Structures and methods related to detection, sensing, and/or mitigating undesirable structures or intrusion events on structures

A method and an apparatus for mitigating electrical failures caused by intrusive structures. Such structures can be tin whiskers forming on electrical circuits. In an illustrative embodiment, nano-capsules are filled with some type of insulative and adhesive fluid that is adapted to bind to and coat an intrusive structure, e.g., a whisker, making the whisker electrically inactive and thereby reducing the electrical faults that can be caused by the whisker. In another illustrative embodiment, randomly oriented nano-fibers having an elastic modulus higher than tin or any other whisker material is used to arrest a growth or movement of a whisker and further reduce a likelihood that a whisker can cause an electrical fault.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to the sensing or detection of undesirable structures or intrusion events, such as tin whiskers, a tampering event, or an attempt to create a counterfeit device through alteration or unauthorized use of an electronic device, using a variety of structures and processing techniques. Current types of conformal coatings as applied on circuit boards are not able to prevent undesirable structure growth, such as tin or other whisker growth, through them. Furthermore, the undesirable structures that grow from current conformal coatings are problematic since they can create many short circuits and failures by conducting undesired current through them. One aspect or embodiment of the invention addresses this issue by providing a nano-fiber textile matrix above the conformal coated circuit board or by providing a conformal coat possessing a material such as a nano-fiber textile. Another embodiment of this invention utilizes encapsulating structures such as micro- or nano-tubes or micro- or nano-capsules containing a chemical fluid, such that when the undesirable structure ruptures the encapsulating structures, the fluid coats the undesirable structure with an electrically insulative layer. Thus, if the whisker emerges from the coating surface, it will have an electrically insulating coating material on its surface, rendering it electrically inactive and preventing electrical conduction.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring initially toFIG. 1, a simplified structure in accordance with one aspect or embodiment of the invention is shown. A printed circuit board (PCB)5is provided with a conformal coating3as a first layer and a randomly oriented nano-fiber composite textile layer with elastic modulus higher than tin or any other whisker material1formed on top of the conventional conformal coating3as a second layer. Alternatively, the PCB5is provided with the conformal coating3as a first layer and a second layer7formed on it comprising a randomly or non-randomly oriented nano-fiber composite textile with elastic modulus higher than tin or any other whisker material, where the elastic modulus is a measure of stiffness of an elastic material, and containing nano-capsules or nano-tubes containing electrically insulative liquid. An alternative embodiment for conformal coating3is that of a tin finish or a solder coating.

Referring toFIG. 2, a simplified structure in accordance with one aspect or embodiment of the invention is shown. A PCB15is provided with a conformal coating as a first layer12and with a second layer13formed on it comprising a randomly or non-randomly oriented nano-fiber composite textile with elastic modulus higher than tin or any other whisker material. Since the second layer13is composed of a material having an elastic modulus higher than tin or any other whisker material, as a whisker19grows or moves, the second layer13is likely to cause the whisker19to be deformed, bent, redirected, or to cause the movement of the whisker19to be slowed or stopped. The second layer13can act as a physical impediment to the whisker19and is a form of mechanical mitigation preventing the whisker19from creating electrical faults.

Referring toFIG. 3, a simplified structure in accordance with one aspect or embodiment of the invention is shown. A PCB31is provided with a conformal coating as a first layer32and a second layer33formed on the first layer32comprising a randomly or non-randomly oriented nano-fiber composite textile layer35with elastic modulus higher than tin or any other whisker material and nano-capsules39containing an electrically insulative liquid. The electrically insulative liquid is transferred from the nano-capsules39to the surface of a whisker41so that the whisker41is coated by an electrically insulative layer. The whisker41, or other undesirable or intrusive structure, is rendered electrically inactive by the electrically insulative layer such that the whisker41, or other undesirable or intrusive structure, will not cause electrical faults or short-circuits.

Referring toFIG. 4, a simplified structure in accordance with one aspect or embodiment of the invention is shown. A PCB45is provided with a conformal coating as a first layer43and a second layer46comprising a randomly or non-randomly oriented nano-fiber composite textile47with elastic modulus higher than tin or any other whisker material and nano-tubes48containing an electrically insulative liquid. When a whisker49, or other undesirable structure or material, cracks or punctures the nano-tubes48, the electrically insulative liquid leaks out and is transferred from the nano-tubes48to the surface of the whisker49so that the whisker49is coated with an insulative coating layer50of the electrically insulative liquid. The whisker49, or other undesirable structure or material, is rendered electrically inactive by the insulative coating layer50such that the whisker49, or other undesirable structure or material, will not cause electrical faults or short-circuits.

Referring toFIG. 5, a simplified structure in accordance with one aspect or embodiment of the invention is shown. A PCB55is provided with a conformal coating as a first layer52, a second layer53comprising nano-tubes or nano-capsules containing an electrically insulative liquid and a third layer51comprising a randomly or non-randomly oriented nano-fiber composite textile with elastic modulus higher than tin or any other whisker material. When a whisker57, or other undesirable structure or material, cracks or punctures the nano-tubes or nano-capsules in the second layer53, the electrically insulative liquid leaks out and is transferred from the nano-tubes or nano-capsules to the surface of the whisker57, so that the whisker57is coated with an insulative coating layer59of the electrically insulative liquid. The whisker57, or other undesirable structure or material, is rendered electrically inactive by the insulative coating layer59such that the whisker57, or other undesirable structure or material, will not cause electrical faults or short-circuits. In one embodiment, the insulative chemical or liquid in the tubes can be injected into the tubes or containment structure under pressure to facilitate coating action of the chemical on the intrusive or undesirable structure. Additionally, alternative embodiments provide the insulative chemical or liquid inside a structure other than a tube but that performs the same or similar functions and provides similar multiple effects as the tube described herein (e.g., multi-intrusion vector diversion, selective action, insulator coating, capture effect, accelerant effect, etc.). For example, an exemplary liquid or chemical in accordance with one embodiment of the invention can also be formed within laminated or multi-walled containment structures, e.g., tubes, which have additional chemical or liquids which facilitate coating of the intrusive structures such as a material which accelerates drying or persistent coating of such intrusive structures e.g., tin whiskers.

The third layer51comprising a randomly or non-randomly oriented nano-fiber composite textile with elastic modulus higher than tin or any other whisker material can also act as a kind of barrier to the whisker57. The third layer51can cause the whisker57to be deformed, bent, redirected, or to cause the movement of the whisker57to be slowed or stopped. Thus, the third layer51can act as a physical impediment to the whisker57and is a form of mechanical mitigation preventing the whisker57from creating electrical faults. The second layer53and third layer51can work together to ensure the whisker57does not create electrical faults by both physically preventing the whisker57from being able to contact other conducting materials and by coating the whisker57with an insulating material that causes the whisker57to be electrically inactive. In another embodiment of the invention, the third layer51can be between the first layer52and the second layer53.

Referring toFIG. 6, a simplified structure in accordance with one aspect or embodiment of the invention is shown. A PCB65is provided with a conformal coating as a first layer67, a second layer69comprising nano-tubes or nano-capsules containing an electrically insulative material, a third layer71comprising randomly or non-randomly oriented nano-fiber composite, and a fourth layer73comprising nano-tubes or nano-capsules containing an electrically insulative liquid. When a whisker75, or other undesirable structure or material, cracks or punctures the nano-tubes or nano-capsules in the second layer69or fourth layer73, the electrically insulative liquid leaks out and is transferred from the nano-tubes or nano-capsules to the surface of the whisker75, so that the whisker75is coated with an insulative coating layer70of the electrically insulative liquid. The whisker75, or other undesirable structure or material, is rendered electrically inactive by the insulative coating layer70such that the whisker75, or other undesirable structure or material, will not cause electrical faults or short-circuits. The third layer71can cause the whisker75to be deformed, bent, redirected, or to cause the movement of the whisker75to be slowed or stopped. Thus, the third layer71can act as a physical impediment to the whisker75and is a form of mechanical mitigation preventing the whisker75from creating electrical faults. The combination of the second layer69, third layer71and fourth layer73provides added protection against electrical faults caused by the whisker75. The physical impediments of the third layer71might have the adverse effect of removing some of the insulative coating layer70from the whisker75, or the physical impediments of the third layer71might deform the whisker75such that uncoated surfaces of the whisker75have a higher likelihood of contacting another conductive material and creating an electrical fault. However, the fourth layer73provides an additional coating of the electrically insulative liquid to the whisker75and reduces the likelihood that the whisker75will create an electrical fault.

Referring toFIG. 7, a cross-sectional diagram of a nano-capsule or nano-tube according to an illustrative embodiment of the invention is shown. A nano-capsule or nano-tube wall81completely surrounds and encapsulates a liquid83such that the liquid83is not in fluid communication with any structure besides the nano-capsule or nano-tube wall81. In one embodiment, the nano-capsule or nano-tube wall81can be made of melamine-formaldehyde or some other phenolic material that is frangible or breakable at least to metallic whiskers, and the liquid83can comprise a liquid that is both electrically insulative and an adhesive, such as an electrically insulative epoxy, silicone, polyurethane, polysulfide, cyanoacrylates, or other type of adhesive. Alternatively, an embodiment of the liquid83could be some combination of a plurality of epoxy, silicon oil, and 2-ethylhexanoic acid.

Referring toFIG. 8, a cross-sectional diagram of a nano-capsule or nano-tube according to an illustrative embodiment of the invention is shown. A nano-capsule or nano-tube wall82surrounds and encapsulates a liquid84such that the liquid84is not in fluid communication with any structure besides the nano-capsule or nano-tube wall82. The liquid84contains particles85that can be adapted or selected to be registerable on a sensor instrument. For example, in one embodiment, the particles85can include visual colorant so that after the nano-capsule or nano-tube wall82has been punctured by a puncturing structure, the liquid84leaks out of the nano-capsule or nano-tube releasing the particles85and allowing the particles85to color the surrounding materials such that the presence of a puncture can be detected. In another embodiment, the particles85can include formulations that interact with another nearby material, such as a matrix material that a nano-capsule is distributed into, and the interactions can be detected, e.g., in infrared. In another embodiment, the particles85may be detectable by EM spectrum analysis, whereby the particles85comprise materials and structures that create a specific EM spectrum reaction, pattern, or fingerprint (e.g., visual, EM spectrum detector, radio-frequency identification pattern, etc.). In another embodiment, the particles85comprise some type of phosphor/fluorescent material added to liquid84. In another embodiment, the particles85can be adapted to enhance the elastic modulus of the surrounding structure when liquid84is released. Additionally, the particles85can aid in determining whether tampering or counterfeiting has occurred by providing a detectable reaction to said tampering or counterfeiting. If a piece of electronic equipment that is fitted with capsules as described above is tampered with, then the particles85will provide clear evidence of the stresses that the tampering induced. For example, in one of the described embodiments, the tampering will cause some of the capsules to rupture and release a detectable colorant.

Referring toFIG. 9, a diagram of a nano-capsule or nano-tube85being punctured by a whisker91according to an illustrative embodiment of the invention is shown. The whisker91mechanically punctures a nano-capsule or nano-tube wall89, which releases an insulative chemical87such that the whisker91is covered with a coating95of the insulative chemical87. The insulative chemical87adhesively bonds to the whisker91in such a way that the insulative chemical87can obstruct the whisker91from growing further.

Referring toFIG. 10, a diagram of an insulator chemical105binding to a whisker107according to an illustrative embodiment of the invention is shown. Nano-capsules or nano-tubes101are comprised of walls103that completely surround the insulator chemical105such that the insulator chemical105is not in fluid communication with any other object. In one embodiment of the invention, the insulator chemical105contains, for example, a 2-ethylhexanoic acid in the compound. During the formation of the whisker107, a tin oxide film109(e.g., SnO or SnO2) can form on the outside of the whisker107. After the whisker107has punctured113the wall103of the nano-capsule or nano-tube, the insulator chemical105is released and coats the whisker107. In one embodiment, the the 2-ethylhexanoic acid found in the insulator chemical105contacts the tin oxide film109, resulting in a chemical reaction111that forms stannous octoate, which can act as a catalyst and cause the adhesive elements of the insulator chemical105to cure faster. Faster curing of the insulator chemical105can create a better insulative coating around the whisker107. Accelerated curing caused by the chemical reaction111can also cause more of the surface of whisker107to be electrically inactive by helping the insulator chemical105to more fully cover and coat the whisker107.

Referring toFIG. 11, a diagram of a method of manufacture according to an illustrative embodiment of the invention is shown. Step121includes providing encapsulating structures formed to rupture or fracture in the presence of a puncturing structure and further adapted to encapsulate a liquid with insulative and adhesive qualities without chemically reacting to the liquid. Step123includes filling the encapsulating structures with a liquid that is electrically insulative and has adhesive properties. After filling the encapsulating structures with an insulator chemical, the encapsulating structures are dispersed into a matrix material, as in step125. Next, in step127, the matrix material containing the encapsulating structures is coated with some type of adhesive substance adapted to bind the matrix material to a conformal coating of a PCB. Finally, in step129, the coated matrix material is applied to the conformal coating of the PCB such that the conformal coating and the coated matrix material adhere to one another. The filling step can include injecting the encapsulating structures with liquid under pressure or including a material in the encapsulating structures which induces a pressure to expel the liquid.

Referring toFIG. 12, a diagram of a method of manufacture according to an illustrative embodiment of the invention is shown. Step131includes providing a matrix material comprising randomly oriented fibers adapted to have an elastic modulus higher than any whisker material. Step132includes providing further encapsulating structures formed to rupture or fracture in the presence of a puncturing structure and further adapted to encapsulate a liquid with insulative and adhesive properties. Step133includes filling the encapsulating structures with the liquid that is electrically insulative and adhesive. After the encapsulating structures are filled with an insulative chemical the encapsulating structures are then dispersed into the matrix material composed of randomly oriented fibers, as in step134. Next, in step135, the matrix material, now filled with encapsulating structures, is coated with some type of adhesive substance adapted to bind the matrix material to a conformal coating of a PCB. Finally, in step136, the coated matrix material is applied to the conformal coating causing the matrix material to adhere to the conformal coating.

Referring toFIG. 13, a diagram of a method of manufacture according to an illustrative embodiment of the invention is shown. Step141provides encapsulating structures formed to rupture or fracture in the presence of a puncturing structure and further adapted to encapsulate a liquid with insulative and adhesive properties. Next, in step143, the encapsulating structures are filled with a liquid having both electrically insulative and adhesive properties. After filling the encapsulating structures with an insulator chemical, the encapsulating structures are dispersed into a first matrix material, as in step145. Next, in step147, the first matrix material containing encapsulating structures is coated with some type of adhesive substance adapted to bind the first matrix material to a conformal coating of a PCB. In step149, the coated first matrix material is applied to the conformal coating causing the first matrix material to bond to the conformal coating. A second matrix material is provided in step151. The second matrix material is then mixed with a randomly oriented fiber such that the resulting material has an elastic modulus higher than tin or any other type of whisker material, as in step153. Next, in step155, the second matrix material containing randomly oriented fibers is coated with some type of adhesive substance adapted to adhere to a coated matrix material containing encapsulating structures. Finally, in step157, the coated second matrix material is applied to the coated first matrix material containing encapsulating structures such that the first matrix material adheres to the second matrix material.

In another exemplary embodiment, micro-tubes, micro-structures, or micro-capsules can be used instead of nano-tubes, nano-structures, or nano-capsules to encapsulate the insulative liquid, perform functions such as those described herein, or produce effects such as described associated with nano-scale structures described herein.

In another exemplary embodiment, the encapsulating structures, e.g., nano-capsules or nano-tubes, are provided with scribe lines or structural elements that result in a predetermined rupture or fracture in the encapsulating structure, allowing the insulative liquid contained therein to be transferred to specific locations or orientations relative to the encapsulating structure. For example, a selected portion of a wall of the encapsulating structure can be etched to form a weaker area of the encapsulating structure that is more susceptible to rupture or fracture, and thus ensure liquid is expelled in a particular direction or towards a specific location to which an intrusive structure poses a greater danger.

In another exemplary embodiment, the conformal coating comprises a tin finish or a solder coating and the layers and matrix material described above is adapted to adhere to a tin finish or solder coating.

Another exemplary embodiment can add or include a step of coating with or applying to the structures described herein (e.g., micro- or nano-tubes or micro- or nano-capsules containing insulative and adhesive liquid) some type of adhesive substance adapted to bind the structures to the conformal coating on the PCB.

An exemplary embodiment could also include use of a chemical or liquid in the tubes that can be injected into the tubes or containment structure under pressure to facilitate coating action of the chemical on the intrusive or undesirable structure. Note that a variety of embodiments of the invention can be created including alternative structures which contain the a suitable liquid or chemical which are in a structure besides a tube (e.g., box or laminate encapsulating structure), but perform the same or similar functions and provide similar multiple effects as a tube described herein e.g., multi-intrusion vector diversion, selective action, capture effects, insulator coating, capture effect, accelerant effect, etc. to name some of such effects For example, an exemplary liquid or chemical in accordance with one embodiment of the invention can also be formed within laminated or multi-walled containment structures, e.g., tubes, which have additional chemical or liquids which facilitate coating of the intrusive structures such as a material which accelerates drying or persistent coating of such intrusive structures e.g., tin whiskers.