Recovery of printed circuit boards using swelling agents

Abstract

Methods and systems for recycling printed circuit boards (PCBs). The printed circuit board is exposed to a swelling agent that swells and decomposes an epoxy matrix of the printed circuit board into particles. The particles of the epoxy resin are then separated from the printed circuit board, leaving their reinforcing fibers and metal-containing components. These remaining components are separated from each other and recovered using suitable processes, respectively. Epoxy particles are also restored and can be reduced to monomers for the synthesis of new epoxy resins. The swelling agent includes formic acid as an active ingredient.

Description

Technical Field

[0001] The present invention relates generally to the recycling of composite materials and, more particularly, to the use of a swelling agent that decomposes the epoxy portion of the composite material to facilitate recovery of component materials from printed circuit boards. Background Art

[0002] Consumer electronics such as televisions, computers, and smartphones are becoming increasingly common worldwide, with the average person in most developed countries owning multiple devices. Due to the rapid development of technology in this field, these devices often become obsolete within a relatively short period of time. Therefore, consumer electronics devices are constantly being replaced. This constant replacement cycle generates a significant and increasing amount of electronic waste (e-waste). Printed circuit boards (PCBs) are a major component of this e-waste because they are used in most (if not all) electronic devices manufactured today. PCBs are typically designed to work only in their respective electronic devices and are typically not actually used outside of the electronic devices in which they were initially installed.

[0003] A printed circuit board (PCB) comprises a laminate structure having alternating conductive and insulating layers. Each conductive layer comprises a pattern of conductive traces configured to connect electrical components attached to the PCB in a predefined manner and has a copper layer from which the traces are formed. The insulating layer is typically formed from an epoxy matrix of a cross-linked polyepoxide embedded with reinforcing glass fibers. Although PCBs can have any number of layers, a common PCB configuration known as a "quad-layer board" comprises three insulating layers alternating with four (two outer and two inner) conductive layers. The epoxy matrix binds the PCB's glass fibers together and provides a durable substrate for mounting electrical components. However, this durability also makes it difficult to recycle the materials used to make the PCBs once the electronic device is discarded.

[0004] Conventional attempts to recycle printed circuit boards include mechanical, chemical, and thermal methods. Mechanical methods involve grinding the printed circuit board into small fragments and then separating these fragments into different material streams. However, grinding is only effective at releasing the substrate from the metal-containing portion, often produces toxic gases and dust, and does not result in a high recovery rate of the most valuable components (e.g., precious metals). Chemical methods often produce large amounts of waste that must be disposed of as hazardous waste, potentially creating greater environmental problems than they solve. Thermal methods involve thermal decomposition of the printed circuit boards at high temperatures. However, the pyrolysis treatment of the printed circuit boards produces hazardous chemicals due to the thermal degradation of the epoxy resin and the volatilization of the metal, and consumes a large amount of energy. Due to the shortcomings of the known methods of recycling printed circuit boards, the printed circuit boards are often simply discarded.

[0005] Therefore, there is a need for improved methods and systems for recycling printed circuit boards. Summary of the Invention

[0006] In one aspect of the present invention, a method for treating a printed circuit board comprising an epoxy-based composite material is disclosed. The method comprises exposing the printed circuit board to a swelling agent comprising an effective amount of formic acid. The printed circuit board is exposed to the swelling agent until the epoxy resin swells sufficiently to decompose into swollen epoxy particles. The swollen epoxy particles are then separated from the remainder of the printed circuit board.

[0007] In an embodiment of the method, separating the epoxy particles from the remainder of the printed circuit board can include vibrating the printed circuit board. For example, the printed circuit board can be vibrated near a screen configured to allow the particles of swollen epoxy to fall and retain at least a portion of the remainder of the printed circuit board.

[0008] In another embodiment of the method, at least a portion of the swollen epoxy particles may be suspended in a swelling agent, and separating the swollen epoxy particles from the remainder of the printed circuit board may include filtering the particles from the swelling agent.

[0009] In another embodiment of the method, the method may further include comminuting the printed circuit board into a plurality of fragments. Comminuting the printed circuit board into the plurality of fragments may include, for example, one or more of cutting, grinding, or crushing the printed circuit board. When comminuting occurs prior to exposure to the swelling agent, the printed circuit board may be exposed to the swelling agent by immersing the plurality of fragments in the swelling agent.

[0010] In another embodiment of the method, the method may further include removing the swelling agent, washing the printed circuit board, and drying the printed circuit board after the epoxy resin decomposes. Removing the swelling agent may include draining the swelling agent from a processing chamber containing the printed circuit board, filtering the swelling agent, and returning the swelling agent to a swelling agent tank for supplying the swelling agent to the processing chamber.

[0011] In another embodiment of the method, exposing the printed circuit board to the swelling agent may include one or more of heating the swelling agent, pressurizing the swelling agent, and agitating the swelling agent. The swelling agent may also include one or more of a solvent, a surfactant, and a complexing agent.

[0012] In another embodiment of the method, the method may further include extracting the glass fibers from the remaining portion of the printed circuit board. Extracting the glass fibers may include, for example, inserting a multi-pronged tool into the remaining portion of the printed circuit board and rotating the tool.

[0013] In another embodiment of the method, the method may further include extracting metal from the remaining portion of the printed circuit board. The extracted metal may include a base metal, and extracting the base metal from the remaining portion of the printed circuit board may include exposing the printed circuit board to a general acid and extracting the base metal from the general acid. The general acid may include one or more of hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid.

[0014] In another embodiment of the method, the metal extracted from the remaining portion of the printed circuit board may include a precious metal, and extracting the precious metal may include exposing the printed circuit board to a precious metal solution and extracting the precious metal from the precious metal solution. The precious metal solution may include one of aqua regia or a cyanide salt solution.

[0015] In another embodiment of the method, extracting the metal from the remaining portion of the printed circuit board may include exposing the printed circuit board to an eddy current separator configured to separate the first metal from the second metal.

[0016] In another embodiment of the method, extracting the metal from the remaining portion of the printed circuit board may include extracting the metal from the swelling agent.For example, the metal may be extracted from the swelling agent after separating the swollen epoxy particles from the swelling agent, preferably by filtering.

[0017] In another embodiment of the method, the swelling agent may include formic acid at a concentration of at least 20% by volume.

[0018] In another embodiment of the method, the epoxy-based composite material may include an amine-cured epoxy resin.

[0019] In another aspect of the present invention, a system for processing a printed circuit board according to any of the above methods is disclosed.

[0020] The above summary presents a simplified overview of some embodiments of the present invention to provide a basic understanding of some aspects of the invention discussed herein. This summary is not intended to provide an extensive overview of the invention, nor is it intended to identify any key or critical elements, or to delineate the scope of the invention. The sole purpose of this summary is to present some concepts in a simplified form as an introduction to the detailed description presented below. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate various embodiments of the invention and, together with the general description of the invention given above and the detailed description of the embodiments given below, serve to explain embodiments of the invention.

[0022] Figure 1 is a flow chart depicting an exemplary process for recycling printed circuit boards.

[0023] Figure 2 Is used to execute Figure 1 A schematic diagram of an exemplary system for performing at least a portion of a process.

[0024] Figure 3 Is used to execute Figure 1 A schematic diagram of another exemplary system for at least a portion of a process.

[0025] It should be understood that the drawings are not necessarily drawn to scale and may present somewhat simplified representations of various features illustrating the basic principles of the invention. Specific design features of the operational sequences disclosed herein, including, for example, the specific dimensions, orientations, positions, and shapes of the various illustrated components, may be determined in part by the specific intended application and use environment. Certain features of the illustrated embodiments may have been enlarged or distorted relative to other features for ease of visualization and clarity of understanding. DETAILED DESCRIPTION

[0026] Embodiments of the present invention relate to methods and systems for recycling printed circuit boards (PCBs). The PCB is exposed to a swelling agent that causes the epoxy matrix of the PCB to swell. Theoretically (but not exclusively), swelling occurs when the swelling agent diffuses into the epoxy resin, thereby increasing the volume of the epoxy matrix. As the epoxy resin swells, the mechanical stresses generated cause the epoxy resin to decompose into epoxy particles. The epoxy particles can then be separated from the reinforcing fibers (e.g., glass fibers) and other components of the PCB, and the separated components can be recycled. This includes the epoxy resin, reinforcing fibers, copper, and any number of other metals used in the manufacture of PCBs. The swelling agent includes formic acid as the active ingredient that causes the epoxy resin to swell. Advantageously, because the formic acid is not consumed in any significant amount by the decomposition process, the swelling agent can be easily recycled for processing additional PCBs.

[0027] Epoxy-based composites preferably include amine-cured epoxy resins, as printed circuit boards with amine-cured epoxy-based composites typically exhibit rapid swelling. Examples of amine-cured epoxy systems are Olin Airstone 760 and Hexion RIMR 035C impregnated epoxy resins. Such epoxy systems allow for disassembly by swelling in a swelling agent comprising formic acid under relatively mild conditions. Swelling agents containing at least 50 wt% formic acid are generally found to be effective at ambient temperature and pressure. Swelling agents containing at least 20 wt% formic acid may be effective at elevated temperature, pressure, and / or time. Increased temperature, pressure, and concentration of formic acid generally increase the rate of swelling.

[0028] Figure 1An exemplary process 10 for recycling printed circuit boards according to an embodiment of the present invention is illustrated. In block 12, the process 10 comminutes the printed circuit boards by cutting, grinding, crushing or otherwise breaking the printed circuit boards into fragments. The resulting fragments can be in the form of strips, pieces (e.g., squares) or particles of the printed circuit boards. These fragments can have one or more dimensions (e.g., length, width, or both) that are less than a predetermined length (e.g., less than 50 mm, preferably between 5 mm and 20 mm, and more preferably about 10 mm). The size of the fragments can be selected so that they are small enough to allow the epoxy matrix to be rapidly decomposed by the swelling agent, but large enough to allow their non-epoxy components (e.g., reinforcing fibers and metal-containing components) to be easily separated from the particles of the decomposed epoxy resin, as described in more detail below.

[0029] In an alternative embodiment of the present invention, the shredding step may be skipped. The shredding step may be skipped, for example, if the printed circuit boards being recycled are small, the components of the printed circuit boards are inherently such that they would be easier to sort if the boards were kept intact, or to reduce the complexity of the recycling process.

[0030] At block 14, process 10 exposes a printed circuit board or fragment thereof (hereinafter collectively referred to as a printed circuit board) to a swelling agent. Exposing the printed circuit board to the swelling agent may include applying the swelling agent such that the surface of the circuit board is wetted. For example, wetting may be achieved by placing the printed circuit board in a processing chamber and supplying the chamber with a sufficient amount of swelling agent to submerge the printed circuit board. The swelling agent may also be applied by dispersing or spraying droplets of the swelling agent onto the printed circuit board. Application of the swelling agent in this manner may be continuous or intermittent, with the period between applications being sufficiently short to prevent the wetted surface of the printed circuit board from drying out.

[0031] The swelling agent is configured to cause swelling of the epoxy portion of the printed circuit board. To this end, the swelling agent comprises formic acid. The swelling agent may comprise, for example, an aqueous solution of formic acid having a concentration of at least 20%, more preferably at least 50%, by mass. In some embodiments, the swelling agent may be provided as a 100% concentration of formic acid. Swelling agents with higher concentrations of formic acid may cause the epoxy resin to swell at a faster rate, thereby reducing the time it takes to decompose the epoxy resin.

[0032] The effective amount of formic acid in the swelling agent can vary significantly depending on the conditions under which the epoxy matrix is ​​exposed to the swelling agent. A swelling agent is considered to have an effective amount of formic acid if the concentration of formic acid is sufficient to cause at least 50% of the epoxy matrix to decompose under a selected set of exposure conditions. Exposure conditions that affect the rate of epoxy matrix decomposition can include the size, shape, and type of epoxy matrix being decomposed, as well as the duration, temperature, pressure, and agitation associated with exposure to the swelling agent.

[0033] For example, for the same sample exposed to a swelling agent at 20°C and one atmosphere of pressure for 24 hours without agitation, an effective amount of formic acid may be approximately 75% by volume. In contrast, for the same sample exposed to a swelling agent at the same temperature and pressure for 62 hours without agitation, an effective amount of formic acid may be only approximately 20% by volume. Because the decomposition rate for a given epoxy matrix is ​​generally proportional to the exposure conditions, and these conditions are easily replicated, an effective amount of formic acid for any given set of exposure conditions can be readily determined without undue experimentation.

[0034] In addition to formic acid, the swelling agent may include components such as other organic or inorganic acids, solvents, dissolving salts, surfactants, and complexing agents. Exemplary organic acids that may be added to the swelling agent include trifluoroacetic acid, trichloroacetic acid, methanesulfonic acid, trifluoromethanesulfonic acid, performic acid, acetic acid, propionic acid, lactic acid, and oxalic acid, as well as anhydrides of any of these acids. Exemplary inorganic acids that may be added include hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, boric acid, and hydrobromic acid.

[0035] Exemplary solvents that can be added to the swelling agent include alcohols such as methanol, ethanol, propanol, isopropanol, butanol, tert-butanol, and / or amyl alcohol. In principle, any alcohol that is soluble in the swelling agent can be added. When an alcohol is used as an additional component of the swelling agent, potential esterification of formic acid may occur in some cases because the swelling agent includes formic acid.

[0036] Other solvents that can be added to the swelling agent include tetrahydrofuran (THF), dimethylformamide (DMF), N-Methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), dichloromethane, chloroform, acetone, acetonitrile, chlorobenzene, diethyl ether, dioxane, ethylene glycol, polyethylene glycol (PEG), glycerol, hexamethylphosphoramide (HMPA), nitromethane, pyridine, trimethylamine, toluene, xylene, benzene, dimethylacetamide (DMAc), dimethoxyethane (DME), diglyme, and dichloroethane. The swelling agent including the solvent can be a single-phase or two-phase system. The single-phase system can also include an emulsifier to stabilize the single-phase system.

[0037] Dissolving salts that can be added to the swelling agent include NaCl, KCl, CsCl, NaHCO, KHCO, CsHCO, NaCO, KCO, CsCO, any salt comprising a quaternary ammonium cation, and any salt comprising a tetrafluoroborate anion or a hexafluorophosphate anion. Including a salt in the swelling agent can alter the solubility of certain materials in the swelling agent. For example, for a swelling agent comprising aqueous formic acid, the addition of a salt can alter the hydrophobic effect of the swelling agent. Adding a salt to the swelling agent can also reduce the risk of decomposition of components other than the epoxy resin, thereby preventing components such as reinforcing fibers and metal-containing elements from breaking down into small fragments that are difficult to separate from the epoxy particles.

[0038] Exemplary surfactants that can be included in the swelling agent include anionic and nonionic surfactants such as sulfates, sulfonates, gluconates, cocamide, ethoxylates, and alkoxylates. Adding a surfactant may be advantageous where the swelling agent is an aqueous solution, and the printed circuit board is fully or partially coated with a hydrophobic coating material, or includes one or more inner layers having a hydrophobic coating. Soap and other emulsifiers may also be included in the swelling agent.

[0039] The type and amount of any additional components added to the swelling agent can be selected based on the material being recovered from the printed circuit board. For example, the additional components can be selected to prevent materials other than the epoxy from being dissolved or decomposed by the swelling agent, such as by adjusting the pH of the swelling agent.

[0040] The complexing agent may facilitate the dissolution of one or more metals into the swelling agent, thereby facilitating the recovery of the dissolved metals from the swelling agent.

[0041] The swelling agent can be provided at ambient temperature (e.g., 20-25° C.) or at an elevated temperature (e.g., 25-100° C.). Heating the swelling agent to an elevated temperature can accelerate the swelling process at the expense of increased energy consumption and evaporation of the swelling agent. In particular, the swelling agent can be heated to 50-95° C. to accelerate the swelling process. When an elevated temperature is used, the swelling agent can be maintained at an elevated temperature throughout the swelling process, or the swelling agent can be gradually cooled as the swelling process is about to end. The swelling agent can also be agitated, for example, by circulating the swelling agent, introducing acoustic energy (e.g., ultrasonic energy) into the swelling agent, shaking or rotating the processing chamber, bubbling air through the swelling agent, etc. Agitation of the swelling agent can promote the penetration of the swelling agent into the epoxy resin and / or release swollen epoxy particles from the printed circuit board.

[0042] Exposing the printed circuit board to the swelling agent at atmospheric pressure has the advantage of not requiring the process chamber to be airtight or structurally reinforced to withstand the pressure. For example, the unpressurized process chamber can be an open or otherwise unsealed container. In alternative embodiments, the printed circuit board can be exposed to the swelling agent under pressure (e.g., between one and three atmospheres). Exposing the printed circuit board to the swelling agent under pressure can accelerate the diffusion of the swelling agent into the epoxy matrix and can also allow for higher temperatures (e.g., 100-200° C.) without boiling the swelling agent. The elevated pressure can be generated, for example, by placing the printed circuit board and the swelling agent into a sealed process chamber and then increasing the temperature in the process chamber until the desired temperature and pressure are reached.

[0043] Heating, agitation, and pressurization of the swelling agent can be used independently or in combination to control the rate of the swelling process. The rate of the swelling process can be controlled to reduce the amount of time it takes to decompose the epoxy resin. The rate of the swelling process can also be controlled to adjust the size of the epoxy particles that the epoxy resin decomposes into. Agitation of the swelling agent can be kept low or avoided entirely to keep the printed circuit board relatively intact, or provided at a relatively high level to separate the epoxy particles from the printed circuit board by suspending them in the swelling agent. In the event that the epoxy particles are suspended in the swelling agent, they can be recovered by filtering or centrifuging the swelling agent for recycling.

[0044] The amount of time that a printed circuit board is exposed to a swelling agent to achieve complete decomposition of the epoxy matrix can vary widely depending on the exposure conditions. A printed circuit board passively immersed in a swelling agent having a relatively low concentration (e.g., less than 20%) of formic acid at ambient temperature and pressure may require a relatively long time (e.g., 144 hours or longer) to completely decompose. Increasing the concentration, temperature, pressure, or level of agitation can significantly reduce this time, for example, to less than one hour. The exposure time may also depend on the properties of the printed circuit board, such as the type of epoxy matrix, the degree of crosslinking of the epoxy matrix, and the size and shape of the printed circuit board or its fragments.

[0045] At block 16, process 10 can determine whether the epoxy matrix of the printed circuit board has sufficiently decomposed to allow the epoxy resin to separate from the remainder of the printed circuit board. The level of epoxy decomposition can be determined visually, based on the amount of time and the known decomposition rate, by measuring the turbidity of the swelling agent in the processing chamber, or using any other suitable means. If the epoxy resin has not sufficiently decomposed (the "no" branch of decision block 16), process 10 can continue exposing the printed circuit board to the swelling agent. If the epoxy resin has sufficiently decomposed (the "yes" branch of decision block 16), process 10 can proceed to block 18.

[0046] In block 18, process 10 may remove the swelling agent from the printed circuit board or the remainder thereof. Removal of the swelling agent may include one or more of draining the swelling agent from the processing chamber, flushing the processing chamber with a cleaning agent, and drying the printed circuit board (e.g., by circulating air through the chamber). The cleaning agent may include, for example, water and may also include a surfactant, such as a non-foaming detergent.

[0047] Once the swelling agent has been removed from the printed circuit board, process 10 may proceed to block 20 and separate the epoxy from the remaining components of the printed circuit board. In the event that the epoxy separates from the printed circuit board upon exposure to the swelling agent, or by a subsequent cleaning / rinsing step, the process may skip block 20 and proceed directly to block 22.

[0048] At block 20, process 10 may separate the decomposed epoxy resin from the remainder of the printed circuit board. Separating the decomposed epoxy resin may include vibrating, deforming, or otherwise agitating the printed circuit board. The printed circuit board may be agitated, for example, over a screen configured to capture reinforcing fibers and electrical components of the printed circuit board and allow particles of epoxy resin to fall out. Compressed air may also be used to separate the epoxy particles from other components of the printed circuit board, for example by blowing the epoxy resin particles away from the printed circuit board.

[0049] As mentioned above, the epoxy particles can also be separated using a wet process that suspends the particles and removes them from the rest of the PCB. This step can be performed as a separate step or simultaneously with the removal of the swelling agent, which carries the epoxy particles into the slurry. The swelling agent can be removed from the processing chamber through a filter with a relatively large pore size to allow the epoxy particles to pass through along with the swelling agent to obtain a slurry while preserving the other components of the PCB.

[0050] A subsequent cleaning phase in which a cleaning agent is flushed through the processing chamber can also be used to separate the epoxy particles from the remaining components of the printed circuit board. The cleaning agent can include a surfactant, such as an anionic surfactant and / or an amphiphilic surfactant, such as a quaternary ammonium surfactant. The surfactant can reduce surface tension, thereby increasing the wettability of the cleaning agent and, therefore, increasing its effectiveness in separating the epoxy particles from the remaining components of the printed circuit board. In any case, once released, the epoxy resin particles can be captured and subjected to further processing, such as reduction to a monomer (e.g., bisphenol A (BPA)) that can be used to produce new epoxy resin.

[0051] Separating the epoxy particles from the other components of the printed circuit board may also include mechanically removing the epoxy particles, for example, by scraping, combing, or any other suitable mechanical action. The mechanical removal may be performed prior to cleaning or treatment. In alternative embodiments, the cleaning or rinsing process may be performed after or simultaneously with the mechanical removal of the epoxy particles from the other components of the printed circuit board.

[0052] Any slurry or suspension of epoxy particles obtained in the above manner can be added to any slurry or suspension of epoxy particles obtained during a previous or subsequent step. The combined suspension / slurry can then be further processed, for example, by filtration, centrifugation, or any other suitable means, to extract the epoxy particles. The filtered swelling agent can be kept separate from the cleaning and rinsing fluids so that it can be recycled to process additional printed circuit boards. As part of this recycling process, the concentration of formic acid in the swelling agent can be adjusted. For example, because high concentrations of formic acid can absorb moisture from the air and other sources and can also decompose into water and carbon monoxide, additional formic acid can be added to the swelling agent to maintain the concentration at a desired level.

[0053] In frame 22, reinforcing fibers (e.g., glass fibers) can be separated from the remainder of the printed circuit board based on their substantially different physical properties (e.g., shape, size, electrical conductivity, magnetic permeability, and density). For example, a carding process similar to a cotton gin can be used to pull out reinforcing fibers from the remaining assembly by inserting a multi-pronged tool into the reinforcing fibers and rotating the tool to temporarily entangle the reinforcing fibers on the fork and allowing the reinforcing fibers to be pulled out from the remaining assembly. For example, separation can be further enhanced by using a vibrating separator, an air cushion table, or any other suitable device. The reinforcing fibers can then be recovered, for example, by melting in the case of glass fibers or by directly cleaning and reusing the reinforcing fibers.

[0054] After the reinforced fiber portion of the printed circuit has been separated, the remaining portion of the printed circuit board can be primarily composed of metal-containing components, such as copper traces, solder, gold contacts, etc. Therefore, process 10 can proceed to block 24 and extract base metals from this remaining portion of the printed circuit board. Base metals can be extracted using electronic, mechanical, or chemical means based on differences in their physical or chemical properties. For example, a magnetic separator can be used to separate iron and other magnetic metals. The remaining metal can then be passed through an eddy current separator to separate light metals (e.g., aluminum) from heavier metals (e.g., copper) based on differences in their density and electrical conductivity.

[0055] Depending on the separation process used, the remaining portion of the printed circuit board may be subjected to a further comminution stage to further reduce and standardize the size of the separated particles. For example, the particles may be sorted by size and passed through one or more electrostatic separators. Chemical separation of the base metals may be performed by selectively exposing the metals to one or more universal acid solutions (e.g., hydrochloric acid, nitric acid, sulfuric acid, or phosphoric acid) configured to react with a specific metal or metal group and dissolve the resulting salt or salts. The universal acid solution may then be drained and stored for subsequent processing to recover the dissolved metal salts.

[0056] In block 26, the process can extract precious metals (e.g., gold and platinum). The precious metals can be extracted chemically, for example, by exposing the remaining portion of the printed circuit board to a precious metal solution consisting of aqua regia or a cyanide salt solution. After the precious metal solution has extracted the precious metals, it can be drained and stored for later processing to recover the precious metals.

[0057] Figure 2 An exemplary system 30 for recycling printed circuit boards is illustrated. System 30 includes a processing chamber 32, a swelling agent source 34, a cleaning agent source 36, a swelling agent recovery tank (recovery tank) 38, a cleaning agent recovery tank 40, and a controller 42. Processing chamber 32 can be operably coupled to swelling agent source 34 and cleaning agent source 36 via respective source pumps 44, 45 and heater 48. Each source pump 44, 45 can be configured to provide a swelling agent or cleaning agent, respectively, in response to a signal from controller 42. Source pumps 44, 45 can also be configured to provide their respective reagents under pressure to processing chamber 32, for example, to support pressurized processing of printed circuit boards. Heater 48 can be selectively activated by controller 42 to heat the swelling agent or cleaning agent as they flow through heater 48 to processing chamber 32.

[0058] The processing chamber 32 may also be operably coupled to the swelling agent recovery tank 38 and the cleaning agent recovery tank 40 via a drain pump 46, a filter 50, and a plurality of valves 52. The drain pump 46 may be configured to draw liquid, such as a swelling agent or a cleaning agent, from the processing chamber 32 in response to a signal from the controller 42. The controller 42 may selectively open and close the valves 52 so that the fluid drawn from the processing chamber flows into the correct reagent recovery tank.

[0059] The controller 42 may include a processor 54, a memory 56, an input / output (I / O) interface 58, and a user interface 60. The processor 54 may include one or more devices that manipulate signals based on operating instructions stored as applications 62 in the memory 56 and executed by the processor 54. The I / O interface 58 may provide a machine interface that operably couples the processor 54 to other devices and systems, such as the pumps 44-46, the heater 48, and the valve 52. The applications 62 may thereby control the system 30. The user interface 60 may be operably coupled to the processor 54 of the controller 42 to allow a user to interact directly with the controller 42. To this end, the user interface 60 may include output devices capable of providing data to the user and input devices capable of accepting input from the user.

[0060] Figure 3 Another exemplary system 70 for recycling printed circuit boards is shown. System 70 includes a shredding station 72, a swelling station 74, a swelling agent source 76, a filter separator 78, an air separator 80, and an eddy current separator 82. Printed circuit boards 84 can initially be provided to shredding station 72, where they are divided (e.g., cut) into pieces of generally uniform size (e.g., 10 mm square). The printed circuit board pieces can then be provided to swelling station 74, where they are exposed to swelling agent 76.

[0061] The printed circuit board fragments can be exposed to the swelling agent 76 for a known, predetermined period of time to allow the epoxy matrix of the printed circuit board fragments to fully decompose. In alternative embodiments, the amount of time the printed circuit board fragments are exposed to the swelling agent 76 can be controlled based on observation of the state of the fragments or based on sensor data. During at least a portion of the time the printed circuit board fragments are exposed to the swelling agent 76, the swelling agent 76 can be circulated with sufficient force to dislodge decomposed epoxy particles. The dislodged epoxy particles can then be flushed through the swelling agent 76 into a filter separator 78. The filter separator 78 can separate the epoxy particles from the swelling agent 76, allowing the epoxy particles 86 to be recovered for further processing, such as reduction to monomers at an off-site chemical processing facility, and preferably recycling. The filtered swelling agent 76 can be returned to the swelling agent source 76 for reuse.

[0062] After fully removing epoxy resin from printed circuit board, its remaining components (e.g., reinforcing fibers and metal-containing components) can be provided to the separator chamber of air separator 80. Air can circulate through the separator chamber to separate lighter materials (e.g., reinforcing fibers 88)) from heavier materials (e.g., metal-containing components). The amount of air flow required for separation can be blown upwards through the separation chamber. This air flow can be configured to carry lighter components upwards, wherein they are collected in the top portion of the chamber, for example, by a cyclone separator. Meanwhile, air flow may not be enough to support heavier components. Therefore, heavier components may fall downwards and be collected in the bottom portion of the chamber. The collected reinforcing fibers 88 are then recyclable or reused, and the heavier material is provided to eddy current separator 82.

[0063] The eddy current separator 82 may include a belt and a magnetic drum that carry particles of different metals. The magnetic drum can rotate at a high speed (e.g., 4,000 RPM). The belt and the magnetic drum can be configured to provide relative motion between the metal particles and the magnetic drum so that magnetic lines of force pass through the particles. The magnetic lines of force can induce a current in the particles that is proportional to their electrical conductivity. The interaction between the induced current and the magnetic field may affect the trajectory of the particles as they fall from the belt. The resulting trajectory can be different based on the relative conductivity and mass of the particles, so that lighter and more conductive particles (i.e., light metal 90) are collected in one box, and heavier and less conductive particles (i.e., heavy metal 92) are collected in another box. The sorted metal particles can then be further processed using chemicals, electroplating, or other suitable means to recover each type of metal for reuse.

[0064] In general, the routines executed to implement embodiments of the present invention may be referred to herein as "computer program code" or simply "program code." Program code generally includes computer-readable instructions that reside at various times in various memories and storage devices within a computer and, when read and executed by one or more processors within a computer, cause the computer to perform the operations necessary to implement the operations or elements embodying various aspects of embodiments of the present invention.

[0065] In some alternative embodiments, the functions, actions or operations specified in the flowchart, sequence diagram or block diagram can be reordered, processed serially or processed simultaneously according to embodiments of the present invention. In addition, any one of the flowchart, sequence diagram or block diagram can include more or fewer blocks than shown in accordance with embodiments of the present invention. It should also be understood that each block of the block diagram or flowchart or any combination of blocks in the block diagram or flowchart can be implemented by a dedicated hardware-based system configured to perform the specified function or action, or performed by a combination of dedicated hardware and computer instructions.

[0066] While all of the inventions have been illustrated by the description of various embodiments, and while these embodiments have been described in considerable detail, it is not the applicant's intention to restrict or in any way limit the scope of the appended claims to such detail. Other advantages and modifications will be readily apparent to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus and methods, and illustrative examples shown and described. Accordingly, departures may be made from these details without departing from the spirit or scope of the applicant's overall inventive concept.

Claims

1. A method for treating a printed circuit board comprising an epoxy-based composite material, the method comprising: exposing the printed circuit board to a swelling agent until the epoxy resin swells sufficiently to decompose into swollen epoxy particles; as well as separating the swollen epoxy particles from the remainder of the printed circuit board, Wherein, the swelling agent includes an effective amount of formic acid.

2. The method according to claim 1, wherein Separating the swollen epoxy particles from the remainder of the printed circuit board includes vibrating the printed circuit board.

3. The method according to claim 2, wherein: The printed circuit board is vibrated adjacent a screen configured to allow particles of swollen epoxy to fall through and retain at least a portion of a remainder of the printed circuit board.

4. A method according to any one of the preceding claims, wherein At least a portion of the swollen epoxy particles are suspended in the swelling agent, and separating the swollen epoxy particles from a remainder of the printed circuit board includes filtering the particles from the swelling agent.

5. The method according to any one of the preceding claims, further comprising: The printed circuit board is shredded into a plurality of fragments.

6. The method according to claim 5, wherein: Shredding the printed circuit board into a plurality of fragments includes one or more of cutting, grinding, or crushing the printed circuit board.

7. The method according to claim 5 or 6, wherein: Exposing the printed circuit board to the swelling agent includes immersing the plurality of fragments in the swelling agent.

8. The method according to any one of the preceding claims, further comprising: exhausting the swelling agent from a processing chamber containing the printed circuit board; filtering the swelling agent; as well as The swelling agent is returned to a swelling agent tank, which is used to supply the swelling agent to the processing chamber.

9. A method according to any one of the preceding claims, wherein Exposing the printed circuit board to the swelling agent includes one or more of heating the swelling agent, pressurizing the swelling agent, and agitating the swelling agent.

10. A method according to any one of the preceding claims, wherein The swelling agent further comprises one or more of a solvent, a surfactant and a complexing agent.

11. The method according to any one of the preceding claims, further comprising: Glass fibers are extracted from the remaining portion of the printed circuit board.

12. The method according to claim 11, wherein Extracting the glass fiber comprises: inserting a multi-pronged tool into the remaining portion of the printed circuit board; and Rotate the tool.

13. The method according to any one of the preceding claims, further comprising: The metal is extracted from the remainder of the printed circuit board.

14. The method according to claim 13, wherein: The extracted metals include base metals, and extracting the base metals from the remainder of the printed circuit board includes: exposing the printed circuit board to a common acid; and Extracting said base metals from said universal acid, The general acid includes one or more of hydrochloric acid, nitric acid, sulfuric acid and phosphoric acid.

15. The method according to claim 13 or 14, wherein: The extracted metal includes a precious metal, and extracting the precious metal from the remainder of the printed circuit board includes: exposing the printed circuit board to a precious metal solution; and extracting the precious metal from the precious metal solution, The noble metal solution is one of aqua regia and cyanide salt solution.

16. The method according to any one of claims 13 to 15, wherein: Extracting the metal from the remaining portion of the printed circuit board includes: The printed circuit board is exposed to an eddy current separator configured to separate a first metal from a second metal.

17. The method according to any one of claims 13 to 16, wherein: Extracting the metal from the remainder of the printed circuit board includes extracting the metal from the swelling agent.

18. The method according to claim 17, wherein After separating the swollen epoxy particles from the swelling agent, the metal is extracted from the swelling agent.

19. A method according to any one of the preceding claims, wherein The swelling agent comprises formic acid at a concentration of at least 20% by volume.

20. A method according to any one of the preceding claims, wherein The epoxy-based composite material includes an amine-cured epoxy resin.

21. Apparatus for processing a printed circuit board according to any preceding claim.

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