CONDUCTOR BOARD WITH CUREABLE MARKS

Abstract

A printed circuit board (PCB) for an electronic device assembly, such as a solid-state drive (SSD), includes at least one solder mask formed from a curable dielectric material and / or conductor tracks formed from a curable conductive material. Thus, the solder mask(s) and / or conductor tracks can be selectively cured. The curable dielectric material can flow when heated to a repair temperature. The curable conductive material can flow when a repair voltage is applied. Electronic device assemblies and methods for repairing the solder masks and conductor tracks of the printed circuit boards of the electronic device assemblies are also disclosed.

Description

BACKGROUND A printed circuit board (PCB) of a data storage device typically includes a solder mask on each major surface of the board. The solder mask facilitates the electrical coupling of a storage device (e.g., a NAND flash memory), a controller, and other components to the PCB. While initially effective, conventional solder masks are prone to physical damage (e.g., scratches, cracks, etc.) that can compromise the electronic connections between the PCB and the storage device. Any physical damage reduces the performance of the storage device, shortens its potential lifespan, and ultimately leads to its failure. Printed circuit boards (PCBs) also include conductive traces that transmit electrical signals between devices mounted on the PCBs or otherwise electrically coupled to them. PCB traces are typically made of copper, which has low resistivity and high conductivity. Over time and with repeated use, copper traces can become damaged, affecting the performance and reliability of the PCB and any electronic device it incorporates, potentially leading to data errors, communication failures, and device malfunctions. Accordingly, it would be advantageous for a printed circuit board to include solder masks and / or traces that can be repaired. Furthermore, it would be advantageous to have a printed circuit board with solder masks and / or traces that can be repaired quickly and cost-effectively. SUMMARY A printed circuit board (PCB) of this disclosure includes features that can heal themselves when damaged. Such a PCB may be designed for use with one or more storage devices (e.g., one or more NAND devices, etc.) and / or as part of a solid-state drive (SSD). In some examples, the PCB feature that can heal itself may have a configuration that allows for selective healing or repair. In other examples, the PCB may be part of an electronic device (e.g., an SSD, etc.) that may be programmed to heal the feature. In some examples, the printed circuit board may include a solder mask that can be selectively healed if damaged. The solder mask may comprise a dielectric material that can heal upon exposure to a sufficient temperature. This dielectric material may be referred to as the "healable dielectric material." The temperature that allows the healable dielectric material to heal may be referred to as the "repair temperature." The healable dielectric material may comprise one or more dynamic covalent polymers (DCPs), Diels-Alder adducts (DAs), and / or metal-ligand coordination polymers (e.g., a zinc-ligand coordination polymer, etc.). In some examples, the healable dielectric material may comprise at least one dynamic covalent polymer, at least one DA adduct, and at least one metal-ligand coordination polymer. The repair temperature of such a curable dielectric material may be approximately equal to or higher than the operating temperature of the electronic device to which the printed circuit board (PCB) belongs, while remaining low enough to prevent thermal damage to the PCB and / or other components and features of the electronic device assembly to which the PCB belongs. For example, the repair temperature may be lower than the reflow temperature of the solder of an electronic device assembly to which the PCB belongs. The curable dielectric material may have a repair temperature of approximately 100 °C or higher and approximately 180 °C or lower. In some examples, the repair temperature of the curable dielectric material may be in a range of approximately 100 °C to approximately 150 °C or in a range of approximately 100 °C to approximately 130 °C. A method for repairing damage to the solder mask of such a printed circuit board (PCB) may optionally include the detection of damage to the solder mask. The method may also include the application of heat to the damage and subsequent cooling of the solder mask material. The heat may be applied specifically to a damaged area of ​​the solder mask. Alternatively, the heat may be applied generally to the entirety of the solder mask, as well as to the PCB and any electronic device assembly to which the PCB belongs (e.g., an SSD, etc.). The solder mask may be heated to a repair temperature that allows the solder mask material to heal without damaging the PCB supporting the solder mask or any other components or features of an electronic device assembly to which the PCB and solder mask belong.For example, the solder mask can be heated to a temperature in a range of approximately 100 °C to approximately 130 °C, a range of approximately 100 °C to approximately 150 °C, a temperature up to approximately 180 °C, etc. When heat is applied to the solder mask, hydrogen bonds in the curable dielectric material of the solder mask can break, covalent bonds of a DCP in the curable dielectric material of the solder mask can break, bonds formed by DA reactions in the curable dielectric material of the solder mask can break, and / or metal-ligand bonds in the curable dielectric material of the solder mask can detach. When the curable dielectric material of the solder mask cools, the hydrogen bonds in the curable dielectric material of the solder mask can be restored, the bonds formed by DA reactions in the curable dielectric material of the solder mask can be restored, and / or metal-ligand bonds in the curable dielectric material of the solder mask can re-establish themselves, thereby repairing the damage to the solder mask. In some examples, the printed circuit board (PCB) may include conductive traces, which can be more simply referred to as "tracks," that can be selectively or automatically healed if broken or otherwise damaged. The conductive traces of such a PCB may comprise a polyimide with sufficient silver and copper nanoparticles distributed throughout the polyimide to enable the trace to transmit an electrical signal at an operating voltage (e.g., approximately 3.3 V to approximately 5 V, etc.) of an electronic device (e.g., an SSD, etc.) to which the PCB belongs. If such a trace is broken or otherwise damaged, it can be repaired by applying a repair voltage (e.g., approximately 5 V to approximately 10 V, etc.) that exceeds the operating voltage. Therefore, such a material may be described as a "healable conductive material." The printed circuit board (PCB) can be part of an electronic device assembly (e.g., an SSD, etc.) that includes two or more semiconductor devices, such as a storage device (e.g., a NAND flash memory, etc.) and a controller, which communicate with each other via traces on the PCB. Each of the semiconductor devices can apply the repair voltage to a damaged trace. If one of the semiconductor devices is a storage device, it can include a multiplier circuit that boosts the operating voltage to a repair voltage and selectively applies the repair voltage to a damaged trace. A method for repairing a break or other damage to a trace on a printed circuit board (PCB) may involve identifying each trace with a break or other damage and applying a repair voltage to the trace to repair the break. The repair voltage (e.g., approximately 5 V to approximately 10 V, etc.) may exceed an operating voltage (e.g., approximately 3.3 V to approximately 5 V, etc.) of the electronic device to which the PCB belongs. When the repair voltage is applied to the broken or otherwise damaged trace, the curable conductive material can heal the break or other damage. More specifically, the polymer and the silver and copper nanoparticles of the curable conductive material can flow across the break or other damage. Applying the repair voltage to opposite sides of the break or other damage (e.g., from both ends of the trace, etc.) is possible.This can ensure that the repair is properly carried out across the break or other damage. For example, the repair voltage can be applied from one side by a controller of the electronic device assembly. In examples where the repair voltage can be applied to opposite sides of the break or other damage, the repair voltage can be applied from the other side of the track by a multiplier circuit of a storage device (e.g., a NAND gate, etc.) of the electronic device assembly. Other aspects of the disclosed subject matter, as well as features and advantages of various aspects of the disclosed subject matter, should become obvious to those skilled in the art by considering the following description, the accompanying drawings and the accompanying claims. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 schematically shows a repairable solder mask on a printed circuit board (PCB); Figures 2, 3, 4 to 5 schematically show a process for repairing damage to the repairable solder mask of Figure 1; Figures 6, 7, 8, 9 to 10 schematically show an electronic device assembly with a printed circuit board that includes repairable traces; Figure 6 shows the printed circuit board before a break or other damage to one of its traces; Figure 7 shows the printed circuit board with traces that have been broken or otherwise damaged; Figure 8 shows the application of a repair voltage to a broken or otherwise damaged trace from opposite sides of the break or other damage; Figure 9 shows the application of a repair voltage to another broken or otherwise damaged trace from opposite sides of the break or other damage; and Figure 10 shows the printed circuit board with repaired traces. DETAILED DESCRIPTION In the manufacturing and assembly of SSDs, solder mask damage can have significant economic consequences. Revenue losses due to solder mask damage typically amount to 2 to 5% of manufactured SSDs. Conventional repairs are costly and time-consuming. However, there may be situations where an SSD's solder mask is too severely damaged to be repaired using conventional techniques, and the SSD must be discarded. Thus, the total annual losses from repairing and scrapping SSDs with defective solder masks can be substantial. These significant financial implications underscore the need for improved solutions to effectively address solder mask damage. Conventional methods for improving solder mask durability have included increasing the coating thickness or applying additional protective layers. While these methods are effective to some extent, they can lead to higher manufacturing costs and more complex manufacturing processes, without addressing the repair of minor damage. Other approaches to improving SSD good quantities include manual repair techniques and frequent inspections, both of which are labor-intensive and therefore not cost-effective. Damage to the solder mask can cause problems not only during SSD assembly but also over time, as the solder mask helps protect the printed circuit board (PCB), the storage device(s) on the PCB, and the electrical connections between the storage device(s) and the PCB. Damage to the solder mask can compromise the integrity of the SSD, allow contaminants to come into contact with sensitive components and features, and disrupt the transmission of electrical signals necessary for the SSD to function properly. An SSD's ability to function reliably over extended periods also depends on the integrity of its conductive paths, including the traces on the SSD's circuit board. These traces, typically made of copper, can degrade over time due to a variety of factors, including physical stress, temperature fluctuations, and electrical overload. These and other factors can lead to broken or disconnected traces, resulting in data errors, communication failures, and device malfunctions. State-of-the-art solutions for repairing broken traces, such as manual intervention through resoldering or the use of conductive adhesives, are not feasible in highly integrated systems with complex microcircuits. Furthermore, manual repairs of multiple closely spaced broken traces carry the risk of accidental short circuits or misconnections, potentially leading to device failure. While some systems incorporate redundant paths to prevent single-point failures, the use of redundant paths increases design complexity and necessitates a larger SSD circuit board. With reference to Fig. 1, an example of a printed circuit board (PCB) 10 is shown. The PCB 10 encloses a surface 12 which carries a solder mask 20. The solder mask 20 comprises a material that can be cured, or a curable dielectric material 22. Thus, the solder mask 20 includes a curable solder mask. The curable dielectric material 22 of the solder mask 20 allows for the repair of damage to the solder mask 20 (e.g., scratches on the solder mask 20, microcracks or cracks in the solder mask 20, etc.). The curable dielectric material 22 can include bonds that can be broken upon heating and restored upon cooling. More specifically, the curable dielectric material 22 can comprise a base resin, one or more thermoplastic polymers, and at least one heat-activated reversible polymer (HARP) 24. The HARP 24 can comprise at least one dynamic covalent polymer (DCP), at least one Diels-Alder adduct (DA adduct), and / or at least one metal-ligand coordination polymer (e.g., a zinc-ligand coordination polymer, etc.). The base resin of the curable dielectric material 22 can comprise a material that is durable, electrically insulating, moisture-resistant, heat-resistant, and resistant to etching by soldering flux. Examples of materials suitable for use as the base resin as a solder mask include, but are not limited to, epoxy resins, acrylic resins, polyester resins, and the like. The base resin can be a material commonly used for forming solder masks. The use of such a base resin can ensure that the curable dielectric material 22 can be integrated into existing printed circuit board manufacturing processes and that the solder mask 20 formed from the curable dielectric material 22 is compatible with existing manufacturing processes (e.g., assembly, solder reflow, etc.). In addition to the base resin, the curable dielectric material 22 can include one or more thermoplastic polymers. The one or more thermoplastic polymers can include a polyurethane. Polyurethanes are durable and flexible. The properties of polyurethanes can be tailored by modifying their polyol and isocyanate components. Alternatively or additionally, the one or more thermoplastic polymers can include a polyimide. Polyimides are thermally stable, chemically resistant, and can contribute to the mechanical properties of a solder mask 20 (e.g., strength, resistance, hardness, ductility, brittleness, etc. of the solder mask 20). In addition to hydrogen bonding in the curable dielectric material 22, the HARP(s) 24 (e.g., the DCP(s), DA adduct(s), and / or metal-ligand coordination polymer(s), etc.) of the curable dielectric material 22 can impart further properties (e.g., additional bonding types, etc.) to the curable dielectric material 22, which enable the healing of physical damage to the curable dielectric material 22 and thus the healing of damage to a solder mask 20 formed from the curable dielectric material 22. Hydrogen bonds 26 within the curable dielectric material 22 are non-covalent interactions between molecules with electronegative atoms. Hydrogen bonds 26 in the curable dielectric material 22 can be reversed or broken by heating the curable dielectric material 22. Hydrogen bonds 26 can be restored by allowing the curable dielectric material 22 to cool. A DCP includes covalent bonds 27 that can reverse or break and reform under certain conditions. For example, the application of heat to the curable dielectric material 22 can break the covalent bonds 27 of a DCP, while cooling of the curable dielectric material 22 can form covalent bonds 27 of the DCP. In a DA adduct, a [4+2] cycloaddition reaction, or DA reaction, has taken place between a diene and a dienophile, generating two pi bonds (π bonds) and two sigma bonds (σ bonds) 28 between the diene and the dienophile. The π bonds and σ bonds 28 can be broken by heating the curable dielectric material 22 (i.e., a retro-DA reaction). The π bonds and σ bonds 28 can reform (i.e., a DA reaction) by allowing the curable dielectric material 22 to cool. A metal-ligand coordination polymer incorporates metal-ligand coordination bonds 29 in which a metal ion (e.g., a zinc ion or Zn²⁺, etc.) is coordinated to one or more ligands. Metal-ligand coordination bonds 29 can be broken by heating the curable dielectric material 22. Metal-ligand coordination bonds 29 can reform by cooling the curable dielectric material 22. The breaking of bonds 26, 27, 28, 29 in the repairable dielectric material 22 allows at least some components of the repairable dielectric material 22 to flow back into damaged areas of the solder mask 20. The temperature at which various bonds 26, 27, 28, 29 in the repairable dielectric material 22 can break can be the repair temperature of the repairable dielectric material 22. The repair temperature of the repairable dielectric material 22 can be approximately 180 °C or less. In some examples, the repair temperature of the repairable dielectric material 22 can be in a range of approximately 100 °C to approximately 150 °C or in a range of approximately 100 °C to approximately 130 °C.In some examples, the repair temperature of the curable dielectric material 22 can be an operating temperature of a printed circuit board 10 covered by the solder mask 20, allowing any damage to the solder mask 20 to heal itself during operation of an electronic device comprising the printed circuit board 10 and the solder mask 20. Once the curable dielectric material 22 has flowed back into the damaged areas of the solder mask 20, it can be allowed to cool. As the curable dielectric material 22 cools, the bonds 26, 27, 28, and 29 reform, restoring the integrity of the solder mask 20 formed by the curable dielectric material 22 and completing the repair of the solder mask 20. In addition to the materials described above, the curable dielectric material 22 may contain one or more hardeners. The hardener(s) may react with the resin to define the strength and other properties (e.g., hardness, ductility, brittleness, etc.) of the curable dielectric material 22 and of a solder mask 20 formed from the curable dielectric material 22. The curable dielectric material 22 may also contain one or more additives. Non-restrictive examples of additives include fillers, dyes, ultraviolet absorbers (UV absorbers), and the like. A filler may optimize the mechanical properties, heat resistance, and chemical resistance of the curable dielectric material 22 and of a solder mask 20 formed from the curable dielectric material 22. A dye may define the color of the curable dielectric material 22 and of a solder mask 20 formed from the curable dielectric material 22. A UV absorber may enable the use of UV irradiation and chemical development processes to produce solder masks 20 or other structures from the curable dielectric material 22. In a specific, but not limiting, example, the curable dielectric material 22 can be formulated as follows: Base resin 60% Polyurethane 8% Polyimide(s) 6% Dynamic covalent polymers (DCP) 8% Diels-Alder adduct(s) (DA adduct(s))2% Zinc ligand coordination bonds 2% hydrogen bonds Fillers 15% Additives 3% Dyes 1% Fig. 2, Fig. 3, Fig. 4 to Fig. 5 illustrate a method for repairing damage 23 to a solder mask 20 formed from a curable dielectric material 22, is illustrated and described. In Fig. 2, a solder mask 20 may be damaged. Some examples of damage 23 to a solder mask 20 include scratches, microcracks, and cracks. The damage 23 may occur after the solder mask 20 has been formed on a printed circuit board 10, during the assembly of the printed circuit board 10 and the solder mask 20 with other components (e.g., controllers; storage devices such as NAND devices, etc.), during the handling of an assembly that includes the printed circuit board 10 and the solder mask 20 (e.g., during the manufacture of an electronic device, etc.), or during the use of an electronic device that includes the printed circuit board 10 and the solder mask 20. Under certain circumstances, such as during the inspection of the solder mask 20 shortly after its manufacture or during the inspection of an assembly that includes the printed circuit board 10 and the solder mask 20, any damage 23 to the solder mask 20 may be detected.Under other circumstances, such as during the manufacture or use of an electronic device that includes the circuit board 10 and the solder mask 20, damage 23 to the solder mask 20 may remain undetected. In Fig. 3, heat can be applied to the solder mask 20 to repair any damage 23 to the solder mask 20. The heat can be applied in any suitable way. For example, heat can be applied by placing the printed circuit board 10, which carries the solder mask 20, in an oven heated to a suitable temperature. The heat can be applied to selectively repair the damage 23 to the solder mask 20. Alternatively, the heat applied to the solder mask 20 can repair the damage 23 to the solder mask 20 automatically and thus unintentionally. For example, heat can be applied to the solder mask 20 as part of subsequent processing of the printed circuit board 10, which carries the solder mask 20; for example, in a reflow oven when solder electrically connects one or more semiconductor devices (e.g., controllers, memory devices, etc.) to the printed circuit board 10.As another example, heat can be supplied during the operation of an electronic device that includes the circuit board 10 which carries the solder mask 20. The amount of heat applied to the solder mask 20 can be a repair temperature of the curable dielectric material 22 of the solder mask 20. The repair temperature can be approximately 180 °C or less. In some examples, the repair temperature can be in a range of approximately 100 °C to approximately 150 °C or in a range of approximately 100 °C to approximately 130 °C. In some examples, the repair temperature can be an operating temperature of a printed circuit board 10 covered by the solder mask 20, or the temperature of the printed circuit board 10 during the normal operation of an electronic device to which the printed circuit board 10 belongs. When heat is applied to the solder mask 20, bonds in the curable dielectric material 22 of the solder mask 20 can break. These bonds can include hydrogen bonds 26, covalent bonds 27 of a DCP, π-bonds and σ-bonds 28 of a DA adduct, and / or metal-ligand coordination bonds 29 of a metal-ligand coordination polymer. When the bonds break, the curable dielectric material 22 can flow back. The curable dielectric material 22 can flow back into any defects 23 (e.g., scratches, microcracks, cracks, etc.) in the solder mask 20. Once the curable dielectric material 22 flows back into a defect 23, heat can be removed from the solder mask 20 and the curable dielectric material 22, allowing the curable dielectric material 22 to cool. As shown in Fig. 4, as the curable dielectric material 22 cools, the bonds 26, 27, 28, 29 in the curable dielectric material 22 can reform. These bonds can include hydrogen bonds 26, covalent bonds 27 of a DCP, π bonds and σ bonds 28 of a DA adduct, and / or metal-ligand coordination bonds 29 of a metal-ligand coordination polymer. By restoring bonds in the curable dielectric material 22, the complete structural and chemical integrity of the solder mask 20 can be restored, as shown in Fig. 5. The use of a repairable dielectric material 22 to form a solder mask 20 makes it possible to repair damage to the solder mask 20 at any time after its production, including before mounting the printed circuit board 10 on which the solder mask 20 is formed with other devices (e.g., semiconductor devices such as a memory device, a controller, etc.). For example, printed circuit boards 10 that fail testing due to damaged (e.g., scratched, cracked, etc.) solder masks 20 can simply be heated (e.g., placed in an oven, etc.) to repair the damage and then retested. Enabling the reuse of printed circuit boards 10 with damaged solder masks 20 can improve the overall efficiency of the printed circuit board manufacturing process. A solder mask 20 formed from the curable dielectric material 22 can be repaired repeatedly. In some cases, the solder mask 20 formed from the curable dielectric material 22 can be exposed to the repair temperature several times. The use of a curable dielectric material 22 to form a solder mask 20 on a printed circuit board 10 can also maintain the integrity of the solder mask 20 over time, thereby increasing the durability and longevity of the printed circuit board 10 and enhancing the reliability of an electronic device (e.g., an SSD, etc.) into which the printed circuit board 10 has been integrated. Thus, the use of a solder mask 20 formed from the curable dielectric material 22 in an electronic device can reduce the likelihood of needing costly repairs or replacements. Referring to Fig. 6, an example of an electronic device assembly 100 is shown, which includes a printed circuit board (PCB) 110 with conductive traces, which can also be referred to as traces 130, and which consist of a material that can be cured or a curable conductive material 132. Thus, the traces 130 comprise curable conductive traces. The curable conductive material 132 of the traces 130 enables the repair of damage to the traces 130 (e.g., breaks in the conductive traces 130, etc.). The curable conductive material 132 can comprise a high-performance plastic with conductive particles distributed within it. The high-performance polymer of the curable conductive material 132 can be used to define very fine features, such as the traces 130 of a printed circuit board 110, using processes suitable for printed circuit board manufacturing. By incorporating a high-performance polymer into the curable conductive material 132, the traces 130 can be made more flexible than conventional copper traces. This increased flexibility allows the traces 130 to withstand physical stresses better than conventional copper traces and can thus extend the potential lifetime of a printed circuit board 110 that includes traces 130 formed from the curable conductive material 132. Furthermore, the high-performance polymer of the trace 130 can be highly cross-linked, which increases its stability and allows the high-performance polymer to adapt to operating conditions (e.g.,Printed circuit boards (PCBs) are better able to withstand the temperature changes, relatively high operating temperatures, etc., to which they are typically exposed, than conventional copper traces. In one particular example, the high-performance polymer of the curable conductive material 132 can comprise polyimide, which can withstand repeated temperature fluctuations. For example, while conventional PCBs with copper traces can function at operating temperatures up to about 85 °C, a PCB 110 with traces 130 formed from a curable conductive material 132 that includes a polyimide can function at operating temperatures up to about 120 °C; thus, the use of the curable conductive material 132 to define the traces 130 of a PCB 110 can improve the performance of the PCB 110 in demanding environments compared to the performance of a conventional PCB with copper traces in demanding environments.In some examples, the high-performance plastic (e.g., polyimide, etc.) can constitute approximately 79 wt.% to approximately 90 wt.% of the curable conductive material 132. The conductive particles of the curable conductive material 132 can include silver (Ag) and copper (Cu) particles. The particles can be nanoparticles with sizes (e.g., diameter, etc.) ranging from approximately 20 nm to approximately 50 nm. The concentration of conductive particles in the curable conductive material 132 can enable a track 130 formed from the curable conductive material 132 to reliably conduct electrical signals at low voltages, such as the operating voltage (e.g., approximately 3.3 V, approximately 5 V, etc.), of an electronic device assembly 100 that includes the printed circuit board 110. For example, the curable conductive material 132 can have a resistance comparable to that of copper, approximately 1.7 × 10⁻⁸ Ω·m. For example, the curable conductive material 132 can have a specific resistance of about 5.0×10-8Ω m or less.In non-restrictive examples, the conductive particles can constitute approximately 10 wt.% to approximately 15 wt.% of the curable conductive material 132. Optionally, the curable conductive material 132 can include conductive additives that can further improve its electrical properties. Conductive additives can enable the curable conductive material 132 to reliably conduct low-voltage electrical signals. Conductive additives can contribute to the curable conductive material 132's ability to heal and thus to its ability to repair a break in a track 130. Carbon nanotubes and / or graphene can be included in the curable conductive material 132 without restriction. In more specific examples, the curable conductive material 132 can contain both carbon nanotubes and graphene. More precisely, the carbon nanotubes and graphene can each constitute approximately 2 wt% to approximately 3 wt% of the curable conductive material 132. Such a curable conductive material 132 can be used to form traces 130 with widths of about 500 µm to about 1,000 µm and thicknesses of about 20 µm to about 50 µm, compared to the traces of conventional printed circuit boards, which are usually about 1,000 µm wide and about 35 µm thick. In addition to enabling the construction of traces 130 that may be thinner than the copper traces of conventional printed circuit boards (PCBs), the use of a curable conductive material 132 can allow the use of insulating layers that are thinner than those of conventional PCBs. For example, while a conventional PCB with copper traces has insulating layers that are approximately 50 µm thick, a PCB 110 with traces 130 formed from the curable conductive material 132 can be approximately 30 µm thick. Furthermore, tests have shown that traces 130 formed from the curable conductive material 132 fail at a failure rate of only about 1%, in contrast to the 10% failure rate of conventional copper traces, indicating that a PCB 110 with traces 130 formed from the curable conductive material 132 is much more reliable (e.g.,up to about 10 times more reliable) than conventional printed circuit boards with copper traces. Thus, the use of the curable conductive material 132 to form the traces 130 can enable the design and manufacture of printed circuit boards 110 that are considerably thinner and significantly more reliable than conventional printed circuit boards with copper traces. It has been found that such curable conductive material 132 can flow over short distances when exposed to an electric field with voltages exceeding the usual operating voltages of electronic devices. For example, the curable conductive material 132 can flow when exposed to a voltage greater than 5 V. More specifically, the curable conductive material 132 can flow when a voltage greater than 5 V up to about 10 V is applied to it. When the curable conductive material 132 is exposed to such a voltage, it can heat up (e.g., to a temperature of about 120 °C, etc., higher than the normal operating temperature of about 60 °C to about 85 °C), which can cause the curable conductive material 132 to flow. The stress that causes the flow of the curable conductive material 132 can be referred to as the “repair stress”. Applying a repair voltage to a track 130 formed from the curable conductive material 132 can cause the curable conductive material 132 to flow across a fracture 134 (Fig. 7) of up to approximately 10 µm in the track 130. When the curable conductive material 132 flows, it can bridge the fracture 134 and thus restore the functionality of the track 130. Traces 130 formed from the curable conductive material 132 can be repaired repeatedly. In some cases, a trace 130 formed from the curable conductive material 132 can be subjected to the repair voltage several times. With further reference to Fig. 6, the electronic device assembly 100 can additionally include a first semiconductor device 140 and a second semiconductor device 150 on the printed circuit board 110. The traces 130 can establish electrically conductive connections between the first semiconductor device 140 and the second semiconductor device 150, thus enabling communication between the first semiconductor device 140 and the second semiconductor device 150. In examples where the electronic device assembly 100 includes an SSD, the first semiconductor device 140 may include a controller. Such a first semiconductor device 140 may be programmed to control the operation of the electronic device assembly 100 and to enable the electronic device assembly 100 to communicate with other electronic devices. Such a first semiconductor device 140 may also be used to identify any broken or otherwise damaged traces 130 of the printed circuit board 110; for example, the first semiconductor device 140 may include circuits specifically designed and programmed to monitor for problems. Furthermore, such a first semiconductor device 140 may be programmed to apply a repair voltage to one or more broken or otherwise damaged traces 130.While in some examples the first semiconductor device 140 applies a repair voltage to a broken or otherwise damaged track 130 on one side of a break 134 or other damage, the first semiconductor device 140 can also be programmed to cause the second semiconductor device 150 to apply the repair voltage from the other side of the break 134 or other damage to the broken or otherwise damaged track 130. The second semiconductor device 150 of an electronic device assembly 100, which includes an SSD, can be a storage device, for example, a NAND device. In examples where the second semiconductor device 150 can apply a repair voltage to a broken or otherwise damaged track 130, the second semiconductor device 150 can include a multiplier circuit 152. The multiplier circuit can increase or switch the relatively low operating voltage (e.g., about 3.3 V or about 5 V) to a higher repair voltage (e.g., a voltage in the range of above 5 V to about 10 V, etc.). During normal operation, the electronic device assembly 100 (e.g., an SSD, etc.) functions as expected, with electrical signals flowing through the traces 130 of the printed circuit board 110. The first semiconductor device 140 (e.g., a controller, etc.) can monitor the performance of the electronic device assembly 100, including the printed circuit board 110 and its traces 130, ensuring that the electronic device assembly 100 functions optimally (e.g., with optimal read / write speeds and data integrity of the second semiconductor device 150 – a storage device – without interruptions, etc.). While the first semiconductor device 140 continues to monitor the performance of the electronic device assembly 100, it can detect a break 134 or other damage to one or more conductor tracks 130 of the printed circuit board 110, as shown in Fig. 7. By programming the first semiconductor device 140 or dedicated monitoring circuits of the first semiconductor device 140, the first semiconductor device 140 can be enabled to identify a track 130 with a break 134 or other damage. In Fig. 7, two tracks 130, identified in Fig. 7 as track 130a and track 130b, have been broken. As shown in Fig. 8, once a break 134 or other damage to a trace 130a is detected, the first semiconductor device 140 can apply a repair voltage 145 to the trace 130a on one side of the break 134a or other damage. Optionally, the first semiconductor device 140 can cause the second semiconductor device 150, or a multiplier circuit 152 of the second semiconductor device 150, to apply the repair voltage to the trace 130a on the opposite side of the break 134a or other damage. Applying the repair voltage to the trace 130a from opposite sides of the break 134a or other damage ensures that the repairable conductive material 132 flows along the original path of the trace 130a into the break 134a or other damage and not towards other traces 130a or conductive features of the printed circuit board 110.Optionally, the printed circuit board 110 can include an additional insulator next to the sides and / or the underside of each trace 130 to prevent the curable conductive material 132 of the trace 130 from flowing beyond the original path of the trace 130 and potentially causing electrical problems (e.g., short circuits, etc.) between a repaired trace 130 and other electrical features (e.g., other traces 130, etc.) of the printed circuit board 110. The first semiconductor device 140 can monitor the conductivity of track 130a while the break 134a or other damage to track 130a is being repaired. Once track 130a's ability to conduct electrical signals is restored, the first semiconductor device 140 can terminate the repair process. Furthermore, if the repair process continues for a predetermined period without track 130a's ability to conduct electrical signals being restored, the first semiconductor device 140 can terminate the repair process and provide an output indicating that track 130a has been irreparably damaged. Fig. 9 shows the repair of a break 134b in another trace 130b of the printed circuit board 110 in the same manner as described with reference to Fig. 8. The repair of trace 130b can be carried out at least partially simultaneously with the repair of trace 130a or after completion of the repair of trace 130a. The localized electric fields generated by applying the repair voltage to each break can prevent the formation of cross-connections between adjacent breaks 134a and 134b. Fig. 10 shows the electronic device assembly 100 including the repaired traces 130a and 130b. Once a break 134 or other damage to a trace 130 of the printed circuit board 110 has been repaired, normal operation of the electronic device assembly 100 can be resumed. Some examples of a printed circuit board may include at least one solder mask 20 formed from a curable dielectric material 22 as described with reference to Fig. 1, and traces 130 formed from a curable conductive material 132 of the type described with reference to Fig. 6. Similarly, some examples of electronic device assemblies, such as the electronic device assembly 100 described with reference to Fig. 6, may include a printed circuit board 10, 110 with at least one solder mask 20 formed from a curable dielectric material 22 as described with reference to Fig. 1, and traces 130 formed from a curable conductive material 132 as described with reference to Fig. 6. Based on the foregoing, examples in this disclosure describe a printed circuit board (PCB) comprising at least one of the following elements: a solder mask comprising a curable dielectric material that flows at a repair temperature at or above the operating temperature of an electronic device into which the PCB is to be installed; and traces defined by a curable conductive material that flows when a repair voltage is applied to a trace of the traces, the repair voltage exceeding an operating voltage of the electronic device into which the PCB is to be installed. In one example, the solder mask includes a base resin, at least one thermoplastic resin, and at least one heat-activated reversible polymer (HARP).In one example, the at least one HARP includes a dynamic covalent polymer (DCP), a Diels-Alder adduct (DA adduct), and / or a metal-ligand coordination polymer. In another example, the repair temperature is in the range of 100 °C to 130 °C. In yet another example, the curable conductive material comprises a polyimide with silver and copper nanoparticles distributed throughout the polyimide. In yet another example, at least one of the silver nanoparticles and one of the copper nanoparticles have sizes in the range of 20 nm to 50 nm. In yet another example, the polyimide further comprises at least one carbon nanotube and one graphene nanotube. In yet another example, the repair voltage is in the range of 5 volts (V) to 10 V.In one example, the printed circuit board (PCB) carries a controller and a memory device. The controller is programmed to monitor the PCB's performance, detect a break in the trace, and apply the repair voltage to the trace from a first side of the break. In another example, the memory device includes a multiplier circuit; and the controller is further programmed to cause the memory device's multiplier circuit to apply the repair voltage to the trace on a second side of the break, opposite the first side of the break. Examples also describe a method for repairing a break in a trace of a printed circuit board (PCB), comprising: identifying the trace with the break and applying a repair voltage to the trace to repair the break, wherein the repair voltage exceeds an operating voltage of an electronic device in which the PCB is provided. In one example, applying the repair voltage includes applying a voltage in the range of 5 V to 10 V to the break. In another example, applying the repair voltage includes applying the repair voltage to the trace from opposite sides of the break. In yet another example, applying the repair voltage from opposite sides of the break includes: applying the repair voltage from a first side of the break with a processor communicating with the trace; and applying the repair voltage from a second side of the break.In one example, applying the repair voltage from the second side of the fracture involves applying the repair voltage from a multiplier circuit connected to the electronic device. Examples also describe a method for repairing damage to a solder mask on a printed circuit board (PCB), comprising: detecting damage to the solder mask; applying heat to the damage, including: breaking Diels-Alder bonds in the solder mask material; breaking hydrogen bonds in the solder mask material and dissolving metal-ligand bonds in the solder mask material; and cooling the solder mask material, including: restoring Diels-Alder bonds in the solder mask material; restoring hydrogen bonds in the solder mask material and reforming metal-ligand bonds in the solder mask material. In one example, applying heat to the damage includes applying heat to the entirety of the solder mask. In another example, applying heat includes exposing the solder mask to a temperature in the range of 100 °C to 130 °C.In one example, the circuit board is enclosed in a data storage device. In another example, heat is applied during the operation of the data storage device. The description and illustration of one or more aspects of the present disclosure are not intended to restrict or limit the scope of the disclosure in any way. The aspects, examples, and details provided in this disclosure are considered sufficient to convey knowledge and enable others to make and use the claimed disclosure in the best possible way. The claimed disclosure should not be interpreted as being limited to one aspect, example, or detail provided herein. Regardless of whether they are shown and described in combination or separately, the intention is that the various features (both structural and methodological) may be selectively rearranged, included, or omitted to create an example with a particular set of features. After receiving the description and illustration of the present disclosure, the person skilled in the art may conceive of variations, modifications, and alternative aspects that are consistent with the spirit of the broader aspects of the general concept of the invention embodied in this disclosure and that do not deviate from the wider scope of the claimed disclosure. References to an element herein using a label such as "first," "second," etc., do not generally restrict the set or order of those elements. Rather, these labels can be used as a method of distinguishing between two or more elements or instances of an element. Thus, a reference to a first and second element does not imply that only two elements may be used or that the first element precedes the second. Furthermore, unless otherwise specified, a set of elements may include one or more elements. The terminology used in the description or claims in the form of "at least one of A, B, or C" or "A, B, C, or any combination thereof" means "A, B, or C, or any combination of these elements." This terminology may include, for example, A, B, C, A and B, A and C, A and B and C, 2A, 2B, 2C, 2A, and B, etc. As a further example, "at least one of: A, B, or C" is intended to cover A, B, C, AB, AC, BC, and ABC, as well as multiples of the same elements. Similarly, "at least one of: A, B, and C" is intended to cover A, B, C, AB, AC, BC, and ABC, as well as multiples of the same elements. Similarly, a phrase referring to a list of elements linked by "and / or," as used here, refers to any combination of the elements. For example, "A and / or B" is meant to cover A alone, B alone, or A and B together. As another example, "A, B and / or C" is meant to cover A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B, and C together.

Claims

Printed circuit board (PCB), comprising at least one of: a solder mask comprising a curable dielectric material that flows at a repair temperature equal to or above an operating temperature of an electronic device into which the PCB is to be installed; and traces defined from a curable conductive material that flows when a repair voltage is applied to a trace of the traces, the repair voltage exceeding an operating voltage of the electronic device into which the PCB is to be installed. Printed circuit board according to claim 1, wherein the solder mask includes a base resin, at least one thermoplastic resin and at least one heat-activated reversible polymer (HARP). Printed circuit board according to claim 2, wherein the at least one HARP includes a dynamic covalent polymer (DCP), a Diels-Alder adduct (DA adduct) and / or a metal-ligand coordination polymer. Printed circuit board according to claim 1, wherein the repair temperature is in a range of 100 °C to 130 °C. Printed circuit board according to claim 1, wherein the curable conductive material comprises a polyimide with silver nanoparticles and copper nanoparticles distributed throughout the polyimide. Printed circuit board according to claim 5, wherein at least one of the silver nanoparticles and the copper nanoparticles have sizes in a range between 20 nm and 50 nm. Printed circuit board according to claim 5, wherein the polyimide further comprises at least one of carbon nanotubes and graphene. Printed circuit board according to claim 5, wherein the repair voltage is in a range between 5 volts (V) and 10 V. Printed circuit board according to claim 1, which carries a controller and a storage device, wherein the controller is programmed to monitor the performance of the printed circuit board, detect a break in the trace and apply the repair voltage from a first side of the break to the trace. Printed circuit board according to claim 9, wherein: the storage device includes a multiplier circuit and the controller is further programmed to cause the multiplier circuit of the storage device to apply the repair voltage to the track on a second side of the fracture opposite the first side of the fracture. Method for repairing a break in a trace of a printed circuit board (PCB), comprising: identifying the trace with the break and applying a repair voltage to the trace to repair the break, wherein the repair voltage exceeds an operating voltage of an electronic device in which the printed circuit board is provided. Method according to claim 11, wherein the application of the repair voltage comprises applying a voltage in a range between 5 V and 10 V to the fracture. Method according to claim 11, wherein the application of the repair voltage comprises the application of the repair voltage to the track from opposite sides of the fracture. The method of claim 13, wherein the application of the repair voltage from opposite sides of the fracture comprises: applying the repair voltage from a first side of the fracture with a processor communicating with the track; and applying the repair voltage from a second side of the fracture. Method according to claim 14, wherein applying the repair voltage from the second side of the fracture comprises applying the repair voltage from a multiplier circuit connected to the electronic device. Method for repairing damage to a solder mask on a printed circuit board (PCB), comprising: detecting damage to the solder mask; applying heat to the damage, including: breaking Diels-Alder bonds in the solder mask material; breaking hydrogen bonds in the solder mask material and dissolving metal-ligand bonds in the solder mask material; and allowing the solder mask material to cool, including: restoring Diels-Alder bonds in the solder mask material; restoring hydrogen bonds in the solder mask material and reforming metal-ligand bonds in the solder mask material. Method according to claim 16, wherein the application of heat to the damage comprises the application of heat to the entirety of the solder mask. The method of claim 16, wherein the application of heat comprises exposing the solder mask to a temperature in the range between 100 °C and 130 °C. Method according to claim 16, wherein the printed circuit board is enclosed in a data storage device. Method according to claim 19, wherein the application of heat takes place during the operation of the data storage device.

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