation by ozone in the dedicated liquid solution / matrix ;

Figure 2 represents the structure of an example of machine to implement the process.

[0031] In Figure 1 , an ozonized gas is produced from oxygen (in the ozone generator unit) and mixed with the liquid solution / matrix to be treated. The liquid solution / matrix is pumped from the etching process (Combined Filter Effluent tank (CFE tank)/electro-plating by an adapted pump.

[0032] Mixing (in the diffuser/mixer) can be performed through several options (dedicated diffuser) such as Venturi ejector, static mixer or others. The oxido/reduction reaction starts at the mixing point in between the two phases.

[0033] The mixed phase, gas-liquid, is brought to a reactor or reacting unit where oxido-reduction reaction is continuing and ending. Volume of the reactor is sized to fit with the time reaction required at the specific operating conditions. As an example, with a flow rate of about 5m³/h, preferably 3m³/h and more preferably 2m³/h, and a reactor of about less than 80 liters, preferably less than 50 liters, and more preferably of about 25 to 30 liters, the residence time could be less than 5 minutes, preferably less than 3 minutes, and more preferably less than 1 minute, so as treat the transition metal such as Manganese.

[0034] Such short exposure time is sufficient to achieve an efficient oxidization, even at such (high) temperature and under such acidic conditions. This results in a time efficient treatment process, ensuring effective oxidization of the transition metal, before ozone breaks down. [0035] Degassing is done at this stage and the treated liquid solution / matrix goes back to the etching process tank by gravity or additional specific equipment such as pump and buffer tank, as an option.

[0036] It is also foreseen to merge diffusion, mixing and reactor in a variant embodiment of the innovation. On another hand, different diffuser could be combined as for example: Venturi or static mixer and radial diffuser specific equipment.

[0037] According to an aspect, off-gas is collected from the reacting unit at 60 °C to 70 °C, containing partial humidity, and needs to be treated before discharge in the atmosphere. Specific off-gas treatment line is designed taking into consideration safety, environmental and corrosive issues. Several options and variants are foreseen including part or total of the following devices:

• cooling system for off-gas gas cooling · separator

* demister

[0038] According to an aspect, remaining ozone is removed by specific Vent Ozone Destructor using thermal or chemical effect.

[0039] Figure 2 shows an example of Piping and instrumentation diagram or Process and instrumentation diagram to carry out the invention.

Material used:

[0040] Regarding the material used for the solution, it would need to be adapted to the highly corrosive matrix (temperature from 60°C to 70°C ; pH < 1 ). This could be, e.g.: · Special high grade stainless steel (316L, 904 L, Duplex steel, super duplex steel (duplex steel and super duplex steel are stainless steel with metallurgical structure consisting of two phases, austenite (face- centered cubic lattice) and ferrite (body centered cubic lattice) in roughly equal proportions, duplex steel is typically Grade EN 1.4462 (also called 2205), and super duplex steel is typically grade EN 1.4410 )...)

• Fluoropolymers (Polytetrafluoroethylene - PTFE, Polyvinylidene fluoride - PVDF . )

• Coated steel with Fluoropolymers or ceramic or more generally all substances adapted to the matrix.

[0041] Figure 2 represents a sketch of an example of equipment for carrying out the disclosed method.

[0042] A pump 11 generates a flow of liquid solution / matrix M (an etching or plating solution for example) from an etching tank 10, to a reacting unit comprising a first reactor 20 and a second reactor 30 (which may be a degassing tank), an injector 19 being arranged upstream the reacting unit to inject a gas containing ozone into the liquid solution / matrix M.

[0043] In the reacting unit, the compounds contained in the solution are oxidized, and in particular, the solution M contains a transition metal, such as Manganese, and this transition metal is oxidized. As an example Manganese II is then oxidized into Manganese III. Then, a return line transfers the treated liquid solution / matrix M back to the etching tank 10. It has to be noted that speed of liquid solution/matrix in first reactor 20 and/or second reactor 30 is low compared to speed in piping, to achieve an efficient treatment.

[0044] Reverting to the gas containing ozone injected into the solution M, the gas containing ozone is generated by an ozone generator unit OGU, fed with oxygen 02 by an oxygen source S, and supplied with electric current by a current generator, so as to generate ozone via corona discharge. The ozone generator unit OGU is also connected to a heat exchanger HE so as to maintain adequate temperature conditions. [0045] The gas exhausted out of the ozone generator OGU is sent to the injector 19 via an exhaust line 50 and typically contains ozone (0₃) and oxygen (O₂). One can consider a mixture of [5%-20%] ozone (O3) and [95%- 80%] oxygen (0₂) as an example.

[0046] The gas circuit also comprises a sampling branch 60 for measuring an ozone content, and realizing the sampled gas to atmosphere via an ozone destructing device. For setting a reference, the sampling branch 60 is connected to the oxygen source S to receive, in a calibration step, pure oxygen, so as to check the accuracy of sensors.

[0047] The reacting unit (first reactor 20 and second reactor 30) are also connected to an off-gas collect line 40, which comprises a demisting unit DU to remove humidity from the off-gas, and which sends the off-gas to a gas treatment unit GTU for sending to atmosphere, or back to the line for injection into the liquid solution / matrix M by injector 19, based on a measurement of ozone content of the collected off-gas received from the reacting unit.

[0048] The gas treatment unit GTU may typically treat gas to remove ozone and heat. As an example, the gas treatment unit GTU can comprise an ozone destruction unit, a (further) demister unit, a heat exchanger unit.

[0049] It is of course understood that obvious improvements and/or modifications for one skilled in the art may be implemented, still being under the scope of the invention as it is defined by the appended claims. In particular, one can consider measuring working parameters (temperature and/or pH and/or ozone content and/or flow... ) at entry and/or exit of first reactor 20, second reactor 30, demisting unit DU, ozone generating unit OGU... , to adapt the flow speed, residence time in first reactor 20, second reactor 30 to still achieve an efficient treatment.

Claims

CLAI MS

1 . Method for etching or plating a component, comprising the steps of:

- mixing a gas containing ozone with at least a portion of the solution, so as to at least partly oxidize said at least one transition metal,.

2. Method according to the preceding claim, wherein the step of mixing the gas containing ozone with a portion of the solution is performed:

3. Method according to any one of the preceding claims, wherein the step of mixing the gas containing ozone with a portion of the solution is performed within a venturi, or a mixer.

4. Method according to any one of the preceding claims, comprising a step a pumping a portion of the solution into a circuit separate from the etching or plating tank, prior to mixing.

5. Method according to any one of the preceding claims, comprising a step of storing into a reactor the portion of solution mixed with the gas containing ozone, for a predetermined amount of time.

6. Method according to any one of the preceding claims, comprising a step of collecting an off-gas, during of after the mixing.

7. Method according to the preceding claim, wherein the off-gas is dried, and/or cooled, and/or treated before release to the atmosphere.

8. Method according to any one of the preceding claims, wherein the solution is heated at a temperature comprised in the range of [50°C - 80°C] included, preferably [60°C-70°C] included.

9. Method according to any one of the preceding claims, comprising a preliminary step of preparing the solution, with at least:

- said transition metal, and

- sulfuric acid, and/or Methanesulfonic acid.

10. Method according to any one of the preceding claims, comprising a preliminary step of producing the gas containing ozone, on site, or in a location remote from the etching or plating site.

11. Method according to the preceding claim, wherein the gas containing ozone is produced from oxygen.