Packaging techniques for electronic devices

One disclosed method includes defining an electrical trace on a first substrate; physically coupling an electronic component to the first substrate, wherein a portion of the electrical trace completely encircles the electronic component; overlaying a second substrate onto the first substrate, the overlaying causing the second substrate to completely cover the portion of the electrical trace and the electronic component; electrically coupling an electrical power source to the electrical trace to generate a current in the electrical trace; melting the second substrate using heat generated by the current through the electrical trace; and fusing the second substrate to the first substrate to generate a hermetic seal around the electronic component.

FIELD

The present application generally relates to packaging techniques, and more specifically relates to packaging techniques for electronic devices.

BACKGROUND

Biosensors may be used over an extended period of time, e.g., days, weeks, or months, and may be used to obtain physiological information about the wearer. For example, invasive biosensors may be used to obtain analyte information from interstitial fluid. Non-invasive biosensors may be used to obtain information relating to cardiac activity or blood flow. Similarly, biostimulators may be used to apply stimuli to a wearer and may be implanted within the wearer. Such biosensors and biostimulators may include sensitive electronics that may be damaged or destroyed if contaminants, such as bodily fluid, enter the device's housing and come into contact with the electronics.

SUMMARY

Various examples are described for packaging techniques for electronic devices. One disclosed method includes defining an electrical trace on a first substrate; physically coupling an electronic component to the first substrate, wherein a portion of the electrical trace completely encircles the electronic component; overlaying a second substrate onto the first substrate, the overlaying causing the second substrate to completely cover the portion of the electrical trace and the electronic component; electrically coupling an electrical power source to the electrical trace to generate a current in the electrical trace; melting the second substrate using heat generated by the current through the electrical trace; and fusing the second substrate to the first substrate to generate a hermetic seal around the electronic component.

Another disclosed method includes defining an electrical trace on a first substrate; creating a plurality of electronic devices on the first substrate, each electronic device comprising an electronic component, each electronic device created on a separate portion of the first substrate, wherein the electrical trace defines boundaries between each electronic device; electrically coupling an electrical power source to the electrical trace to generate a current in the electrical trace; and melting the first substrate using heat generated by the current through the electrical trace to singulate each electronic device of the plurality of electronic devices.

A further disclosed method includes forming a self-assembled mask on a substrate, the self-assembled mask comprising a mask substance and defining a plurality of gaps; applying a first etching substance to the substrate to etch the substrate at locations corresponding to the plurality of gaps, the first etching substance configured to etch the substrate and to not react with the mask substance; and applying a second etching substance to the self-assembled mask to remove the self-assembled mask from the substrate, the second etching substance configured to etch the self-assembled mask but to not react with the substrate.

These illustrative examples are mentioned not to limit or define the scope of this disclosure, but rather to provide examples to aid understanding thereof. Illustrative examples are discussed in the Detailed Description, which provides further description. Advantages offered by various examples may be further understood by examining this specification.

DETAILED DESCRIPTION

Examples are described herein in the context of packaging techniques for electronic devices. Those of ordinary skill in the art will realize that the following description is illustrative only and is not intended to be in any way limiting. Reference will now be made in detail to implementations of examples as illustrated in the accompanying drawings. The same reference indicators will be used throughout the drawings and the following description to refer to the same or like items.

Electronic devices, including biosensors and biostimulators to be worn or implanted within a wearer, may be susceptible to damage if fluids or other contaminants are able to penetrate the device and come into contact with its electronics. This may be generally true for any electronic device, though some environments, such as within the human body, may present significant risk for such contamination and damage. Thus, it can be desirable to hermetically seal electronics within a package to reduce the chances of contaminants reaching the electronics, or at least to slow their progress.

In one illustrative example according for packaging techniques for electronic devices, an electronics device may be constructed on a substrate, such as a printed circuit board (“PCB”) material, e.g., a polyimide or FR-4 material. In addition to electronic components affixed to or deposited on the PCB, an electrical trace may be deposited on the PCB and routed to entirely surround, or encircle, the electronic components within the electrical trace. For example, the electrical trace may be routed around the PCB just inside of its perimeter edge. The electrical trace may be connected to two electrical contacts, each contacting one end of the electrical trace. Such an arrangement may create a resistive heating element, also referred to as a microheater, so that when a voltage is applied across the two contacts, electrical current runs through the electrical trace, heating it.

After the electronic components and electrical trace have been affixed to the PCB, a layer of a liquid crystal polymer (“LCP”) substrate is overlaid on the electronics and electrical trace, completely covering them. In this example, pressure is applied to the LCP substrate to hold it in place, though pressure is not required. A power source is then connected to the two electrical contacts and current is flowed through the electrical trace, as described above. The electrical trace outputs heat, which is absorbed by the PCB and the LCP substrate. Sufficient heat is output to melt the LCP substrate into contact with the PCB. After the LCP has melted sufficiently, the power source is disconnected from the electrical contacts and the LCP solidifies and fuses with the PCB, creating a hermetic seal around the electronic components.

Such a technique may allow the use of an LCP substrate, which has a relatively high melting point, e.g., greater than 250 degrees Celsius, but provides high quality hermetic seals, in contexts where applying such high temperatures to the entire PCB and electronic components may damage or destroy them. For example, simply overlaying the LCP substrate on the PCB and heating the entire structure to the LCP substrate's melting point would melt the LCP substrate, but would also subject the PCB and electronic components to the same high temperatures. Instead, the use of the electrical trace as a microheater provides precise heating only where the heat is needed to melt and fuse the LCP substrate to the PCB, away from otherwise sensitive electronic devices. Further, such a technique directly melts the LCP substrate to create the hermetic seal, rather than melting another bonding agent, such as a solder or epoxy, to seal the substrate layers together. Use of such an intermediate bonding agent may couple the LCP substrate to the PCB, but may not provide a strong, hermetic seal around the entirety of the electronics device. Thus, the illustrative example provides a high-quality hermetic seal by directly heating and melting the LCP substrate cover to the PCB substrate.

In addition to creating a hermetic seal, microheaters may be used to singulate individual electronic devices formed on a common substrate, such as a PCB material. For example, multiple electronic devices, e.g., multiple biosensors or biostimulators, may be constructed on a common sheet of substrate. An electrical trace (or multiple electrical traces) may then be formed along the desired perimeters of each biosensor or biostimulator and connected to two electrical contacts, as discussed above. A power source may then be coupled to the electrical contacts to flow current through the electrical trace, thereby heating and cutting the sheet of substrate and singulating the individual electronic devices from each other. Such a technique may also be combined with the hermetic sealing technique discussed above, such as by using one electrical trace to seal the electronics, and a second electrical trace to singulate the devices.

Using electrical traces as microheaters may provide manufacturing advantages over other singulation techniques, such as mechanically cutting, e.g., sawing, the substrate or by using a laser to cut the substrate. Such techniques may be expensive or create significant amounts of debris, which is a potential contaminant.

In addition, in some examples, LCP substrate materials, such as discussed above, may have one or more thin films applied to them during manufacturing, such as to provide biocompatibility or an adhesive to mount a biosensor to a wearer's skin. Further, thin films could be metal traces or contacts used for electrical routing and connection of electronic components, electrodes, etc. In some examples, thin films could include non-metals to create fluidic channels, smooth topographies, or another protective layer.

However, because LCP substrates can be very smooth, obtaining a robust bond with a thin film may be difficult. Thus, in this illustrative example, before the LCP substrate is overlaid on the electronic device to create a hermetic seal, it is processed to roughen the surface to provide enhanced bonding or adhesion characteristics. In this example, a self-assembled mask is grown on a sheet of LCP substrate to the point where the mask partially, but does not completely, forms a film on the surface of the LCP substrate. The partially-masked LCP substrate is then etched using a wet or dry chemical etch to create cavities in locations not covered by the mask. The mask is then removed, leaving the LCP substrate with a partially etched, rough surface that may be suitable to bond thin films to it.

Such a technique may be advantageous over other techniques, such as a maskless wet etching process or heat-emboss molding. Such a maskless etch technique may provide only limited roughening of the LCP substrate, which may be of little to no benefit in applying a thin film. Further, the heat-emboss molding involves heating the LCP substrate until it softens, and then imprinting it with one or more molds with roughening features on them. As discussed above, applying significant heat to the LCP substrate may damage electronics in the underlying device, or it may only allow limited roughness characteristics based on the selected mold(s).

Thus, techniques according to this disclosure may provide packaging techniques to seal and singulate electronic devices, as well as apply thin film layers within or onto the sealed devices. This illustrative example is given to introduce the reader to the general subject matter discussed herein and the disclosure is not limited to this example. The following sections describe various additional non-limiting examples of packaging techniques for electronic devices.

Referring now toFIG. 1,FIG. 1shows an example electronic device100. In this example, the electronic device100is formed on a substrate110, such as a PCB material, which has multiple electronic components120a-ephysically coupled to it. And while the substrate110is PCB in this example, any suitable substrate material may be employed, including LCP material, soft organic films, plastics, polymers (e.g., polyether ether ketone (“PEEK”)), low-melting-point glass sheets or metal foils, etc. The electronic components120a-emay include any suitable electronics components, including electronic chips, e.g., microprocessors, microcontrollers, application-specific integrated circuits (“ASICs”), etc.; transistors; resistors; capacitors; inductors; diodes; etc. Further, while the example device100includes five electronic components120a-e, any suitable number of electronic components may be employed.

Such an electronic device100may be used for any suitable purpose, including in a biosensor or biostimulator. Biosensors include devices that include one or more sensors to sense physiological information about a wearer, such as pulse rate, blood pressure, SpO2 or SvO2, glucose level, lactate level, etc., including drawing blood samples, etc. Biostimulators include devices that can provide physiological stimulus to the wearer, such as by applying voltage or current to nerves or organs, inject materials into the wearer's body, etc.

A biosensor or biostimulator device may be wearable, invasive, or implantable. A wearable device may be an electronic device that can be worn on a wearer's body, such as a watch, a contact lens, a chest strap, an arm band, a wristband, eyeglasses, an earring, etc. Such devices may be worn against the surface of the wearer's skin, or may include one or more invasive components. An invasive device includes components that are inserted beneath the wearer's skin, but where a portion of the device remains outside of the wearer's skin. For example, a continuous glucose monitor (“CGM”) may include a sensor wire that is inserted into the wearer's skin to contact the interstitial fluid beneath the surface of the skin, while also including a component that is affixed to the wearer's skin, such as by an adhesive. Implantable devices include devices that are entirely implanted beneath a wearer's skin, within an internal cavity, or attached to an organ of the wearer's body, such as the brain or one or more nerve bundles. It should be appreciated that an implanted device may be connected to another device that has not been implanted, such as via a wired or wireless communication connection.

Further, it should be appreciated that this disclosure is not limited to biosensors or biostimulators. Rather, the techniques described herein may be used in any suitable context that includes packaging electronic devices. Such electronic devices may include any kinds of electronic components, including those discussed above. Further, electronic device may also include mechanical components, such as motors, piezoelectric elements, etc.; optical components, such as lenses, optical filters, etc; etc. Thus, electronic devices broadly include any system that includes such components. Thus, while examples discussed herein may include example biosensors or biostimulators, other types of electronic devices fall within the scope of the present disclosure.

Referring now toFIG. 2A,FIG. 2Ashows an example electronic device200formed on a substrate210, such as a PCB material. The electronic device200includes multiple electronic components220a-e, generally as described above with respect toFIG. 1. In addition, an electrical trace230has been formed on the substrate210and entirely encircles each of the electronic components230a-c. An electronic component230a-eis encircled if there are no gaps in the electrical trace230running the perimeter of the electronic component. In this example, each of the electronic components230a-eis individually encircled; however, the electrical trace230, in some examples, may collectively encircle all of the electronic components230a-ewithout individually encircling each. In some examples, some of the electronic components230a-emay be individually encircled, while others may be collectively encircled. Further, in some examples, one or more electronic components230a-emay be individual encircled, and it may further be collectively encircled along with one or more other electronic components230a-e.

In addition, the electrical trace230is electrically coupled to two electrical contacts232a-b. The electrical contacts232a-bmay be used to connect the electrical trace230to a power supply. When connected to a power supply, the power supply may supply a voltage across the electrical contacts232a-bthereby generating a current in the electrical trace230. The electrical resistance of the electrical trace330to the current generates heat, which may be used to melt and fuse a piece of another substrate material to substrate210to seal the electronic components230a-e.

Further, in some examples, the electrical trace230may be formed as a coil encircling the electronic components230a-e, such as may be seen inFIG. 2B. In this example, the electrical trace232is formed in a coil to provide wireless inductive coupling with a power source. Thus, separate electrical contacts, such as shown inFIG. 2A, may be omitted, and the electrical coupling with the power source may be wireless.

Referring now toFIG. 3,FIG. 3shows a cross-section of an example electronic device300according to this disclosure. The electronic device300includes device electronics302that have been physically coupled to a substrate310, such as PCB material. An electrical trace330has been formed on the substrate310and encircles the device electronics302, generally as described above with respect toFIGS. 2A-2B.

In this example, a second substrate320has been overlaid on top of the device electronics302, the electrical trace330, and substrate310. In this example, the second substrate320includes a sheet of LCP material; however, any suitable substrate material may be employed according to different examples, such as soft organic films, plastics, low-melting-point glass sheets or metal foils, etc. After the second substrate320has been overlaid, a power source is electrically connected to the electrical trace330to generate a current in the electrical trace330. The current generates heat332based on the electrical resistance of the electrical trace330, which is transmitted to both substrates310,320. In this example, the power source provides sufficient current to heat and melt the second substrate320, but not the first substrate310. Thus, the heat output by the electrical trace330melts the second substrate320. In some examples, external pressure may be applied to part or all of the second substrate320to press the second substrate320against substrate310and the electrical trace330to assist with the sealing process; though in some examples, no external pressure is applied.

After the second substrate320has melted along the length of the electrical trace330encircling the device electronics302, the power source is disconnected and the melted substrate is allowed to cool and solidify, thereby bonding to substrate310and sealing the device electronics302between the second substrate320and substrate310. In this example, the sealing process creates a hermetic seal around the device electronics302. As discussed above, the seal is created by melting the second substrate. No additional bonding agent, such as an epoxy or solder, is employed to create seal between substrate310and the second substrate320. Thus, by melting the substrate without the use of another bonding agent, a hermetic seal is created between the substrate310and the second substrate320.

While in this example, the electrical trace was formed on substrate310, in some examples, in may be formed on substrate320instead. Thus, the electrical trace330, or portions of the electrical trace330, may be formed on a separate substrate than the device electronics302. Further, as discussed above with respect toFIG. 2B, the electrical trace330may be formed as a coil encircling the device electronics302. Thus, separate electrical contacts may be omitted, and the electrical coupling with the power source may be wireless.

Referring now toFIGS. 4A-4B,FIG. 4Ashows a top-down view of an electronic device400according to this disclosure, whileFIG. 4Bshows a cross-section of the example electronic device400. The electronic device400ofFIGS. 4A-4Bgenerally includes the same components as the electronic device300described above with respect toFIG. 3. It includes device electronics402affixed to a substrate410. An electrical trace430a-bis formed on the substrate410and encircles the device electronics and is electrically coupled to two electrical contacts (not shown). In addition, a desiccant440is also disposed on the substrate440and encircles the device electronics402. In this example, the desiccant440encircles the device electronics402outside of, but concentrically with, a first portion430aof the electrical trace430a-b, and inside of a second portion430bof the electrical trace430a-b. In this example, the electrical trace430a-bis a single contiguous electrical trace; however, in some examples, the first portion430aof the electrical trace430a-bmay be separate from the second portion430bof the electrical trace430b. In one such example, each separate electrical trace may be electrically coupled to a separate pair of electrical contacts; however, in some examples, some or all of the separate electrical traces may share the same pair of electrical contacts.

Similar to the example shown inFIG. 3, a second substrate420is overlaid on top of the device electronics402, the electrical trace430a-b, and the desiccant440. In this example, the second substrate420is an LCP substrate; however, any suitable substrate material may be employed according to different examples. After the second substrate420has been positioned, a power source is electrically coupled to the electrical trace430a-band transmits a current through the electrical trace430a-b. The current generates heat432via the electrical trace's electrical resistance generally as described above, which melts the second substrate420. After the second substrate420has been sufficiently melted, the power source is disconnected, which allows the second substrate420to cool and bond to substrate410creating a seal between the two substrates410,420. In this example, because the device electronics402are encircled by the electrical trace430a-b, a hermetic seal is created. Further, the desiccant440is also hermetically sealed between the two substrates410,420, and can provide further resistance to encroachment of contaminants if the heat-seal were to be compromised. As discussed above, no additional bonding agent, such as an epoxy or solder, is employed to create seal between substrate410and the second substrate420. Thus, by melting the substrate without the use of another bonding agent, a hermetic seal is created between the substrate410and the second substrate420.

Further, while in this example, the electrical trace430a-bwas formed on substrate410, in some examples, in may be formed on substrate420instead. Thus, the electrical trace430a-b, or portions of the electrical trace430a-b, may be formed on a separate substrate than the device electronics402. Further, as discussed above with respect toFIG. 2B, the electrical trace430a-bmay be formed as a coil encircling the device electronics402. Thus, separate electrical contacts may be omitted, and the electrical coupling with the power source may be wireless.

Referring now toFIG. 5,FIG. 5shows an example method500according to this disclosure. The description ofFIG. 5will be made with respect to the example device300shown inFIG. 3, though any suitable device or arrangement may be employed.

At block510, an electrical trace330is defined on a first substrate310. Any suitable conductive material may be employed, such as copper, aluminum, etc., to define the electrical trace330. The electrical trace330is formed to encircle locations where one or more electrical components will be positioned on the first substrate310. In some examples, the electrical trace330will individually encircle one or more electronic components, while in some examples, the electrical trace330will collectively encircle some or all of the electronic components, or both individually encircle one or more electronic components and collectively encircle some or all of the electronic components. In this example, the electrical trace is electrically coupled to two electrical contacts formed on the first substrate310. The electrical contacts may be formed at block510or at any suitable time during the manufacturing process, such as at block530. Further, while in this example, the electrical trace330is formed on the first substrate, in some examples, it may be formed on the second substrate320instead. Thus, electronic components302may be physically coupled to the first substrate310, while the electrical trace330may be applied to the second substrate.320

At block520, one or more electronic components, illustrated as the device electronics302, are physically coupled to the first substrate310. Any suitable electronic components may be employed according to different examples and device designs. It should be appreciated that while block520follows block510in this example, block520may precede block510in some examples, or they may be performed at substantially the same time.

At block530, a second substrate320is overlaid on the first substrate310and on top of the device electronics302and the electrical trace330. In this example, the second substrate is an LCP substrate and is overlaid to completely cover the device electronics302and the electrical trace330; however, in some examples, the second substrate330may only cover a portion of the device electronics302. For example, a portion of the device electronics302may be designed to operate in an environment having various contaminants, e.g., a sensor. In one such example, such portion of the device electronics302may not be covered by the second substrate320.

At block540, a power supply is coupled to the electrical trace330. In this example, the power source is electrically coupled to the electrical contacts to supply a voltage across the contacts and to supply a current to the electrical trace330. In some examples, however, the power source may be coupled to any two points on the electrical trace330so long as current traverses the entire electrical trace encircling the device electronics302.

At block550, the current supplied by the power source causes the electrical trace330to generate heat, which melts the second substrate320at locations corresponding to the electrical trace330. In this example, the heat generated by the electrical trace330is sufficient to melt the second substrate320, but not the first substrate310. Though in some examples the heat may be sufficient to melt both substrates310,320.

At block560, the second substrate320is fused to the first substrate310. In this example, the power source stops supplying current to the electrical trace330, which allows the electrical trace330and the substrates310-320to cool, thereby allowing the second substrate320to solidify and fuse with the first substrate310. In examples where both substrates310,320melt, both cool and fuse to each other.

Referring now toFIG. 6,FIG. 6shows an example substrate600having multiple electronic devices300formed on it. For example, a single PCB may have multiple copies of the same (or different) electronic devices formed on it. The PCB may then be cut to singulate the individual electronic devices. In this example, the electronic devices300have been formed in a grid pattern and an electrical trace610forming boundaries between the discrete electronic devices300has been formed on the substrate600as well. The electrical trace610is electrically coupled to two electrical contacts612a-bto enable a power source to electrically couple to the electrical trace610. In this example, the electrical trace610is formed to enable cutting of the substrate600to singulate the individual electronic devices300. Thus, when a power source is electrically coupled to the electrical contacts612a-band supplies sufficient electrical current, the electrical trace610generates and outputs heat to the substrate600, melting or otherwise cutting substrate material away to singulate the devices300.

In some examples, the electronic devices300also include one or more electrical traces described above with respect toFIGS. 2A-5to enable hermetic sealing of the devices300with a second substrate material (not shown). Further, such hermetic sealing may occur prior to singulation of the electronic devices300. For example, the electronic devices300may be formed as described above with respect toFIG. 5. Subsequently, a power source may be electrically coupled to the electrical contacts612a-bto supply current to the electrical trace610. The heat generated by the electrical trace610may cut both the substrate600and the second substrate, thereby singulating the device300.

Referring now toFIG. 7,FIG. 7shows an example method700according to this disclosure. The description ofFIG. 7will be made with respect to the example substrate600shown inFIG. 6, though any suitable device or arrangement may be employed.

At block710, an electrical trace610is formed on a first substrate600. In this example, the first substrate is a PCB material; however, any suitable substrate may be employed. In this example, the electrical trace610is shaped to define perimeters for a plurality of electronic devices formed, or to be formed, on the first substrate600. It should be appreciated that while a single contiguous electrical trace610is employed in this example, in some examples, multiple electrical traces may be employed to define perimeters for one or more electronic devices formed, or to be formed, on the first substrate600. In this example, the electrical trace610is electrically coupled to two electrical contacts612a-bformed on the first substrate600. The electrical contacts612a-bmay be formed at block710or at any suitable time during the manufacturing process.

At block720, a plurality of electronic devices300are created on the substrate600within the perimeters defined by the electrical trace610. Each electronic device300is formed generally as described above with respect to block520of the method ofFIG. 5. It should be appreciated that while block710precedes block720in this example, in some examples, block720may be performed before block710, or they may be performed at substantially the same time.

At block730, a power supply is coupled to the electrical trace610. In this example, the power source is electrically coupled to the electrical contacts612a-bto supply a voltage across the contacts612a-band to supply a current to the electrical trace610. In some examples, however, the power source may be coupled to any two points on the electrical trace so long as current traverses the electrical trace610. Further, in some examples, the electrical trace may be formed in a coil shape to enable wireless inductive coupling with a power source. In such examples, a physical electrical coupling may not be required, and instead, the power source may be electrically coupled using wireless inductive coupling.

At block740, heat generated by the current flowing through the electrical trace610melts the first substrate600. In this example, the heat melts the PCB or other suitable substrate material, thereby singulating the electronic devices300.

It should be appreciated that the method700shown inFIG. 7may be performed in conjunction with other example methods according to this disclosure, such as example methods according to the method500ofFIG. 5. Such a method may be performed at any time before, during, or after the method700ofFIG. 7is performed. For example, the method500ofFIG. 5may be performed at block720.

Referring now toFIGS. 8A-8B,FIG. 8Aillustrates an example packaging technique for fluids within fluid cavities. In this example, a suitable substrate810has been supplied and formed with multiple fluid cavities802a, in this example, eight fluid cavities have been formed. On the substrate810, electrical traces830have been defined to encircle each of the fluid cavities and to terminate at two electrical contacts812a-b, which are also formed on the substrate810. Subsequently, a fluid804ahas been dispensed in each of the fluid cavities802a. It should be appreciated that the same fluid or other material need not be dispensed into each cavity802a. Rather, any combination of suitable fluids or other materials may be dispensed into the cavities as needed.

Referring toFIG. 8B, to seal the fluid804awithin the cavities802a, a second substrate820, such as an LCP material, is laid overtop of substrate810and the respective cavities802a. After the second substrate820has been positioned, the electrical contacts812a-bare connected to a power source (not shown), and electrical current flows through the electrical trace830, it heats and melts the second substrate820to the first substrate810, thereby sealing the fluid within the fluid cavity.

While this example illustrates the use of a fluid stored within the fluid cavity802a, it should be appreciated that other materials may be stored in such cavities, such as pills or capsules, powders, slurries, etc.

Referring toFIG. 9,FIG. 9shows an example method900according to this disclosure. In this example, the method900will be described with respect to the example shown inFIGS. 8A-8B; however it should be appreciated that other examples according to this disclosure may be employed as well.

At block910, one or more fluid cavities is defined within a first substrate810. For example, the substrate may be created with defined fluid cavities. Alternatively, the cavities may be formed in the substrate810by heating it and using a vacuum or a mold.

In some examples, it should be appreciated that block910may simply involve obtaining or otherwise providing a substrate810with one or more cavities defined in it.

At block920, an electrical trace830is defined on the first substrate810generally as discussed above with respect to block510ofFIG. 5.

At block930, a fluid or other substance is placed within one or more of the cavities. For example, an aqueous solution, a pill or capsule, a powder, etc. may be placed in one or more of the cavities.

At block940, a second substrate820is overlaid on the first substrate generally as discussed above with respect to block530ofFIG. 5.

At block950, a power supply is coupled to the electrical trace830generally as described above with respect to block540ofFIG. 5.

At block960, the second substrate820is melted generally as described above with respect to block550ofFIG. 5.

At block970, the second substrate820is fused to the first substrate810generally as discussed above with respect to block560ofFIG. 5.

Referring now toFIGS. 10A-10D,FIGS. 10A-10Dshow an example packaging technique for biosensors and biostimulators. In this example, a self-assembled mask is formed on a surface of a substrate1000, such as a second substrate320,420shown inFIGS. 3 and 4. Any suitable substrate material, such as LCP or PEEK (e.g., in a flexible configuration), or rigid substrates, such as glass or quartz, may be employed according to this example.FIGS. 10A-Dillustrates different stages of creating self-assembling masks1020a-d. In this example, a masking material1010is deposited, such as by thermal evaporation or sputtering, on the substrate1000over time to build up a mask1020a-d. In some examples, a suitable thickness of the deposited masking material is between substantially 5 and 40 nanometers (“nm”), inclusive. Suitable masking materials include aluminum, copper, gold, chromium, etc.

Over time, as more masking material1010is deposited, the mask1020ainitially includes individually dispersed clusters of masking material1010, followed by joining of clusters to create a mask1020bhaving islands of masking material1010. The islands of masking material may further accumulate additional masking material1010and join to create links between different islands of masking material to create a further mask1020c. Finally, sufficient masking material is deposited to form a continuous film mask1020dover the entire portion of substrate. According to this disclosure, any of self-assembled masks1020a-cmay be employed, referred to as masks1020a-cthat define a plurality of gaps; however, the continuous film mask1020dmay not be suitable. Though as discussed below with respect toFIGS. 15A-15B, thermal heating to create a discontinuous self-assembled mask may be employed even in scenarios where a continuous film mask is deposited on the substrate.

In this example, after the masking material has been deposited, the substrate with the deposited masking material is heated to help bond the masking material to the substrate. Suitable temperatures and heat times for such a process are based on the metal material that is used, the substrate material, and the activation energy between the substrate and the masking material. In addition, the thickness of the initial masking layer may help adjust the heat-soak times; however, temperatures between approximately 100-350 degrees Celsius with heat-soak times between approximately ten minutes to three hours may be sufficient for most substrate-mask combinations. Further, depending on the substrate, an activation energy may be modified, such as by using a chemical treatment, including oxidizing the substrate (e.g., oxidizing a silicon substrate), nitrogenize the substrate (e.g., nitrogenizing a silicon (Si) substrate to form a thin Si3N4layer), reacting the substrate with hexamethyldisilazane (“HMDS”), etc.

Such a heat-soak process can also advantageously cause the deposited masking material to coalesce into discrete particles. This can help provide a randomized discontinuous mask layer on the substrate, even if the initial deposition resulted in a significant portion of the substrate being covered by the masking material. An example of this can be seen inFIGS. 15A-15B.

FIG. 15Aillustrates deposited mask material on a substrate after different deposition times1510a-d. As can be seen, in image1510a, nanoparticles of a silver mask material have a size of approximately 12 nm with substantial gaps visible between the particles. The particle sizes grow until adjacent particles join together, until ultimately only a few small gaps are visible in image1510d.

FIG. 15Billustrates the same mask layers shown inFIG. 15A; however, the mask layers inFIG. 15Bhave been heat-soaked at 190 degrees Celsius for 50 minutes. As can be seen, the particles in each mask layer have coalesced into discrete particles, providing a discontinuous mask layer on the underlying substrate. Such an effect is visible even in image1520d, which is the resulting mask layer following a heat-soak of the mask layer shown in image1510d. Thus, a continuous, or nearly continuous, thin film of mask material may still be rendered into a suitable discontinuous mask layer via a thermal soak process.

Referring now toFIGS. 11A-11C,FIGS. 11A-11Cillustrate the use of self-assembling masks to create surface roughness on a substrate.FIG. 11Ashows a cross-section of a substrate1100, such as an LCP substrate material, having a self-assembled mask formed on its surface from a masking material1110. The self-assembled mask may be any suitable self-assembled mask that defines a plurality of gaps to expose the underlying substrate1100, such as the masks1020a-cshown inFIGS. 10A-10C.

FIG. 11Bshows the substrate1100after an etching material has been applied to the substrate. The etching material in this example is configured to etch the substrate1100while not affecting the masking material1110. Suitable etching materials include wet chemicals, such as acids, or dry plasma using reactive gases. Thus, the etching material forms cavities1120in the substrate at locations not covered by the masking material1110.

FIG. 11Cshows the substrate1100after a second etching material has been applied to the substrate1100and masking material1110. The second etching material is configured to etch the masking material1110but not the substrate1100. Thus, atFIG. 11C, the substrate1100has been pitted by the etching material, while other portions of the substrate1100remain unaffected. The substrate1100defining the cavities1120may then have a rough surface to enable better bonding or adhesion with other substances, such as one or more thin films. In some examples, thin films could be metal traces or contacts used for electrical routing or connection of electronic components, electrodes, etc. In some examples, thin films could include non-metals to create fluidic channels, smooth topographies, or another protective layer

Referring now toFIG. 12,FIG. 12shows an example method1200according to this disclosure. The method1200will be described with respect toFIGS. 10 and 11, though any suitable examples according to this disclosure may be employed.

At block1210, a self-assembled mask1020a-cdefining a plurality of gaps is formed on a substrate material1000. In this example, the self-assembled mask1020a-cis formed by thermal evaporation of a suitable masking material1010, such as aluminum, copper, chromium, gold, etc. Any suitable self-assembled mask1020a-cmay be employed; however, a continuous film mask1020dcovering the entire substrate may be unsuitable. Further, while evaporation of the masking material1010is employed in this example, in some examples, sputtering of the material may be employed instead. In this example, masking material1010is applied to the substrate1000to create a mask having a thickness of between substantially 5 nm to 40 nm, inclusive. Though any suitable thickness may be employed

At block1220, a first etching material is applied to the substrate1000,1100and self-assembled mask1020. In this example, the first etching material is configured to form one or more cavities1120in the substrate1000,1100, such as may be seen inFIG. 11B. In this example, the first etching material is a dry-plasma etch. However, it should be appreciated that suitable chemicals may be employed to perform a wet chemical etch in the substrate1000.

At block1230, after one or more cavities have been formed in the substrate1000,1100, the self-assembled mask is removed by using a second etching material configured to etch the masking material1010,1110, but not the substrate1000,1100. Suitable second etching materials include wet chemicals, such as acids. For example, if the masking material is aluminum, the second etching material may include phosphoric acid. It should be appreciated that block1230may be omitted in some examples.

For example, referring toFIG. 13,FIG. 13shows a table having experimental results using an aluminum masking material deposited on a substrate. As is shown, the test results indicate whether the aluminum mask layer was kept or removed, and further indicate the thickness of the aluminum mask layer for each test. After the aluminum mask was applied and the underlying substrate was etched (using a dry-plasma etch), the surface roughness was quantified using two techniques, Sa and Sq. For several of the tests, the aluminum mask layer was removed before the surface roughness was quantified. In general, the larger the Sa or Sq value, the rougher the surface. Thus, in the case where the aluminum mask was kept, a 15 nm mask layer provided the greatest effect roughness (Sa value of 1.78), while an initial aluminum mask layer of 20 nm provided the greatest effective roughness (Sq value of 1.62) value when the mask layer was removed. Though it should be appreciated that both the Sa and Sq values may be considered together to determine the proper mask height and whether to remove the mask or not. However, surface roughness was increased in each test, and a suitable level of roughness may be obtained even if different mask depths are used or even if the mask layer is removed.

FIG. 14provides further indication of the surface roughness based on the etch time for each respective mask thickness (showing both Sa and Sq curves). In particular, as can be seen, by approximately 8 minutes, little to no additional increase in surface roughness was achieved.

Referring again toFIG. 12, at block1230, in some examples, leaving the masking material may provide other advantages, including increased structural integrity or enhanced material properties. For example, the mask may also provide an adhesion layer for other materials, such as gold or other noble metals.

At block1240, after the self-assembled mask has been removed, a thin film may be applied to the etched substrate. The formation of the cavities1120on the substrate1110may roughen the surface of the substrate1110to provide a better bonding or adhesion surface for the thin film material.

It should be appreciated that the method1200ofFIG. 12may be performed in conjunction with one or more other methods500,700according to this disclosure. For example, the method1200ofFIG. 12may be performed at block720of the method700shown inFIG. 7, or after block560of the method500shown inFIG. 5; however, any suitable time during such methods may be employed.

Some of the methods described herein may be performed by robotic manufacturing components controlled by software executed by a processor or may be implemented as specifically-configured hardware, such as field-programmable gate array (FPGA) specifically to execute the various methods. For example, examples can be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in a combination thereof. In one example, a device may include a processor or processors. The processor comprises a computer-readable medium, such as a random access memory (RAM) coupled to the processor. The processor executes computer-executable program instructions stored in memory, such as executing one or more computer programs. Such processors may comprise a microprocessor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), field programmable gate arrays (FPGAs), and state machines. Such processors may further comprise programmable electronic devices such as PLCs, programmable interrupt controllers (PICs), programmable logic devices (PLDs), programmable read-only memories (PROMs), electronically programmable read-only memories (EPROMs or EEPROMs), or other similar devices.

Such processors may comprise, or may be in communication with, media, for example computer-readable storage media, that may store instructions that, when executed by the processor, can cause the processor to perform the steps described herein as carried out, or assisted, by a processor. Examples of computer-readable media may include, but are not limited to, an electronic, optical, magnetic, or other storage device capable of providing a processor, such as the processor in a web server, with computer-readable instructions. Other examples of media comprise, but are not limited to, a floppy disk, CD-ROM, magnetic disk, memory chip, ROM, RAM, ASIC, configured processor, all optical media, all magnetic tape or other magnetic media, or any other medium from which a computer processor can read. The processor, and the processing, described may be in one or more structures, and may be dispersed through one or more structures. The processor may comprise code for carrying out one or more of the methods (or parts of methods) described herein.