An example sensor interposer employing castellated through-vias formed in a PCB includes a planar substrate defining a plurality of castellated through-vias; a first electrical contact formed on the planar substrate and electrically coupled to a first castellated through-via; a second electrical contact formed on the planar substrate and electrically coupled to a second castellated through-via, the second castellated through-via electrically isolated from the first castellated through-via; and a guard trace formed on the planar substrate, the guard trace having a first portion formed on a first surface of the planar substrate and electrically coupling a third castellated through-via to a fourth castellated through-via, the guard trace having a second portion formed on a second surface of the planar substrate and electrically coupling the third castellated through-via to the fourth castellated through-via, the guard trace formed between the first and second electrical contacts to provide electrical isolation between the first and second electrical contacts.

FIELD

The present application generally relates to wearable biosensors, and more particularly relates to sensor interposers employing castellated through-vias.

BACKGROUND

Existing wearable biosensors, such as continuous glucose monitors, integrate an analyte sensor into the wearable device as a complete module assembly so that the device may be applied to the body and the sensor wire deployed into the body simultaneously with a single action. As a result, the sensor wire must be electrically connected and mechanically assembled to the device prior to deployment, during device manufacturing or assembly.

DETAILED DESCRIPTION

Examples are described herein in the context of sensor interposers employing castellated through-vias. 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.

Some wearable biosensors employ one or more invasive sensor wires that are inserted into a wearer's skin. The sensor wire typically includes at least two discrete electrodes and has a quantity of a chemical substance, such as glucose oxidase (“GOX”), deposited on the end of the sensor wire that is inserted into the wearer's skin. The chemical then reacts with an analyte present in the wearer's interstitial fluid, which generates a current that can be sensed by the biosensor's electronics. However, because the amount of current generated can be very small, e.g., on the order of tens of nanoamps, and because these chemical substances can be sensitive to heat, the design and manufacture of the biosensor can be difficult. For example, the biosensor must be designed to prevent leakage currents that might interfere with the current generated by the reaction between the chemical substance and the analyte. In addition, manufacturing processes that include high-heat steps, such as soldering, may damage the chemical substance if it is heated.

To address these and other challenges, an example wearable biosensor may employ a main PCB having electronics, such as a microcontroller or wireless transceiver, a battery, etc. In addition, the example device employs a secondary PCB assembly to mechanically secure the sensor wire (generally referred to as an “interposer”), while also providing electrical contacts to different electrodes present on the sensor wire. The interposer can then be electrically and physically coupled to the main PCB, such as by soldering. To help reduce the amount of heat transferred to the interposer during soldering, an example interposer employs castellated through-vias to provide electrical connections between the main PCB and interposer and to provide soldering locations relatively thermally isolated from the sensor wire itself.

In this example, the interposer has through-vias formed around the perimeter of the interposer's footprint. The interposer is then cut from a larger PCB sheet such that the through-vias are cut, exposing the interior portions of the through-vias. The exposed interior portions of the through-vias may be aligned with corresponding electrical contacts on the main PCB and soldered together. Because the solder points are located inside of the through-vias and essentially at the other side of the PCB from the electronics on the interposer PCB, heat transfer from the soldering process to the interposer electronics, including the sensor wire, is substantially reduced. In addition, using through-vias enables one or more guard rings to be formed to encircle the interposer and provide electrical isolation between different electrical contacts formed on the interposer, such as the electrical contacts to different electrodes formed within the sensor wire.

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 and examples of systems and methods for sensor interposers employing castellated through-vias formed in a PCBs.

Referring now toFIG. 1,FIG. 1shows an example sensor interposer100employing castellated through-vias. In this example, the sensor interposer includes a planar substrate, a PCB in this example. Any suitable PCB material may be employed, including FR4, polyimide, etc. Two electrical contacts112,114are formed on an upper surface of the PCB. Each electrical contact112,114is sized and shaped to enable a sensor wire120to be electrically and physically coupled to it, e.g., by clamps, adhesive, or any other suitable physical coupling technique. In this example, the sensor wire is formed from two electrodes formed coaxially, and, prior to use, a sensor chemical (e.g., glucose oxidase) may be deposited on a distal end of the sensor wire, i.e. the end of the sensor wire to be inserted into the wearer's skin. The proximate end of the sensor wire exposes each electrode to enable each electrode to be electrically and physically coupled to a different one of the electrical contacts112,114. In this example, the working electrode (“WE”) is coupled to electrical contact114, while the counter electrode (“CE”) is coupled to electrical contact112. In addition, each electrical contact112,114is electrically coupled to a castellated through-via formed on the perimeter edge of the PCB material. Once the interposer100is physically and electrically coupled to a main PCB, the castellated through-vias118will provide an electrical connection between the electrical contacts112,114and sensor electronics positioned on the main PCB. While in this example, the interposer100has two electrical contacts112,114, some examples may employ multiple sensor wires, which may require additional electrical contacts based on the type(s) of sensor wire(s) employed. Further, in some examples, the sensor wire may include more than two electrodes. For example, multiple electrodes may be formed on top of each other in successive planar layers. Each layer may be coupled to a different electrical contact formed on the planar substrate. Further, different electrodes may have different sensor chemicals applied to them. Suitable sensor chemicals include chemicals to sense acetyl choline, amylase, bilirubin, cholesterol, chorionic gonadotropin, creatine kinase (e.g., CK-MB), creatine, DNA, fructosamine, glucose, glutamine, growth hormones, hormones, ketones, lactate, peroxide, prostate-specific antigen, prothrombin, RNA, thyroid stimulating hormone, or troponin.

In this example, the planar substrate110(or interposer substrate) also defines an opening124between the two electrical contacts. The opening provides physical separation between the two electrical contacts112,114, thereby providing some electrical isolation between them. In addition, the opening enables the formation of guard traces116a-bthat do not intersect or contact the sensor wire120. In some examples, the opening may be formed having a shape corresponding to one or more features formed on the main PCB to enable alignment. It should be appreciated, however, that such an opening is not required in all examples, and may be omitted based on design considerations.

In addition to the electrical contacts112,114, two guard traces116a-bhave been formed on the interposer PCB. Each guard trace116a-bencircles a portion of the interposer PCB to provide electrical isolation between the two electrical contacts112,114. In this example, each guard ring includes a portion formed on the upper surface of the interposer PCB110that electrically couples two corresponding castellated through-vias. Each guard ring116a-balso includes a portion formed on the lower surface of the interposer PCB110that is also coupled to the same corresponding castellated through-vias to provide a closed loop of material encircling a portion of the interposer PCB. In combination with the opening, the two guard rings116a-belectrically isolate the two electrical contacts112,114from each other. In some examples, one or both of the guard rings116a-bmay be coupled to a ground plane to help dissipate leakage current.

In this example, the interposer100also includes a sensor wire120that is coupled to the two electrical contacts112,114. The sensor wire120in this example has two wire materials arranged coaxially, one of which operates as a working electrode and the other operates as a reference electrode or a counter electrode. To enable the two different coaxial portions of the sensor wire to couple to different electrical contacts, the interior wire material extends beyond the end of the exterior wire material, though a portion of it is covered by a polyurethane insulation122. In this example, the interior wire material is physically and electrically coupled to one electrical contact114and the exterior wire material is physically and electrically coupled to the other electrical contact112.

In this example, the sensor wire materials are (1) a platinum or platinum-coated wire, which is the interior wire material, and (2) a silver/silver-chloride (Ag/AgCl) material that is the exterior wire material. One end of the sensor wire120and a portion of the Ag/AgCl material are inserted into the patient's skin, while the other end of the sensor wire120is attached to the electrical contacts. The Ag/AgCl material is coupled to the first electrical contact112, while the platinum material is coupled to the second electrical contact114.

Referring now toFIG. 2,FIG. 2illustrates another example sensor interposer200employing castellated through-vias. In this example, the interposer200is formed from a planar substrate, which is a PCB210. Similar to the example shown inFIG. 1, the interposer200has two electrical contacts230a-bformed on it. A sensor wire250is physically and electrically coupled to the electrical contacts230a-b. In particular, the sensor wires has two coaxial electrodes252a-b, which are physically and electrically coupled to the respective electrical contacts230a-b. Each electrical contact230a-bis electrically coupled to a corresponding castellated through-via220b,220cby an electrical trace formed on the PCB210. The castellated through-vias may later be physically and electrically coupled to electrical contacts on another PCB to allow electrical signals from the sensor wire250to be communicated to the other PCB.

The interposer200also includes a guard trace240formed on the PCB210. The guard trace240traverses the PCB210between two castellated through-vias220a,220dand between the two electrical contacts230a-b, thereby electrically isolating them from each other. In this example, the guard trace240is formed both on the upper surface of the PCB (shown inFIG. 2) as well as on the lower surface, opposite the upper surface, where a further electrical trace is formed between the castellated through-vias220a,220d. However, in some examples, the guard trace240may only be formed on the same surface as the electrical contacts230a-b. In this example, unlike the example shown inFIG. 1, the PCB does not define a central opening. Thus, the guard trace240must run beneath the sensor wire250without contacting the sensor wire250, which may disrupt electrical signals provided by the sensor wire250to the electrical contacts230a-b.

Referring now toFIGS. 3A-3B,FIG. 4Ashows an example sensor interposer300employing castellated through-vias formed in a PCB. In this example, the interposer300has a PCB310planar substrate that defines a central opening322. In addition, the PCB310has four castellated through-vias formed on its perimeter, while two castellated through-vias are formed on the perimeter of the central opening322.

Two electrical contacts312,314are formed on the upper surface of the PCB and are each electrically coupled to a corresponding castellated through-via formed on the perimeter of the central opening322. The electrical contacts312,314are arranged to physically and electrical couple to a sensor wire220.

In addition to the electrical contacts312,314, two “wrap-around” guard traces316a-bare formed on the PCB310. Each guard trace316a-bencircles a portion of the PCB310to provide electrical isolation between the two electrical contacts312,314. In this example, each guard trace316a-bincludes a portion formed on the upper surface of the PCB310that electrically couples two corresponding castellated through-vias. Each guard trace316a-balso includes a portion formed on the lower surface of the PCB310that is also coupled to the same corresponding castellated through-vias to provide a closed loop of material encircling a portion of the PCB310. In combination with the opening, the two guard traces316a-belectrically isolate the two electrical contacts312,314from each other. In some examples, one or both of the guard traces316a-bmay be coupled to a ground plane to help dissipate leakage current.

FIG. 3Bshows a lower surface of the PCB310. The view shown inFIG. 4Balso illustrates the wrap-around guard traces316a-b, which are electrically coupled by a guard trace316cthat couples the two castellated through-vias formed in the perimeter of the opening. In some examples, guard trace316cis not included, thus the two wrap-around guard traces316a-bare electrically isolated from each other on the PCB310, though in some examples, they may be coupled to a common ground plane, such a common ground plane formed on a main PCB of a biosensor.

Referring now toFIG. 4,FIG. 4shows an example sensor interposer400employing castellated through-vias formed in a PCB. Such an example sensor interposer400may be integrated within a wearable biosensor, such as a continuous glucose monitor (“CGM”). An example CGM may include a main PCB that includes various electronic components, including a processor, discrete electronic components, and a wireless transceiver. A battery may be mounted on and electrically coupled to the CGM's main PCB to supply power to the electronic components of the CGM.

The example sensor interposer400may be physically and electrically coupled to the main PCB to enable signals from the CGM's sensor wire, physically and electrically coupled to the sensor interposer400, to be provided to electronic components on the main PCB, such as the processor.

The sensor interposer400in this example includes two electrical contacts412,414formed on one side of the interposer400, which are physically separated by an opening422defined in the perimeter of the interposer400. Each electrical contact412,414is electrically coupled to a castellated through-via. In addition, a guard trace416is formed on the same surface of the PCB410as the two electrical contacts412,414and provides electrical isolation between the two electrical contacts412,414.

In addition to the electrical contacts and guard trace416, the interposer400also includes additional electrical features. In this example, an electrical tracer designed as an antenna430is formed on the PCB410, and electrically coupled to a castellated through-via to enable electrical and physical coupling to the CGM's main PCB. In some examples, still other electrical features may be provided on the PCB, including additional electrical contacts to physically and electrically couple one or more additional sensor wires.

In some examples, the interposer400may be formed separately from the main PCB, and the sensor wire may be physically and electrically coupled to the interposer400before the interposer400is physically and electrically coupled to the CGM's main PCB; however, as will be discussed with respect toFIG. 6, other sequences may be employed as well.

Referring now toFIGS. 5A-5C,FIG. 5Ashows an example wearable biosensor device500that includes a sensor interposer520employing castellated through-vias. In this example, the wearable biosensor device500includes a main PCB510on which are positioned a sensor interposer520and a sensor controller540. This example device500includes the example sensor interposer shown inFIG. 3; however, any suitable sensor interposer employing castellated through-vias may be employed.

In this example, the main PCB510also defines a surface feature512, such as a pin that engages with an opening defined in the sensor interposer520.FIG. 5Billustrates the main PCB510, which has a surface feature512defined on it. The surface feature512provides an alignment feature to enable alignment of the sensor interposer520with the main PCB510and one or more electrical contacts formed on the main PCB510.FIG. 5Cillustrates a top-down view of the main PCB510, which has the surface feature512formed and positioned to engage with a sensor interposer520. In addition, the main PCB510has four electrical contacts514a-dformed to engage with the sensor interposer's castellated through-vias522a-d.

Referring now toFIG. 6,FIG. 6shows an example method600for manufacturing a sensor interposer employing castellated through-vias formed in a PCB. The example method600will be described with respect to the example sensor interposer100shown inFIG. 1; however, example methods according to this disclosure may be employed to manufacture any suitable example sensor interposer according to this disclosure.

At block610, a suitable planar substrate110is provided. In this example, the planar substrate110is a PCB formed of a suitable material, such as FR4 or polyimide. The planar substrate110in this example has a larger size than the designed sensor interposer100. Thus, at a later step, the planar substrate110may be cut to the designed size for the sensor interposer100.

At block620, one or more through-vias118are formed in the planar substrate110, such as in locations corresponding to a designed perimeter of a sensor interposer100. Such through-vias118may be formed having substantially circular (or other) cross-sections, where a portion of the through-via's perimeter extends outside of the designed perimeter of the sensor interposer100. In some examples, one or more through-vias118may be formed in an interior portion of the sensor interposer100as well. Such through-vias118may be formed around a designed perimeter of an opening to be defined in the sensor interposer100. For example, referring again toFIG. 1, two through-vias were formed in the PCB110and were cut to form castellated through-vias when the central opening in the PCB110was formed. Any suitable number of through-vias may be formed according to different examples. In this example, four through-vias are formed on the designed perimeter of the sensor interposer, while two additional through-vias are formed on the designed perimeter of a central opening of the sensor interposer100.

At block630, the planar substrate110is cut along a designed perimeter of the sensor interposer100, including cutting the through-vias to form castellated through-vias118. In this example, the planar substrate110is further cut to form the central opening124and the castellated through-vias in the perimeter of the central opening124.

At block640, two electrical contacts112,114are formed on the PCB110within the designed perimeter of the sensor interposer100. In this example, the electrical contacts112,114are formed to enable physical and electrical coupling of a sensor wire120and are formed on opposite sides of a designed central opening124. In this example, both electrical contacts112,114are formed on the same surface of the PCB110; however, in some examples, they may be formed on opposite sides of the PCB100. For example, if each electrode of a sensor wire is formed into a discrete wire, they may be coupled to opposite sides of the PCB110. And while in this example, two electrical contacts are formed, in some examples, more than two electrical contacts may be formed. For example, if multiple sensor wires are to be affixed to the sensor interposer, a pair of electrical contacts may be formed for each sensor wire or sensor electrode.

In addition to forming the electrical contacts at block640, an electrical trace from each electrical contact112,114is formed to electrically couple the respective electrical contact112,114to a corresponding castellated through-via. In some examples, the electrical traces may be serpentine to extend their length to reduce heat transfer from the castellated via to the electrical contact when the interposer is later soldered to the main PCB.

At block650, one or more guard traces116a-bare formed on the PCB110. In this example, electrical traces are formed to couple castellated through-vias to each other to electrically isolate the electrical contacts. For example, referring toFIG. 3A, electrical traces are formed between the castellated through-vias formed in the perimeter of the central opening322and a corresponding castellated through-via formed in the perimeter of the PCB310. Such traces are formed on both the upper and lower surfaces of the PCB310to create guard traces that encircles the PCB210. In addition, in this example, a guard trace316cis formed between the castellated though-vias formed in the perimeter of the central opening322to couple the two wrap-around guard traces316a-b; however guard trace316cis optional and may be omitted in some examples.

At block660, a sensor wire120is coupled to the electrical contacts112,114. As discussed above, a sensor wire120may be a coaxial sensor wire120having two different wire materials with the inner wire material extending beyond the outer wire material at one end of the sensor wire120. A portion of the exposed inner wire material may be physically and electrically coupled to one of the electrical contacts114, such as by soldering or using a clip or other electrical coupling means. A portion of the outer wire material may be coupled to the other electrical contact112using any suitable electrical coupling means.

At block670, suitable sensor chemistry, such as glucose oxidase, is deposited on the end of the sensor wire120distal from the sensor interposer100.

At block680, the sensor interposer100is coupled to a biosensor's main PCB. In this example, the sensor interposer100is soldered to the main PCB using each of the castellated through-vias formed in the perimeter of the sensor interposer. In some examples, the castellated through-vias formed in the perimeter of the central opening may be soldered instead or in addition.

While the steps of the method600above were described in a particular order, it should be appreciated that different orders may be employed according to different examples. For example block630maybe performed after block650, or block650may be performed before block640or block630.