The present disclosure is generally directed toward optoelectronic devices and, in particular, opto-coupling devices.
In electronics, an opto-coupler, also referred to as an opto-isolator, photocoupler, or optical isolator, is an optoelectronic device designed to transfer electrical signals by utilizing light waves to provide coupling with electrical isolation between its input and output. One goal of an opto-coupler is to prevent high voltages or rapidly changing voltages on one side of the circuit from damaging components or distorting transmissions on the other side.
Generally, an opto-coupler comprises a light source (e.g., an optical transmitter die) and a light detector (e.g., an optical receiver die). The optical transmitter die and the optical receiver die may be housed in a single package. A multichannel opto-coupler may have more than one pair of optical transmitter or receiver dies. A signal is usually transmitted from the optical transmitter die to the optical receiver die. In order to prevent light loss, a light guide may be employed. In most cases, the light guide is formed by dispensing a transparent encapsulant in liquid form over the optical transmitter and receiver dies. The transparent encapsulant is then hardened through a curing process, thereby forming a light guide. Because the encapsulant is deposited in liquid form, the shape of the light guide may be difficult to control. This issue of controlling the light guide shape may be more severe for an opto-coupler with large dies or for a multichannel opto-coupler.
The present disclosure is described in conjunction with the appended figures, which are not necessarily drawn to scale:
The ensuing description provides embodiments only, and is not intended to limit the scope, applicability, or configuration of the claims. Rather, the ensuing description will provide those skilled in the art with an enabling description for implementing the described embodiments. It being understood that various changes may be made in the function and arrangement of elements without departing from the spirit and scope of the appended claims.
It is, therefore, one aspect of the present disclosure to provide an improved opto-coupler design that overcomes and addresses the above-mentioned issues. While examples discussed herein will be generally directed toward opto-couplers, it should be appreciated that the embodiments of the present disclosure are not so limited. For instance, the concepts described herein can be utilized in any type of isolator or isolation system (e.g., galvanic isolators), proximity sensors, optical encoders, or any other type of optical or non-optical device.
In some embodiments of the present disclosure an opto-coupler is provided with a light guide situated between the light source and the light detector. In some embodiments, the opto-coupler is provided with a light source, a light detector, and an encapsulant forming a light guide between the light source and the light detector, the encapsulant being at least partially supported by insulation or an insulative tape. In some embodiments, the light guide and the insulative tape on which the light guide is supported do not conduct electricity in much the same way to traditional insulation materials. An advantage to utilizing the insulative tape to at least partially support the encapsulant material is that the encapsulant can be deposited in a liquid or semi-liquid state and the insulative tape helps to maintain a desired form of the light guide even while the encapsulant is in a liquid or semi-liquid state.
In some embodiments, the encapsulant comprises an inherent surface tension and the shape of the encapsulant is at least partially dictated by the shape of the insulative tape. Specifically, the encapsulant, when deposited, may flow to the boundaries of the insulative tape and then begin forming a dome shape whose outer boundaries match or partially match the outer boundaries of the insulative tape. In this way, the insulative tape can be used to control how far the encapsulant flows during deposition and can maintain the shape of the encapsulant until the encapsulant is cured or hardened. In particular, the surface tension of the encapsulant causes the encapsulant to stop or slow flowing beyond the boundaries of the insulative tape.
In some embodiments, the encapsulant may correspond to a silicone or Ultraviolet-curable medium that is transparent or semi-transparent to light. The insulative tape may correspond to a polyimide film, a plastic tape, or a similar insulative material that can be formed into any desired shape. In particular non-limiting embodiments, the insulative tape may comprise one or more of Mylar, Polyimide, Kapton, Melinex, a dielectric tape, or any other similar material that is attachable to a leadframe, conductive element, or the like.
In some embodiments, the insulative tape provides the additional benefit of impeding a high-voltage failure path between a lead supporting the light source and a lead supporting the light detector. In particular, the insulative tape provides further insulative properties between conductive leads that are designed to be isolated from one another. Thus, the insulative tape can provide multiple benefits without substantially increasing manufacturing complexity or costs.
In some embodiments, a multi-channel opto-coupler is provided where one, two, three, four or more channels in the opto-coupler have a light guide situated between a light source and light detector of each channel. Each channel of the opto-coupler may have its own dedicated encapsulant or a single encapsulant may be provided around two or more sets of light sources and light detectors.
Additional details related to opto-couplers, including multi-channel opto-couplers, and their design are described in U.S. Patent Publication No. 2011/0235975 and U.S. Patent Publication No. 2012/0076455, each of which are hereby incorporated herein by reference in their entirety.
With reference now to
As can be seen in
Referring initially to
In some embodiments, the encapsulant 136 operates as a light guide or light-transmission medium to facilitate the passage of light from the light source 124 to the light detector 128. As is known in the opto-coupler arts, the light source 124 may activate or respond to electrical current or voltage present on a lead 112 of the first leadframe section 108a. Upon being activated, the light source 124 may release photons, which travel through the encapsulant 136 where they can be detected at the light detector 128. The light detector 128 then converts the light energy received at the light detector 128 back into an electrical signal that can be carried by another lead 112 of the second leadframe section 108b.
As shown in
The input side of the opto-coupler 100 may correspond to the first leadframe section 108a and one, some, or all leads 112 of the first leadframe section 108a may be configured for attachment to a circuit whose current and/or voltage is being measured. Conversely, the output side of the opto-coupler may correspond to the second leadframe section 108b and one, some, or all leads 112 of the second leadframe section 108b may be configured for attachment to circuitry operating at lower voltages and/or currents. As an example, the second leadframe section 108b may be connected to sensitive measurement and/or control circuitry. The gap between the first leadframe section 108a and second leadframe section 108b is generally provided to electrically insulate the currents/voltages at the input circuit from the output circuit.
The first leadframe section 108a and second leadframe section 108b may each comprise one or more electrically conductive leads 112. Moreover, although the shape of the leads 112 is shown to be configured for surface mounting (e.g., Surface Mount Technology (SMT)), it should be appreciated that the leads 112 may be straight or otherwise configured for thru-hole mounting to a Printed Circuit Board (PCB). In some embodiments, the leadframe may be initially provided as a sheet of conductive material having portions removed therefrom to establish discrete conductive elements or features (e.g., leads 112, bonding pads 116, etc.). The conductive elements of the leadframe including the leads 112 of both leadframe sections 108a, 108b may be constructed of metal (e.g., copper, silver, gold, aluminum, steel, lead, etc.), graphite, and/or conductive polymers.
The leads 112 of each leadframe section 108a, 108b may comprise a first end and second end and one or more of the leads 112 may further include an expanded area corresponding to the bonding pad 116. In some embodiments, the first end of each lead 112 may be contained within the housing 104 whereas the second end of each lead 112 may be exposed outside the housing 104. Thus, the first end of a lead 112 may be connected to internal circuitry or components of the opto-coupler 100 whereas the second end of a lead 112 may be connected to external circuitry, such as a PCB. Each lead 112 may also have one or more bends between their first end and second end, thereby establishing the shape of each lead 112 in the finished opto-coupler 100. In some embodiments, the bends and the length of the leads 112 extending beyond the housing 104 may be adjusted to suit the particular type of device to which the opto-coupler 100 will be connected. In other words, although embodiments of the present disclosure show the leads as having a specific configuration (e.g., SMT configurations), it should be appreciated that the leads or relevant sections protruding from the housing 104 may comprise any type of known, standardized, or yet-to-be developed configuration such as straight-cut leads, J leads, SOJ leads, gullwing, reverse gullwing, etc.
The housing 104 may be constructed of any material that is sufficient to protect internal components of the opto-coupler 100 and/or substantially prevent external light from reaching the optical pathway between the light source 124 and light detector 128, thereby introducing noise to the device. The housing 104, in some embodiments, may comprise non-conductive or insulative properties. Suitable types of materials that may be used as the housing 104 include, without limitation, plastic, ceramic, any substantially opaque or black compound, a white epoxy, any polymer or combination of polymers, any malleable or formable opaque material, or combinations thereof. The housing 104 may be manufactured using extrusion, machining, micro-machining, molding, injection molding, or a combination of such manufacturing techniques.
In some embodiments, the optical components of the opto-coupler 100 may be mounted directly on the leads 112, which extend out of housing 104. As an example, the light source 124 may be mounted on a bonding pad 116 of one lead 112 in the first leadframe section 108a and the light detector 128 may be mounted on a bonding pad 116 of a lead in the second leadframe section 108b. The mounting of optical components to a bonding pad 116 may be achieved by utilizing one or more of welding, adhesives, glue, mechanical structures (e.g., friction fits), etc.
In some embodiments, the encapsulant 136 corresponds to a transparent encapsulant and may be constructed of one or more of epoxy, silicone, a hybrid of silicone and epoxy, phosphor, a hybrid of phosphor and silicone, an amorphous polyamide resin or fluorocarbon, glass, plastic, or combinations thereof. In some embodiments, the encapsulant 136 may be deposited over the light source 124 and light detector 128 as well as wire bonds 132 connecting the optical components 124, 128 to the leads 112. Even more specifically, the encapsulant 136 may be deposited over the optical components 124, 128 and wire bonds 132 in a liquid or semi-liquid state and, thereafter, may be cured or hardened. As can be appreciated, the advantage to depositing an encapsulant 136 in a liquid or semi-liquid state is that it can be easily applied by a number of deposition processes. However, the downside to depositing an encapsulant 136 in a liquid or semi-liquid state is that it is difficult to control the shape of the encapsulant 136 until it is cured or hardened.
Previous solutions have attempted to control the shape of the encapsulant 136 with the use of forming elements (e.g., miniature molds or retaining structures). The present disclosure, on the other hand, suggests utilizing the insulative tape 120 as a mechanism for controlling the shape of the encapsulant 136 during deposition and after deposition until the encapsulant 136 is cured or hardened. As will be discussed herein, the insulative tape 120 may be utilized as the sole mechanism for controlling the shape of the encapsulant 136 prior to its curing or hardening.
Achieving a controllable and repeatable shape of the encapsulant 136 provides many advantages. First of all, if the shape of the encapsulant 136 can be maintained substantially constant from one opto-coupler 100 to another and from one manufacturing batch to another, the light transmission behavior of opto-couplers 100 can be more carefully controlled, thereby providing better and more consistent opto-couplers 100. Additionally, if the encapsulant 136 were to deform and not completely cover the optical components 124, 128 and/or wire bonds 132, then other failures may occur, thereby decreasing yield and profits. Further still, if the encapsulant 136 does not have a desired shape (e.g., smooth upper surface and flat lower surface), then the light path between the light source 124 and light detector 128 may be disrupted or non-optimal and the light emitted by the light source 124 may not completely arrive at the light detector 128. Thus, it is important to provide a mechanism for controlling the shape of the encapsulant 136, but it is also desirable to avoid any additional or complicated manufacturing steps.
In some embodiments, the light source 124 corresponds to a surface mount LED, a traditional LED (e.g., with pins for thru-hole mounting), an array of LEDs, a laser diode, or combinations thereof. The light source 124 is configured to convert electrical signals (e.g., current and/or voltage) from one or more leads 112 of the first leadframe section 108a into light. The light emitted by the light source 124 may be of any wavelength (e.g., either in or out of the visible light spectrum).
In some embodiments, the light detector 128 corresponds to device or collection of devices configured to convert light or other electromagnetic energy into an electrical signal (e.g., current and/or voltage). Examples of a suitable light detector 128 include, without limitation, a photodiode, a photoresistor, a photovoltaic cell, a phototransistor, an Integrated Circuit (IC) chip comprising one or more photodetector components, or combinations thereof. Similar to the light source 124, the light detector 128 may be configured for surface mounting, thru-hole mounting, or the like.
In some embodiments, one surface of the light source 124 is an anode and another surface of the light source 124 is a cathode. One of the anode and cathode may be electrically connected to the bonding pad 116 and the other of the anode and cathode may be electrically connected to a different lead 112 via a wire bond 132. By creating a potential between the anode and cathode of the light source 124, the light source 124 may be configured to emit light of a predetermined wavelength. It should be appreciated that not every lead 112 on the first leadframe section 108a needs to be connected either physically or electrically with the light source 124.
Like the light source 124, the light detector 128 may be mounted on a boding pad 116 of the second leadframe section 108b and may be electrically connected to another lead 112 via a wire bond 132.
With reference now to
The insulative tape 220 of
As shown in
However, once the encapsulant 236 reaches the outer boundary of the insulative tape 220 the inherent surface tension of the encapsulant 236 may maintain the encapsulant 236 in a desired shape at the outer boundary of the insulative tape 220 and oppose further spreading of the encapsulant. Accordingly, the force of gravity and the inherent surface tension of the encapsulant 236 can be equalized with an appropriately sized insulative tape 220, thereby enabling the insulative tape 220 to control the size and shape of the encapsulant 236 in a liquid or semi-liquid state until such time that the encapsulant 236 is cured or hardened.
Of course, the amount of encapsulant 236 deposited will impact whether or not the encapsulant 236 stops flowing at the outer boundary of the insulative tape 220. Furthermore, the viscosity of the encapsulant 236 and/or the dimensions of the insulative tape 220 will dictate whether the encapsulant 236 stops flowing at the boundaries of the insulative tape 220. It is contemplated that any amount of encapsulant 236 or dimension of insulative tape 220 may be accommodated without departing from the scope of the present disclosure.
In some embodiments, the insulative tape 220 can be the sole light guide-shaping element, thereby obviating the need for additional shaping mechanisms or molds. In the depicted embodiment, the elliptical insulative tape 220 can be used to create a dome-shaped encapsulant 236 with a particular thickness. In some embodiments, the thickness or height of the dome-shaped encapsulant 236 (e.g., distance between the top surface of the insulative tape 220 and top of the encapsulant 236) may be less than or equal to the conjugate diameter of the insulative tape 220. In embodiments where the wire bonds 232 extend to a lead 212 other than the one where the optical component 224, 228 is mounted, the insulative tape 220 may be extended or expanded to ensure that the encapsulant 236 covers some or all of the wire bond 232 that extends to another lead 212. Thus, although the embodiment of
In some embodiments, the insulative tape 220 may correspond to a polyimide film, a plastic tape, and/or a similar insulative material that is substantially flat and capable of being formed into any desired shape. Accordingly, the bottom surface of the encapsulant 236 may be substantially flat and smooth where it interfaces with the insulative tape 220 and the top surface of the encapsulant 236 may be substantially curved and smooth since the only force that shaped the top surface of the encapsulant 236 was gravity. Furthermore, since the encapsulant 236 obtained was self-formed with the assistance of gravity, the encapsulant 236 can remain in its desired shape until it is cured or hardened without any additional retaining members or molds.
With reference now to
The additional insulative tape 340 may be constructed of a material similar or identical to the material used for the insulative tape 320. The position of the additional insulative tape 340, however, helps to increase the distance between the bonding pads 316. While the additional insulative tape 340 is shown as being provided on the top surface of the leadframe sections 308a, 308b, it should be appreciated that the bonding pads 316 of the leadframe sections 308a, 308b may be cut or punched to have a shape that corresponds or mimics the shape of the additional insulative tape 340. Accordingly, it may also be possible to position the additional insulative tape 340 directly on top of the insulative tape 320 and on the same plane as the bonding pads 316. Alternatively or additionally, it may be possible to utilize the additional insulative tape 340 without the insulative tape 320.
In the depicted embodiment, the additional insulative tape 340 comprises an elliptical or oval shape, although it should be appreciated that a circular or non-elliptical shape could also be employed. The additional insulative tape 340 may help to minimize high-voltage failures of the opto-coupler by increasing the distance between the input and output side of the opto-coupler. In other words, the insulative tape 320 and additional insulative tape 340 can be used to help shape the encapsulant 336, improve coverage of the encapsulant 336 as well as reduce metal exposure, which could ultimately result in high-voltage failure. In some embodiments, the insulative tape 320 may provide the function of controlling the shape of the encapsulant 336 whereas the additional insulative tape 340 may provide the function of reducing the potential for high-voltage failure.
Referring now to
As seen in
With reference now to
With reference now to
The first and second insulative portions 620a, 620b may partially or completely cover the side surface of each bonding pad 616 that faces the other bonding pad. In this way, the insulative portions 620a, 620b create a longer metal-to-metal distance between the bonding pads 616, thereby mitigating possible high-voltage failures. It should be appreciated that a single insulative portion 620a or 620b may be used instead of relying upon a set of insulative portions. Moreover, the insulative portions 620a and/or 620b may wrap over the top and/or bottom surfaces of the boding pads 616 in addition to wrapping over the side surface of the bonding pads 616. It should also be appreciated that the material used for the insulative portions 620a, 620b may be similar or identical to the material discussed in connection with other insulative tapes disclosed herein.
Although not depicted, the opto-coupler component 600 may also comprise an encapsulant that covers the optical components 624, 628, the wire bonds 632, and the insulative portions 620a, 620b. In this embodiment, however, the insulative portions 620a, 620b are designed to mitigate arcing between the leadframe portions 608a, 608b instead of control the shape of the encapsulant in a liquid or semi-liquid state.
With reference now to
The method begins when a leadframe is received (step 704). The received leadframe may comprise multiple leads, some designed for an input side and some designated for an output side. In some embodiments, the leadframe may be received in a sheet-like format with features cut therefrom to at least partially establish the lead(s) and mounting section(s) of the leadframe. As can be appreciated, the leads of the leadframe may need to be bent of formed to accommodate the specific type of opto-coupler desired. This bending or folding may be performed at any point during the manufacturing process, but it should be noted that the leadframe may be received with or without the bends to the leads.
After the leadframe is received, the method continues by determining a desired encapsulant dome shape and size (step 708). The desired dome shape and size may be selected to accommodate a particular use-case for the opto-coupler. In some embodiments, the dome shape may be desired to have an elliptical cross section whereas other embodiment may require the dome shape to have a circular cross section.
The insulative tape is then formed according to the desired dome shape and size (step 712). In particular, the insulative tape may correspond to the lone mechanism that is used to form the encapsulant or maintain the encapsulant in a desired shape until it is cured or hardened. Any shape of insulative tape or insulative portion described herein may be utilized without departing from the scope of the present disclosure. The insulative tape or insulative tapes (e.g., additional insulative tape) are then positioned in proximity to the leadframe at the desired locations (step 716). This step may also include the process of attaching or adhering the insulative tape to the top, bottom, and/or side surfaces of the leadframes. Specifically, the insulative tape may be attached with an adhesive underneath the bonding pads, on top of the bonding pads, and/or on the side surfaces of the bonding pads.
Before, after, or simultaneous with any of steps 708, 712, and 716, the optical components may also be attached to the bonding pads of the opto-coupler (step 720). In some embodiments, these optical components may be attached to the leadframe using adhesives or the like, although such a configuration is not mandatory. The light source(s) and light detector(s) may then be electrically connected to the leadframe (step 724), if this was not already inherently done by virtue of mounting the components to the leadframe. Specifically, this step may involve connecting the light source(s) and/or light detector(s) to leads of the leadframe with one or more wire bonds.
Once the optical components are positioned and electrically connected as necessary, the method may proceed with the deposition of the encapsulant about the optical component(s), their wire bonds, and the bonding pads (step 728). In some embodiments, the encapsulant is deposited in a liquid or semi-liquid state. The types of processes that may be used to deposit the encapsulant include any type of known deposition technique such as those described in U.S. Patent Publication No. 2013/0102096, the entire contents of which are hereby incorporated herein by reference.
In some embodiments, the encapsulant flows to one, some, or all of the outermost boundaries of the insulative tape under the force of gravity. This flowing occurs until the liquid or semi-liquid encapsulant maintains an equilibrium between its inherent surface tension and the gravitational forces. The encapsulant may then be cured or hardened (step 732). The curing step may vary depending upon the type of encapsulant used. Examples of suitable curing or hardening steps include chemical curing, thermal curing, UV curing, air curing, or the like.
Once cured, the encapsulant may optionally be encapsulated or covered with a second encapsulant, such as housing 104 (step 736). In particular, a mold material or compound may be applied to the optical components and portions of the leadframe as well as the now-cured encapsulant protecting the optical components, thereby encapsulating the optical components within the mold material.
The method continues with one or more trimming and/or forming steps (step 740). In these trimming steps, the leads of the leadframe may be further defined and/or separated from one another. Furthermore, the trimming may involve removing leadframe material so as to appropriate size the leads of the lead frame to interface with a PCB, for instance. The forming steps (e.g., bending steps) may be performed to achieve a completed opto-coupler. Specifically, the finally formed or trimmed leads may be bent such that the opto-coupler is easily inserted into or mounted on a PCB or the like.
Specific details were given in the description to provide a thorough understanding of the embodiments. However, it will be understood by one of ordinary skill in the art that the embodiments may be practiced without these specific details. In other instances, well-known circuits, processes, algorithms, structures, and techniques may be shown without unnecessary detail in order to avoid obscuring the embodiments.
While illustrative embodiments of the disclosure have been described in detail herein, it is to be understood that the inventive concepts may be otherwise variously embodied and employed, and that the appended claims are intended to be construed to include such variations, except as limited by the prior art.
This is a continuation-in-part of U.S. application Ser. No. 13/314,023, filed on Dec. 7, 2011, which is a continuation-in-part of U.S. application Ser. No. 12/945,474, filed on Nov. 12, 2010, which is a continuation-in-part of U.S. application Ser. No. 12/729,943, filed on Mar. 23, 2010, each of which are incorporated by reference herein in their entirety.
Number | Date | Country | |
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Parent | 13314023 | Dec 2011 | US |
Child | 13959464 | US | |
Parent | 12945474 | Nov 2010 | US |
Child | 13314023 | US | |
Parent | 12729943 | Mar 2010 | US |
Child | 12945474 | US |