Patent Description:
This disclosure relates generally to the use of different types of moisture-resistant materials in combination. More specifically, this disclosure relates to protective coatings that include two or more types of moisture-resistant materials, and to moisture-sensitive substrates that include such protective coatings. This disclosure also relates to moisture-sensitive substrates with different types of moisture-resistant materials on different elements.

<CIT> describes an electrical or electro-optical assembly comprising a substrate comprising an insulating material, at least one conductive track present on at least one surface of the substrate, at least one electrical or electro-optical component connected to at least one of the at least one conductive track, and a continuous coating comprising one or more plasma-polymerized polymers completely covering the at least one surface of the substrate, the at least one conductive track and the at least one electrical or electro-optical component.

<CIT> describes intermetal dielectric and interlevel dielectric that have dielectric constants ranging from <NUM> to <NUM> and are prepared from plasma or photon assisted CVD (PACVD) or transport polymerization (TP). The materials are prepared from PACVD or TP of some selected siloxanes and F-containing aromatic compounds.

<CIT> describes a method for depositing a parylene polymer barrier coating on a polymeric substrate. The method comprises the steps of thoroughly treating a surface portion of the substrate to remove any contaminants, depositing at least one layer of parylene polymer on the contaminant-free surface portion via chemical vapor deposition, and then annealing each of the at least one layer of parylene polymer for a sufficient time.

The present invention is featured in the appended claims.

As used herein, the terms "moisture-resistant" and "moisture-resistance" refer to the ability of a coating to prevent exposure of a coated element or feature to moisture. As an example, a moisture-resistant coating may resist wetting or penetration by one or more types of moisture, or it may be impermeable to one or more types of moisture or substantially impermeable to one or more types of moisture-the term "substantially" indicating that over long durations of time, some moisture may migrate through the coating. Both moisture impermeable and substantially moisture impermeable barriers are, for the sake of simplicity, referred to herein as "moisture impermeable" barriers. As another example, a moisture-resistant coating may repel one or more types of moisture; for example, it may the moisture-resistant coating may have an outer surface that is configured (e.g., structurally (e.g., lotus leaf-type structures, etc.), chemically (e.g., hydrophobic materials, etc.), etc.) to repel moisture.

In some embodiments, a moisture-resistant coating may be impermeable to, substantially impermeable to and/or repel water, an aqueous solution (e.g., salt solutions, acidic solutions, basic solutions, drinks, etc.) or vapors of water or other aqueous materials (e.g., humidity, fogs, mists, etc.), wetness, etc.). Use of the term "moisture-resistant" to modify the term "coating" should not be considered to limit the scope of materials from which the coating protects one or more components of an electronic device. The terms "moisture-resistant" and "moisture-resistance" may also refer to the ability of a coating to restrict permeation of or repel organic liquids or vapors (e.g., organic solvents, other organic materials in liquid or vapor form, etc.), as well as a variety of other substances or conditions that might pose a threat to a substrate (e.g., a moisture-sensitive substrate, etc.), such as an electronic device or its components.

In general, this disclosure relates to protective coatings. A protective coating according to this disclosure may include two or more different types of moisture-resistant materials. In some embodiments, the two or more different types of moisture-resistant materials may comprise discernibly discrete portions (e.g., sub-layers, etc.) of the protective coating. In other embodiments, the protective coating may include a gradient, or gradual transition, between two or more different types of moisture-resistant materials.

Methods for forming such a protective coating are also disclosed. Such a method may include separately defining (e.g., depositing, etc.) portions of a protective coating. Alternatively, two or more types of moisture-resistant materials may be co-deposited. As another option, different types of moisture-resistant materials may be deposited in a sequential, overlapping manner, which may result in coatings that include material gradients, or are graded.

According to this disclosure, a substrate may include at least one protective coating that includes two or more different moisture-resistant materials. In embodiments where the first type of moisture-resistance includes impermeability to moisture and the second type of moisture-resistance includes moisture-repellence, the second type of moisture-resistance may be disposed atop the first type of moisture-resistance. Alternatively, the second type of moisture-resistance may be located closer than the first type of moisture-resistance to a substrate, such as a component or other feature of an electronic device.

In addition, or as an alternative, a substrate may include different elements that are protected by protective coatings formed from different types of moisture-resistant materials. In a specific embodiment, a moisture-repellant material may be applied to some elements, while a moisture barrier may be applied to other elements.

Such an embodiment of moisture-resistant protection may be particularly useful for protecting state of the art mobile electronic devices from accidental or incidental exposure to moisture. One material may provide the primary type of moisture-resistance-a moisture-impermeable coating or barrier that covers and seals or substantially seals at least some moisture-sensitive components or other features within the interior of an electronic device in a manner (e.g., confluently, etc.) that will prevent moisture from contacting those components or other features, should moisture enter into the interior of the electronic device. However, confluent coatings may have a detrimental effect on the performance or even the operation of some components of an electronic device (e.g., microphones, speakers, optical elements, etc.). Nonetheless, those components and/or the electronic device(s) of which they are a part may benefit from moisture resistance (e.g., by preventing moisture from entering into the interior of such a component, into the interior of the electronic device of which the component is a part, etc.).

The secondary type of moisture resistance provided by another material may not provide the same degree of resistance to moisture as the primary type of moisture resistance. In any event, the material providing the secondary type of moisture resistance may be used to coat components or other features that are not compatible with the primary type of moisture resistance, but are compatible with a less protective type of moisture resistance. Providing components or other features with the secondary type of moisture resistance will impart those components or features with at least some ability to withstand exposure to moisture, which is better protection than those components or features would receive if they were to lack protection against moisture. Some embodiments of the secondary layer may be configured to enable electrical communication therethrough; for example, a secondary layer may be electrically conductive or it may be too thin to prevent electricity from passing therethrough. In other embodiments, the thickness (or thinness) of the secondary layer may enable its ready removal from electrically conductive features (e.g., communication ports, contacts, etc.) to expose the same and, thus, to facilitate electrical connections to the exposed electrically conductive features.

In other various embodiments, the substrate may comprise an industrial device, a vehicular device, a precision mechanical device, a medical device, a scientific instrument, an article of clothing or the like.

Generally, some components or features of a moisture-sensitive substrate, such as an electronic device, may lack a moisture-resistant coating or barrier. These components or feature may include, but are not limited to, surfaces of components and/or features exposed to an exterior of the moisture-sensitive substrate, as well as components and/or features located within an interior of the moisture-sensitive substrate.

Other aspects, as well as features and advantages of the disclosed subject matter will be apparent to those of ordinary skill in the art through consideration of this disclosure and the appended claims.

With reference to <FIG>, an embodiment not according to the invention of a protective coating <NUM> is illustrated. The protective coating <NUM> may, as illustrated, comprise a film, although other configurations of protective structures are also within the scope of this disclosure. The protective coating <NUM> includes at least two different materials <NUM>, <NUM>, etc., and is configured to provide moisture-resistance. In protective coating <NUM>, the materials <NUM>, <NUM> define different portions of the protective coating <NUM>, such as the sub-layers or sub-coatings illustrated by <FIG>. In such an embodiment, a visibly discernible boundary <NUM> may exist between the discrete portions that are defined by two different materials <NUM> and <NUM>.

<FIG> illustrates an embodiment of protective coating <NUM>' used in the invention. Instead of a discernible boundary <NUM> (<FIG>), protective coating <NUM>' includes a transition <NUM>', or gradient, between two or more materials <NUM> and <NUM>. Thus, a base <NUM>' of the protective coating <NUM>' may consist of or consist essentially of a first material <NUM>, and an outer surface <NUM>' of the protective coating <NUM>' may consist of or consist essentially of a second material <NUM>, but at least some regions therebetween, such as the transition <NUM>, include two or more materials, such as material <NUM> and material <NUM>.

As illustrated by <FIG>, protective coatings <NUM>" that include one or more materials <NUM> that define a corresponding number of discrete portions, as well as two or more materials <NUM> and <NUM> that define a portion with a transition <NUM>', are also within the scope of this invention.

The two or more portions of a protective coating <NUM>, <NUM>', <NUM>" may be superimposed across an entire extent of the protective coating <NUM>, <NUM>', <NUM>" or across substantially all of the protective coating <NUM>, <NUM>', <NUM>".

In some embodiments, each material <NUM>, <NUM>, <NUM> of a protective coating <NUM>, <NUM>', <NUM>" may comprise a moisture-resistant material. Alternatively, an outermost material <NUM>, <NUM> may comprising a capping material that may protect and/or enhance a moisture-resistant property of an underlying moisture-resistant material <NUM>, <NUM>. As another alternative, a material <NUM> at a base of the protective coating <NUM>, <NUM>', <NUM>" may promote adhesion between a moisture-resistant material <NUM> and a substrate <NUM>, <NUM>' (<FIG>, respectively). Optionally, a portion of a protective coating <NUM>, <NUM>', <NUM>" (e.g., material <NUM>, material <NUM>, material <NUM>, etc.) may impart the protective coating <NUM>, <NUM>', <NUM>" with at least one desired characteristic (e.g., thermal conductivity, electrical insulation, a desired texture, a desired surface finish, etc.).

In some embodiments where at least two materials <NUM>, <NUM>-and the corresponding portions-of a protective coating <NUM>, <NUM>', <NUM>" comprise moisture-resistant materials, both materials <NUM>, <NUM> may provide the same type or similar types of moisture resistance. As an example, materials <NUM> and <NUM> may both be substantially impermeable to water or impermeable to water, although material <NUM> may have a different impermeability to water than material <NUM>. In addition to providing the same type or substantially the same type of moisture-resistance, one of the materials <NUM>, <NUM> may provide an additional type of moisture resistance from the other of the materials <NUM>, <NUM>. As an example, material <NUM> may be moisture-impermeable, while material <NUM> may be impermeable to moisture and repel moisture. According to the invention, a material <NUM> at the base of a protective coating <NUM>, <NUM>', <NUM>" is formed from parylene C, which is a poly(p-xylylene) in which some hydrogens have been replaced with chlorine, while a material <NUM> at an outer portion of the protective coating <NUM>, <NUM>', <NUM>" includes a parylene with some fluorine substitutions. The fluorine substitutions may impart the outer portion of the protective coating <NUM>, <NUM>', <NUM>" with added moisture repellence.

In other embodiments where at least two materials <NUM>, <NUM>-and the corresponding portions-of a protective coating <NUM>, <NUM>', <NUM>" comprise moisture-resistant materials, the materials <NUM>, <NUM> of the protective coating <NUM>, <NUM>', <NUM>" may provide different types of moisture-resistance from one another. Such a protective coating <NUM>, <NUM>', <NUM>" may provide a primary type of protection for a majority of the moisture sensitive elements, or components, of a substrate and a secondary type of protection for elements, or components, of the substrate that do not perform as desired or that are otherwise incompatible with the primary type of protection.

In a specific embodiment, the primary type of protection may comprise a coating or other barrier material that is moisture-impermeable. Such a coating may have a thickness that imparts it with a desired amount of impermeability to moisture. A coating formed from such a moisture-impermeable material may have a thickness of about <NUM> (micrometer, or micron) to about <NUM>.

The secondary type of protection of such an embodiment may comprise a material that repels moisture. By way of example, and not by way of limitation, the secondary coating may comprise an ultrathin (with a layer thickness of about <NUM>Ǻ or less) moisture-repellent material. Optionally, moisture repellence may be achieved with films or other structures that include moisture-repellent surface features (e.g., so-called "lotus leaf" structures, other structures that impart a surface with moisture repellence, etc.).

According to the invention, with reference to <FIG>, , material <NUM> comprises parylene C, while material <NUM> comprises a fluorinated parylene, which is a fluorinated polymer, or "fluoropolymer".

Generally, a variety of embodiments of moisture-impermeable materials may be used in a protective coating <NUM>, <NUM>', <NUM>" according to this disclosure. According to the invention, the polymer of a moisture impermeable barrier comprises a substituted poly (p-xylylene), which is more commonly referred to as "parylene. " Material that may form a moisture impermeable (e.g., watertight, etc.) film or structure that will adhere to its intended substrate (e.g., a component configured to be within an interior of an electronic device, etc.) over time, during prolonged and/or repeated use of the substrate, while not having a detrimental effect on the substrate and without interfering with the function of the substrate may be used to form a moisture impermeable barrier.

Various types of moisture-repellent materials that may be used in a protective coating <NUM>, <NUM>', <NUM>" according to this disclosure include materials that are compatible with, and that will adhere and remain adhered to other portions of a coating (e.g., adhesion promoters, moisture-impermeable materials, protective materials, etc.). The moisture-repellent characteristics of that material of the protective coating <NUM>, <NUM>', <NUM>" may be attributable to one or more factors, including, but not limited to, the chemical properties of a material from which the moisture-repellent portion of the coating is formed, surface features of a moisture-repellant film or other moisture-repellant structure formed by the material (e.g., so-called "lotus leaf" structures, other structures that impart a surface with hydrophobicity and/or moisture-repellence, etc.), an electronegativity of the material and/or surface of the moisture-repellent portion, or any other property that contributes to moisture-repellency.

According to the invention, the outer portion of the coating comprises fluorinated parylenes (e.g., parylene AF-<NUM>, etc.). Some embodiments of the hydrophobic or moisture repellent portion of a coating may comprise a hydrophobic or superhydrophobic material with a rough (e.g., microstructured, nanostructured, etc.) surface. Moisture-repellant nanoparticles may also be used as a material <NUM>, <NUM> of a protective coating <NUM>, <NUM>', <NUM>".

As indicated previously herein, a protective coating <NUM>, <NUM>', <NUM>" may include a material <NUM> that promotes adhesion of the protective coating <NUM>, <NUM>', <NUM>" or a portion thereof to a substrate or to another portion of the protective coating <NUM>, <NUM>', <NUM>". Such an adhesion-promoting material may be selected on the basis of its ability to adhere to the structures between which the adhesion promote resides (i.e., the substrate and a base portion of the protective coating <NUM>, <NUM>', <NUM>", two portions of the protective coating <NUM>, <NUM>', <NUM>", another coating on an outer surface of the protective coating <NUM>, <NUM>', <NUM>", etc.). A variety of materials may be used to enhance adhesion and/or for any of a variety of other purposes, including, without limitation, ceramic materials, such as aluminum oxide (Al<NUM>O<NUM>), which is also commonly referred to as "alumina," boron nitride, or any of a variety of other materials.

Some non-limiting examples of capping materials that may be used as the outermost material <NUM>, <NUM> of a protective coating <NUM>, <NUM>', <NUM>" include aluminum oxide, diamond-like carbon (e.g., pure carbon, hydrogenated carbon, fluorinated carbon, nitrogenized carbon, phosphorylated carbon, etc., or combinations of any of the foregoing), silicon nitride, a metal oxide such as hafnium (IV) oxide (HfO<NUM>), yttrium oxide (Y<NUM>O<NUM>) or zirconium dioxide (ZrO<NUM>) or the like. As indicated previously herein, such a material may harden or toughen the surface of a protective coating <NUM>, <NUM>', <NUM>", cover passageways through another material <NUM>, <NUM> (e.g., a parylene, another moisture-impermeable material, etc.) of the protective coating <NUM>, <NUM>', <NUM>", or otherwise enhance the functionality, durability (e.g., hardness, impact resistance, scratch resistance, abrasion resistance, wear resistance, etc.), etc., of the protective coating <NUM>, <NUM>', <NUM>".

Turning now to <FIG>, embodiments substrates <NUM>, <NUM>', respectively, that include one or more protective coatings <NUM>, <NUM>', <NUM>" are illustrated and described.

<FIG> shows an embodiment of a substrate <NUM>; for example, a printed circuit board <NUM> carrying electronic components <NUM>, <NUM>, <NUM>. One or more protective coatings <NUM>, <NUM>', <NUM>" cover selected areas of the substrate <NUM>. In the depicted embodiment, a protective coating <NUM>, <NUM>', <NUM>" covers components <NUM> and <NUM>, as well as a portion of the top side <NUM> of the printed circuit board <NUM> exposed between the components <NUM> and <NUM>. In some embodiments, other areas of the substrate <NUM>, such as the portion of the top side <NUM> of the printed circuit board <NUM> located between component <NUM> and component <NUM>, and the component <NUM>, may remain uncoated (i.e., no protective coating <NUM>, <NUM>', <NUM>") is located over these areas of the substrate <NUM>). In addition, peripheral edges <NUM> of the printed circuit board <NUM> and a back side <NUM> of the printed circuit board <NUM> may be exposed.

In some embodiments, a plurality of different types of protective coatings may cover different areas of a substrate. <FIG> is a representation of a substrate <NUM>', such as an assembly or subassembly of an electronic device (e.g., a mobile electronic device, such as a smart phone, a tablet computing device, a digital media player, etc.). The substrate <NUM>' of <FIG> includes a printed circuit board <NUM> that carries various components <NUM>, <NUM>, <NUM>, <NUM>. In the depicted embodiment, a protective coating <NUM>, <NUM>', <NUM>" that includes two or more materials <NUM>, <NUM> (<FIG>) may cover some areas of the substrate <NUM>', such as components <NUM> and <NUM>, as well as a portion of the printed circuit board <NUM> located therebetween. A protective coating that consists of or that consists essentially of a single material <NUM> may coat another of the components <NUM> of the substrate <NUM>', while another protective coating that consists of or that consists essentially of another single material <NUM> may coat yet another component <NUM>.

In a more specific embodiment, material <NUM> may comprise a moisture-impermeable material and may be used to protect moisture-sensitive components <NUM>, <NUM>, <NUM> whose operation may remain substantially unimpeded by a coating of such a material <NUM>. Material <NUM> may comprise a moisture-repellant material, which may be applied over areas of material <NUM> that overlie particularly moisture-sensitive components <NUM>, <NUM>. In addition, such a material <NUM> may be applied directly to components <NUM> that will benefit from moisture resistance, but whose operation would be impeded by a coating of a moisture-impermeable material <NUM>. Examples of such components include, but are certainly not limited to, microphones, speakers, optical elements, and the like. Of course, a substrate <NUM>' may include any combination of protective coatings; the immediately preceding disclosure should not be considered to limit the manner in which protective coatings may be combined.

As illustrated by <FIG>, the protective coating(s) <NUM>, <NUM>', <NUM>" and/or material(s) <NUM>, <NUM> may be confined or substantially confined to components within the interior <NUM>, <NUM>' of an electronic device <NUM>, <NUM>', such as within the interior of the housing or other external components of an electronic device. In other embodiments, a protective coating <NUM>, <NUM>', <NUM>" and/or material <NUM>, <NUM> may cover at least some components that are exposed to the outside of the electronic device <NUM>, <NUM>'.

Methods for applying one or more materials <NUM>, <NUM>, <NUM> and/or protective coatings <NUM>, <NUM>', <NUM>" to a substrate <NUM>, <NUM>' are also disclosed. Two or more materials <NUM>, <NUM> may be applied in a single process. When a single process is used to apply different materials <NUM>, <NUM> the materials <NUM>, <NUM> may be chemically similar to one another. With returned reference to <FIG>, for the protective coating <NUM>' in which the material <NUM> of a base portion comprises parylene C and the material <NUM> of an outer portion comprises a fluorinated parylene, the deposition process may start with precursors to the parylene C and transition to precursors for the fluorinated parylene. As the deposition process is initiated, all the precursors comprise precursors to the parylene C. If the transition between precursors to parylene C and fluorinated parylene is abrupt, the resulting protective coating <NUM> may resemble that illustrated by <FIG>. If the transition is gradual, the resulting protective coating <NUM>' may resemble that depicted by <FIG>. At the conclusion of the deposition process, all of the precursors comprise precursors to the fluorinated parylene.

Alternatively, such a method may include two or more discrete processes in which different materials <NUM>, <NUM>, <NUM> (<FIG>) are applied to a substrate <NUM>, <NUM>' (<FIG>). The discrete processes may be carried out by the same equipment, even in the same application zone (e.g., deposition chamber, etc.), or by separate apparatuses (e.g., a chemical vapor deposition (CVD) chamber for parylene, including fluorinated parylenes; a plasma-enhanced CVD (PECVD) chamber for some fluoropolymers, for a diamond-like coating or for aluminum oxide; an atomic layer deposition (ALD) chamber for some fluoropolymers, for a diamond-like coating or for aluminum oxide; etc.) may be used to effect the discrete processes.

In some embodiments, a coating method may also include the application of a mask to selected regions of the substrate to prevent at least one portion of the coating from being applied to those portions. In embodiments where discrete processes are used to form different portions of a coating, the mask may be present while at least one material <NUM>, <NUM>, <NUM> (<FIG>) is applied to the substrate <NUM>, <NUM>' (<FIG>), but absent while at least one other material <NUM>, <NUM>, <NUM> is applied to the substrate; thus, some (masked) portions of the substrate <NUM>, <NUM>' will be covered by fewer portions of a coating than other (unmasked) portions of the substrate. In other embodiments, a mask may remain in place as all materials <NUM>, <NUM>, <NUM> are applied to the substrate <NUM>, <NUM>'. As a result, none of the materials <NUM>, <NUM>, <NUM> will cover those areas of the substrate <NUM>, <NUM>'.

Claim 1:
An electronic device, comprising:
a housing defining an interior and an exterior of the electronic device;
a plurality of electronic components exposed to the interior of the electronic device;
and
a coating for imparting electronic components with moisture resistance covering at least portions of at least some electronic components of the plurality of electronic components, said coating comprising:
a base portion comprising a moisture-impermeable barrier providing a first type of moisture resistance, the base portion comprising parylene C, all the precursors for the base portion comprising precursors to parylene C; and
an outer portion providing another type of protection, the outer portion comprising a fluorinated parylene, all the precursors for the outer portion comprising precursors to the fluorinated parylene; and
a transition between the base portion and the outer portion, the transition comprising parylene C and the fluorinated parylene, the transition being a gradient between parylene C and the fluorinated parylene.