High-isolation current sensor

Abstract

Methods and apparatus for providing a high-isolation current sensor. In embodiments, a current sensor includes a leadframe having a first portion and a second portion of a current conductor, a magnetic field sensing element positioned relative to the current conductor for detecting a magnetic field generated by current flowing through the current conductor, and a die supported by at least a portion of the first portion and / or the second portion of the leadframe, wherein the first portion of the leadframe includes an isolation region aligned with a first edge of the die. In embodiments, the current sensor includes features to enhance active layer isolation and SOI processing.

Description

Technical Field

[0001] This application relates to the field of current sensors, and more particularly to a high-isolation current sensor. Background Technology

[0002] As is known in the art, some current sensors use a magnetic field sensing element near a current-carrying conductor. This sensing element can generate an output signal whose amplitude is proportional to the magnetic field induced by the current flowing through the current-carrying conductor.

[0003] Several parameters characterize the performance of a current sensor, including sensitivity. Sensitivity is related to the magnitude of the change in the output voltage of the sensing element in response to a sensed change in current. The sensitivity of a current sensor is affected by a variety of factors, including the physical distance between the sensing element and the conductor.

[0004] Furthermore, current sensors typically have a limited operating range relative to the magnitude of the current they can sense and therefore measure. However, some applications may require sensing currents that are larger in magnitude than the operating range of the corresponding current sensor. The voltage level of the signal to be sensed may be limited by the isolation characteristics of the sensor. Summary of the Invention

[0005] Exemplary embodiments of the present invention provide methods and apparatus for high-isolation current sensors. In embodiments, the electrical isolation between the die and the current-carrying portion of the lead frame can be increased, for example, by etching an isolation region in the lead frame to increase the distance from the die to the current-carrying portion of the lead frame. In some embodiments, SOI processes and configurations are used to enhance the isolation of the current sensor.

[0006] In one aspect, the current sensor includes: a lead frame having a first portion and a second portion, wherein the first portion of the lead frame includes a current conductor; a magnetic field sensing element positioned relative to the current conductor for detecting a magnetic field generated by a current flowing through the current conductor; and a die supported by at least a portion of the first portion and / or the second portion of the lead frame, wherein the first portion of the lead frame includes an isolation region aligned with a first edge of the die.

[0007] The current sensor may further include one or more of the following features: an insulating layer applied to the lead frame-facing surface of the die; a first edge of the die extending into an isolation region at least partially filled with an insulating molding compound; a shortest distance from the edge of the die to a location on the first portion of the lead frame greater with the isolation region than without it; a current conductor having a U-shaped portion aligned with a magnetic field sensing element; the length of the isolation region being greater than the length of the first edge of the die; the die being configured in a flip-chip configuration; the die being configured in a die-up configuration; the die being configured in a chip-on-a-chip configuration; the die including a silicon-on-insulator (SOI) configuration; the die including a bulk silicon layer, an oxide layer, and an active layer; a non-conductive layer adjacent to the active layer; a trench formed in the active layer and at the edge of the die, wherein the trench is filled with an insulating material; and a second lead frame portion configured to be larger than the first lead frame portion. A higher voltage is provided, and the trench is located above the second portion of the lead frame. The active layer is divided into a first portion and a second portion and electrically isolated from each other by an isolation island. The first portion of the active layer is electrically connected to the first lead frame portion and the second portion of the active layer is electrically connected to the second lead frame portion. The second lead frame portion is configured for a higher voltage than the first lead frame portion. The sensor has a flip-chip configuration, and the die includes a bulk silicon layer, an oxide layer, and an active layer. The bulk silicon layer is disposed on the second portion of the lead frame with the die facing upward. The second lead frame portion is configured for a higher voltage than the first lead frame portion. The sensor has a flip-chip configuration, and the active layer is wire-bonded to the first lead frame portion. The active layer is surrounded by trenches filled with insulating material and / or a non-conductive material layer between the bulk silicon layer and the second lead frame portion.

[0008] On the other hand, the current sensor includes: a lead frame having a first portion and a second portion, wherein the first portion of the lead frame includes a current conductor, and the first portion and the second portion of the lead frame are separate from each other; a magnetic field sensing element positioned relative to the current conductor for detecting a magnetic field generated by a current flowing through the current conductor; and an SOI die supported by at least a portion of the first portion and / or the second portion of the lead frame, wherein the die includes a silicon layer, an oxide layer, and an active layer.

[0009] The current sensor may further include one or more of the following features: the die further includes an insulating adhesive layer on an active layer, the active layer including oxide portions at the edges of the active layer, a second portion of the lead frame configured for a lower voltage than a first portion of the lead frame, wherein the active layer is coupled to the second portion of the lead frame, the oxide portions at the edges of the active layer are aligned above the first portion of the lead frame, the adhesive layer includes BCB or polyimide, the die is supported by the first and second portions of the lead frame, wherein the active layer is separated into separate first and second portions by oxide islands, wherein the first portion of the active layer is connected to the first portion of the lead frame, and the second portion of the active layer is connected to the second portion of the active layer, the first portion of the active layer is connected to the first portion of the lead frame through a first through-hole and a first solder bump, and the second portion of the active layer is connected to the first portion of the lead frame through a second through-hole and a first solder bump. Through-holes and second solder bumps are connected to a second portion of the active layer. The current sensor has a die-up configuration, wherein a silicon layer of the die is disposed on a first portion of the lead frame, and wherein the active layer of the die is connected to a second portion of the lead frame via bonding wires. The active layer includes a first oxide portion and a second oxide portion at the edge of the die, a non-conductive layer between the silicon layer and the first portion of the lead frame, the non-conductive layer including a strip with an area larger than the area on the lead frame side of the die, the non-conductive layer including a die-attachment material, the first portion of the lead frame including an isolation region aligned with a first edge of the die, an insulating layer applied to the lead frame-facing surface of the die, the first edge of the die extending into the isolation region, the isolation region being at least partially filled with an insulating molding compound, and / or the shortest distance from the edge of the die to a location on the first portion of the lead frame is greater with the isolation region than without it. Attached Figure Description

[0010] The above features can be more fully understood from the following description of the accompanying drawings, wherein:

[0011] Figure 1 It is a partially transparent perspective view of a current sensor with enhanced isolation;

[0012] Figure 2 yes Figure 1 An exemplary pin assignment diagram for the sensor;

[0013] Figure 3 yes Figure 1 An exemplary functional block diagram of the sensor;

[0014] Figure 3A It has differential sensing capabilities. Figure 1 An exemplary functional block diagram of the sensor;

[0015] Figure 4A yes Figure 1A partially transparent perspective view of a portion of the sensor;

[0016] Figure 4B yes Figure 1 A partially transparent top view of a portion of the sensor;

[0017] Figure 4C yes Figure 1 A partially transparent perspective view of a portion of the sensor;

[0018] Figure 5A It is a partially transparent perspective view of a portion of a sensor with enhanced isolation located in a lead-chip configuration;

[0019] Figure 5B yes Figure 5A A partially transparent top view of a portion of the sensor;

[0020] Figure 6A It is a partially transparent perspective view of a portion of the sensor, which has enhanced isolation in a die-up configuration in the current loop;

[0021] Figure 6B yes Figure 6A A partially transparent top view of a portion of the sensor;

[0022] Figure 7A This is a schematic diagram of current sensing with enhanced isolation, in which the SOI substrate is in a flip-chip configuration;

[0023] Figure 7B This is a schematic diagram of current sensing with enhanced isolation, in which the SOI substrate is in a flip-chip configuration and connected to the high-voltage portion of the leadframe;

[0024] Figure 8A This is a schematic diagram of current sensing with enhanced isolation, wherein the SOI substrate is in a die-up configuration; and

[0025] Figure 8B This is a schematic diagram of another current sensing with enhanced isolation, in which the SOI substrate is in a die-up configuration. Detailed Implementation

[0026] Figure 1An exemplary current sensor 100 with a lead frame 102 is shown, which is etched to enhance the voltage isolation level. The lead frame 102 is etched to increase the electrical isolation between the die 104 and the lead frame 102b by increasing the separation distance, which may also be referred to as the creepage distance. It is understood that increasing the distance between different materials, especially conductive materials, increases electrical isolation. It is also understood that, in addition to the separation distance, the materials also have dielectric properties, which can determine the isolation voltage level and the creepage distance. For example, a mold compound with a high dielectric constant can be selected to achieve the desired higher electrical isolation.

[0027] In the illustrated embodiment, the current sensor 100 is shown as partially transparent and without a package to aid in understanding this disclosure. It is understood that the current sensor 100 may be provided as an integrated circuit (IC) package with leads. Figure 1 The current sensor 100 has a flip-chip configuration with a bare die with bumps and solder bumps, for example, thereby providing an electrical connection between the bare die and the lead finger.

[0028] The current sensor 100 has a die 104 supported by a lead frame 102, which has a first portion 102a and a second portion 102b. In an embodiment, the first portion 102a and the second portion 102b are formed as separate portions of a conductive material such as copper. The first portion 102a is connected to first pins, second pins, third pins, and fourth pins 106e-h, while the second portion 102b is connected to fifth pins, sixth pins, seventh pins, and eighth pins 106a-d. The pins can provide external I / O for the sensor IC package.

[0029] Die 104 may include analog and / or digital signal processing circuitry 110 to process signals from magnetic field sensing element 108, which senses a magnetic field generated by current flowing through a pin. It is understood that, in the illustrated embodiment, the circuitry for the digital signal processing circuitry 110 and the magnetic field sensing element 108 is located on the lead frame side of the die. In an exemplary embodiment, first pin 106a and second pin 106b are single nodes providing current input (or output), and third pin 106c and fourth pin 106d are single nodes providing current output (or input). This path can be considered a current conductor to which the current to be measured by the current sensor can be connected using external I / O of the sensor IC package. In the illustrated embodiment, the current conductor includes an arcuate portion 111 for focusing current flow to enhance magnetic field detection by the magnetic field sensing element 108. Any practical number and type of magnetic field sensing element can be used to meet the needs of a specific application. The etching of the lead frame 102 near die 104 is discussed in detail below.

[0030] Processing circuitry 110 may include calibration circuitry for calibrating the sensitivity of a sensor. For example, the magnetic field sensing element 108 may experience sensitivity variations due to, but not limited to, temperature changes in the environment surrounding and / or inside the current sensor 100. These sensitivity variations affect the performance of the magnetic field sensing element 108 and thus the accuracy of the output signal of the current sensor 100. The calibration circuitry may be configured to detect these sensitivity variations by comparing the expected output of the current sensor 100 with the measured output of the current sensor. The calibration circuitry may generate a compensation signal to modify and / or adjust the output signal, thereby causing the sensitivity variation.

[0031] Figure 2 An exemplary IC package 200 implementation and pin assignment diagram are shown. Current input (output) pins 1 and 2 can be supplied by... Figure 1 Pins 106a and 106b provide the input, and output (input) pins 3 and 4 can be provided by pins 106c and 106d. The output signal VIOUT on pin 7 outputs an analog signal that varies proportionally with the bidirectional AC or DC primary sense current IP within a specified measurement range. The FILTER pin can be used to reduce bandwidth to optimize noise performance.

[0032] Figure 3An exemplary current sensor implementation 300 for AC or DC current sensing is shown for applications such as motor control, load detection and management, switch-mode power supplies, and overcurrent fault protection. An applied current flowing through a current conductor generates a magnetic field, which is sensed by a magnetic field sensing element and converted into a proportional voltage. In this embodiment, the current is differentially sensed to suppress common-mode fields, thereby improving accuracy in magnetically noisy environments. Inherent device accuracy is optimized through close proximity of the magnetic field to the Hall transducer. A precise proportional voltage is provided by a low-offset, chopper-stabilized BiCMOS Hall IC, programmed to ensure accuracy after packaging. When an increased current flows through the primary copper conductive path (from pins 1 and 2 to pins 3 and 4), Figure 2 When the primary copper conductive path is used for current sensing, the device output has a positive slope. For example, the internal resistance of this conductive path is approximately 1.2 mΩ, providing low power loss. The terminals of the conductive path are electrically isolated from the sensor leads (pins 5 to 8), allowing the current sensor IC to be used in high-side current sensing applications without the need for a high-side differential amplifier.

[0033] like Figure 3 As shown, the current sensor 300 includes a magnetic field sensing circuit 350. A magnetic field sensing element 352, such as one or more Hall elements, is configured to sense the current. For example, the magnetic field sensing element 352 may be positioned such that it can sense the current when a magnetic field signal 352a is generated. The current can flow into the sensor 300 via current input / output pins 340a, 340b and 340c, 340d, which may be similar to... Figure 2 Pins 1, 2, 3, and 4 on the sensor IC 200.

[0034] The magnetic sensing element 352 may include a Hall effect element and / or a magnetoresistive element. For example, the magnetoresistive element may include at least one of indium antimonide (InSb), giant magnetoresistive (GMR) element, anisotropic magnetoresistive (AMR) element, tunnel magnetoresistive (TMR) element, or magnetic tunnel junction (MTJ) element.

[0035] A magnetic field signal 352a provided by the magnetic sensing element 352 is coupled to a first input terminal of a first amplifier 356. A second input terminal of the first amplifier 356 can be coupled to the output terminal of a sensitivity control circuit 354 configured to generate compensation for sensitivity variations experienced by the magnetic field sensing element 352. Therefore, in some embodiments, the sensitivity signal 354a may include compensation for sensitivity variations of the magnetic field sensing element 352. The first amplifier 356 can adjust the gain of the magnetic field signal 352a based on the value of the sensitivity signal 356a.

[0036] The output of the first amplifier 356 is coupled to the input of the filter 358. The filter 358 reduces the bandwidth of the current to be sensed and may include a low-pass filter. If the current being sensed is AC, the filter 358 may include a band-pass filter. The filter 358 may be configured to receive a signal 356a and generate a filtered signal 358a. The output of the filter 358 is coupled to the second amplifier 360. The output of the offset control circuit 362 may be coupled to the second amplifier 360 to provide an offset control signal 362a. The offset control signal 362a may include an offset value to reduce the offset of the filtered signal 358a (e.g., DC offset).

[0037] The second amplifier 360 may be configured to receive the filtered signal 358a and apply an offset control signal 362a to the filtered signal 358a to generate a second control signal 360a. In one embodiment, the output of the second amplifier 360 may be coupled to VI of the magnetic field sensing circuit 350. out Node. Therefore, the second control signal 360a can be the output of the magnetic field sensing circuit 350.

[0038] The magnetic field sensing circuit 350 may include a digital control circuit 370. The digital control circuit 370 includes a memory circuit 372 and a processor circuit 374. The memory circuit 372 may include volatile and non-volatile memory. The non-volatile memory may store computer instructions, an operating system, and / or data. The non-volatile memory may include one or more lookup tables for storing and organizing the captured data, as well as any tables or matrices generated using the captured data. In one example, the computer instructions may be executed by the processor circuit 374, which is located external to the volatile memory. In some embodiments, the sensitivity control circuit 354 and the offset control circuit 362 may be components of the digital control circuit 370.

[0039] In some embodiments, the magnetic field sensing circuit 350 includes a temperature sensor 376. The temperature sensor 376 may be configured to detect the temperature of the environment surrounding and / or inside the current sensor 300 and / or the magnetic field sensing circuit 350. In some embodiments, the temperature sensor 376 may detect temperature changes in the environment surrounding and / or inside the current sensor 300 and / or the magnetic field sensing circuit 350. For example, changes in the sensitivity of the magnetic field sensing element 352 may be caused by temperature changes. Therefore, the temperature sensor 376 may provide temperature information to the digital control circuit 370.

[0040] The output of temperature sensor 350 is coupled to the input of digital control circuit 370 to provide temperature signal 376a to digital control circuit 370. In some embodiments, temperature information from temperature signal 376a can be used to generate sensitivity signal 354a. For example, digital control circuit 370 can use temperature signal 376a to instruct sensitivity control circuit 354 to quantitatively compensate magnetic field signal 352a generated by magnetic field sensing element 352.

[0041] The magnetic field sensing circuit 350 may include a first reference voltage node 380, a second reference voltage node 366, and an output node 364. The first reference voltage node 380 (e.g., VCC) may be coupled to a voltage source. This voltage source may supply voltage to the magnetic field sensing circuit 350 and thus to each component of the magnetic field sensing circuit 350. The second reference voltage 366 may be coupled to ground. The output node 364 may correspond to the output terminal of the magnetic field sensing circuit 350.

[0042] Figure 3A An exemplary sensor 390 is shown, which is associated with Figure 3 The sensor 300 is similar to that of the exemplary sensor 390, which has a magnetic field sensing element 392 comprising a series of magnetoresistive sensing elements configured in a bridge positioned relative to a current conductor 394. The bridge configuration of the magnetic field sensing elements provides differential sensing.

[0043] Figure 4A -C illustrates further details of sensor 400, which has an etched lead frame 402 to enhance electrical isolation and creepage characteristics. Compared to a sensor without an isolation region, the bottom die edge extends into the isolation region to increase the distance from the die edge to the lead frame. By increasing this distance, the isolation voltage is increased, as described more fully below.

[0044] In this embodiment, the voltage potential associated with the signal side of the lead frame 402b on the current-carrying portion of the lead frame 402a can be from volts to kilovolts or higher. Increasing the isolation between the lead frame and the die is desirable for increasing the voltage level of the signal to be sensed. Suitable epoxy molding compounds are available from ROM SUMITOMO and include part numbers E670 and G700. These molding compounds have dielectric strengths from ~15 kV / mm to 20 kV / mm.

[0045] In an embodiment, the die 404 is supported by a lead frame 402 with various connectors 406 (e.g., solder) to various pins 407 that can provide I / O connections (e.g., IC package output signals with voltages proportional to sensed current levels), as described above.

[0046] The lead frame 402 has a top surface 408, which can form a plane supporting a portion of the die 404. As described above, the lead frame 402 may include an electrically isolated first lead frame portion 402a and a second lead frame portion 402b. The first lead frame portion 402a includes, for example, a U-shaped current conductor portion 412, above which a magnetic field sensing element in the die 404 may be positioned to sense a magnetic field generated by a current.

[0047] In an exemplary embodiment, the first lead frame portion 402a includes an isolation region 414 having a bottom surface 416 located below a top surface 408. The isolation region 414 may include a first side 418 located below a die 404 and a second side 420 located on the pin side of the first lead frame portion 402a. In an embodiment, the length of the isolation region 414 is longer than the length of the die 404. In an exemplary embodiment, the width of the isolation region 414 formed in the lead frame is twice the depth of the isolation region. It is understood that isolation is provided by the distance from the lead frame to the edge of the die. The depth of the isolation region 414 forms a distance X from the bottom of the etched portion to the edge of the die. If the width is twice this depth, then the distance from the edge of the etched portion to the edge of the chip is X.

[0048] In one embodiment, the die has an isolation layer on top of it that protects everything except the die edge from the main circuit. This isolation layer increases the distance from the main circuit to the die edge.

[0049] It is understood that isolation region 414 may include any practical geometry for increasing creepage distance and isolation voltage at the die edge and lead frame. For example, isolation region 414 may include circular channels, V-shaped, U-shaped, bulbous channels, etc., to meet the needs of a specific application.

[0050] like Figure 4B and Figure 4C Best viewed in the exemplary embodiment, the bottom edge 430 of the die 404 extends into the isolation region 414. The isolation region 414 increases the distance from the die edge 430 to the lead frame 402 compared to having no isolation region. By increasing this distance, the isolation voltage is increased. For example, the isolation voltage can be increased from approximately 3.5 kV without the isolation region 414 to approximately 4.3 kV with the isolation region.

[0051] To achieve leadframe-die isolation, an isolation layer (such as polyimide or BCB) is first placed on top of the circuitry, while sufficient isolation is provided throughout the die itself. These materials have dielectric strengths ranging from approximately 200 V / µm to 700 V / µm; therefore, depending on the material, 10 µm to 20 µm is sufficient to achieve an exemplary 4 kV isolation. The focus is on the path from the chip edge to the (current-carrying) high-voltage portion of the leadframe. If a 20 kV / mm molding compound is used, this is 20 V / µm. To achieve 4 kV, a distance of 200 µm through the molding compound is required. Depending on the die's sealing method, some isolation is also present at the die edge. Typically, a certain level, e.g., kV, is required through the molding compound, necessitating a certain distance (µm) through the compound. The bumps on the die may be approximately 20 µm to 50 µm high, requiring another 80 µm to 150 µm distance to achieve the desired isolation level. If we draw an arc from the edge of the die with a 180 μm long string, we can provide the required etching. In the embodiment, etching is used to form a square edge / shape. If we assume the bump height is 20 μm, then an etching depth of 160 μm is required, and it should be 360 ​​μm wide wherever it intersects with the edge of the die. In the embodiment, an etching depth of ~200 μm is performed because most etching is done as a "half" etching, and in the exemplary embodiment, this is a 400 μm thick leadframe.

[0052] Figure 5A and Figure 5B Top and perspective views of a high-isolation current sensor 500 with an on-chip lead configuration are shown, wherein a lead frame 502 supports an upward-facing die 504 such that the die I / O (and circuitry) are opposite the lead frame. Bond wires 505 are used to establish connections from the die 504 to the pins.

[0053] The lead frame 502 may be processed (e.g., etched) to form an isolation region 516, which increases the distance between the edge 530 of the die 504 and the lead frame 502 compared to not having an isolation region 516.

[0054] In one embodiment, the die 504 is coated with an insulating material 540 at least on the lead frame side of the die. This insulating material has relatively high dielectric properties to enhance the isolation between the die 504 and the lead frame 502.

[0055] Figure 6A and Figure 6BA current sensor 600 with a die-up configuration on a current loop is shown. Leadframes 602a and 602b have etched current loops 603 supporting a die 604. Leadframe 602 may include a pin 602a and a portion of the current loop 602b. An insulating layer 640 insulates the die 604 from the current loop 603. In the illustrated embodiment, the die 604 overlaps with a second portion 602b of the leadframe including the current loop 603, but not with a first portion 602a of the leadframe.

[0056] In one embodiment, the current loop 603 is etched to form an isolation region 616 that surrounds the adjacent die 604 of the current loop and the inner region 660 of the insulating layer 640. With this arrangement, the distance between the edges 630a, 630b, 630c, and 630d of the die and the material of the conductive current loop 603 is increased compared to the absence of an isolation region. Typically, etching increases the distance from the metal to the die edge wherever the die edge and the current-carrying lead frame overlap.

[0057] On the other hand, current sensors may include a silicon-on-insulator (SOI) configuration to enhance isolation between the die and the lead frame. One or more oxide layers and / or other materials may seal the active circuitry and improve the isolation voltage level.

[0058] Figure 7A An exemplary current sensor 700 with a flip-chip configuration is shown, wherein a lead frame 702 is bumped to a die 704. The current sensor 700 can be coupled with or without an isolation region. Figure 4A The current sensor 400 of type -C has some similarities. In the illustrated embodiment, the die 704 is connected to a first portion 702a of the lead frame, the voltage of which is lower than that of the second portion 702b of the lead frame.

[0059] For example, die 704 includes a bulk silicon layer 706, an oxide layer 708 that may include SiO2, an active layer 710, and an adhesive layer 712 that may include benzocyclobutene (BCB) or polyimide. An insulating SiO2 layer 708 and a BCB / PI layer 712, suitable for solder bumping processes, are sealed around the active circuitry 710, where die 704 overlaps with a high-voltage second portion 702b of a leadframe that provides a current-conducting loop. One or more solder balls 714 and vias 716 provide electrical connections from the active layer 710 to the second portion 702b of the leadframe.

[0060] In an embodiment, a first trench 720a is formed at the edge of the active layer 710 and filled with SiO2 or other insulating material. The SiO2-filled trench 720a (which may be about 0.4 mm) and the BCB layer 712 can be combined to enhance the electrical isolation between the die and the lead frame 702. In an exemplary embodiment, isolation exceeding 5 kV can be achieved.

[0061] Figure 7B An exemplary current sensor 700' with a flip-chip configuration is shown, which is... Figure 7A The current sensor 700 has commonalities and adds electrical connection to the high-voltage second lead frame portion 702b. In the illustrated embodiment, trenches 720 filled with an insulating material such as SiO2 electrically isolate the first portion 710a and the second portion 710b of the active layer.

[0062] SOI processing allows relatively deep trenches to isolate multiple portions of the active layer 710 of the die from each other. The SiO2-filled trenches 720 provide one or more isolation islands. In an exemplary embodiment, one or more solder bumps 724 provide connections to the high-voltage second portion 702b of the leadframe. Using this arrangement, the layout and package structure of a flip-chip current sensor with high isolation may be simpler than a cantilever approach. It is understood that... Figure 7A An exemplary cantilever configuration is shown. Isolation bumps can maintain consistent spacing by preventing bare sheet sagging.

[0063] Figure 8A An exemplary current sensor 800 with a die-up configuration is shown, having a bonding wire 801 from a low-voltage first portion 802a of a lead frame 802 to a die 804. The die 804 includes a bulk silicon layer 806, an oxide layer 808 that may include SiO2, and an active layer 810 to which the bonding wire 801 is attached. In the illustrated embodiment, the bulk silicon layer 806 of the die is supported by a high-voltage second portion 802b of the lead frame.

[0064] Insulation is provided by the SOI process and structure, and it can be the only insulation in a die-up structure. The SOI current sensor embodiment may offer higher isolation per micrometer than a non-conductive die-attached embodiment. Furthermore, trenches 820a and 820b can provide insulating trenches around the edges of the die 804. This forms a longer path through the molding compound to the active circuitry 810. In an exemplary embodiment, an isolation level of at least 5 kV can be achieved.

[0065] In an embodiment, the bonding wire 801 should rise from the die 804 (vertically) before descending to the low-voltage lead frame 802a, such that the distance from the high-voltage lead frame through the molding compound to the bonding wire is sufficient to meet the required isolation voltage level, for example, 5kV.

[0066] Figure 8B It shows having with Figure 8A An exemplary current sensor 800' with a similar die-up configuration as shown is provided, in which a non-conductive layer 825 is added, comprising a non-conductive die attachment and / or strip between the die 804 and the lead frame 802 to increase insulation. In an embodiment, the non-conductive layer 825, in the form of a die attachment material, only covers the lead frame 802 in the area where the die is located. In an embodiment, the non-conductive layer 825, in the form of a strip, is larger than the die 804. If the non-conductive layer 825 is sufficient to achieve isolation greater than a given threshold (e.g., 5 kV), then two isolation layers are effectively provided, and enhanced isolation can be obtained as long as the distance through the molding compound and / or adhesive joint is greater than, for example, about 0.4 mm.

[0067] What is understood is that Figures 7A to 8B The current sensor shown may or may not have an isolation region, for example Figure 1 and Figure 4A-6B The isolation zone shown in the image.

[0068] As used herein, the term "magnetic field sensing element" is used to describe a variety of electronic components capable of sensing magnetic fields. This magnetic field sensing element can be, but is not limited to, Hall effect elements, magnetoresistive elements, or magnetotransistors. Different types of Hall effect elements are known, such as planar Hall elements, vertical Hall elements, and circular vertical Hall (CVH) elements. Different types of magnetoresistive elements are also known, such as semiconductor magnetoresistive elements like indium antimonide (InSb), giant magnetoresistive (GMR) elements like spin valves, anisotropic magnetoresistive (AMR) elements, tunnel magnetoresistive (TMR) elements, and magnetic tunnel junctions (MTJs). A magnetic field sensing element can be a single element, or alternatively, it can include two or more magnetic field sensing elements arranged in various configurations, such as a half-bridge or a full (Wheatstone) bridge. Depending on device type requirements and other application requirements, the magnetic field sensing element can be a device made of type IV semiconductor materials such as silicon (Si) or germanium (Ge), or type III-V semiconductor materials such as gallium arsenide (GaAs), or indium compounds (e.g., indium antimonide (InSb)).

[0069] Some of the aforementioned magnetic field sensing elements tend to have a maximum sensitivity axis parallel to the substrate supporting the magnetic field sensing element, while others tend to have a maximum sensitivity axis perpendicular to the substrate supporting the magnetic field sensing element. In particular, planar Hall elements tend to have a sensitivity axis perpendicular to the substrate, while metal-based or metal magnetoresistive elements (e.g., GMR, TMR, AMR) and vertical Hall elements tend to have a sensitivity axis parallel to the substrate.

[0070] As used herein, the term "magnetic field sensor" is used to describe circuitry that uses a magnetic field sensing element, typically in combination with other circuitry. Magnetic field sensors are used in a variety of applications, including, but not limited to, angle sensors that sense the angle of a magnetic field direction, current sensors that sense the magnetic field generated by a current carried by a current-carrying conductor, magnetic switches that sense the proximity of a ferromagnetic object, rotation detectors that sense the passing of a ferromagnetic object (e.g., ferromagnetic targets such as gear teeth or magnetic domains of a toroidal magnet used in conjunction with a magnetic field sensor in combination with a reverse-biased or other magnet), and magnetic field sensors that sense the magnetic field density.

[0071] As used herein, the term "accuracy" in the context of a magnetic field sensor refers to several aspects of the sensor. These aspects include, but are not limited to, the sensor's ability to distinguish between gear teeth and gear valleys (or, more generally, the presence or absence of a ferromagnetic object) when the gear is not rotating and / or when the gear is rotating (or, more generally, when a ferromagnetic object is moving or not moving); its ability to distinguish between the edges of gear teeth and the teeth or valleys of the gear (or, more generally, the edges of a ferromagnetic object or changes in the magnetization direction of a hard ferromagnetic object); and the rotational accuracy in identifying the edges of gear teeth (or, more generally, the positioning accuracy in identifying the edges of a ferromagnetic or hard ferromagnetic object). Ultimately, accuracy refers to the accuracy of the output signal edge placement and its consistency with the edges of the gear teeth passing through the magnetic field sensor.

[0072] The terms “parallel” and “perpendicular” are used in various contexts throughout this document. It should be understood that the terms parallel and perpendicular do not require precise perpendicularity or parallelism, but are intended to apply nominal manufacturing tolerances, which depend on the context in which these terms are used. In some cases, the term “substantially” is used to modify the terms “parallel” or “perpendicular.” Typically, the use of the term “substantially” reflects angles beyond manufacturing tolerances, such as within + / - ten degrees.

[0073] Even when the air gap between the magnetic field sensor and the gear may change due to different installation methods or occasional variations, a certain level of accuracy or quantity of precision is desired for the magnetic field sensor. Even when there are variations in the relative positions of the magnet and the magnetic field sensing element within the magnetic field sensor, accuracy is desired for the magnetic field sensor. Even when there are inter-unit variations in the magnetic field generated by the magnet within the magnetic field sensor, accuracy is desired for the magnetic field sensor. Even when there are variations in the axial rotation of the magnetic field sensor relative to the gear, accuracy is desired for the magnetic field sensor. Even when there are temperature variations in the magnetic field sensor, accuracy is desired for the magnetic field sensor.

[0074] Preferred embodiments of various concepts, structures, and techniques used to illustrate the subject matter of this patent have been described; it is now apparent that other embodiments combining these concepts, structures, and techniques may be used. Therefore, the scope of this patent should not be limited to the described embodiments, but should be limited only by the spirit and scope of the appended claims.

Claims

1. A current sensor, comprising: A lead frame having a first lead frame portion and a second lead frame portion, wherein the first lead frame portion includes an arcuate current conductor portion extending from the edge of the first lead frame portion toward the second lead frame portion. A bare die supported by at least a portion of the first lead frame portion and / or the second lead frame portion; A magnetic field sensing element positioned relative to the current-conducting portion is used to detect the magnetic field generated by the current in the current-conducting portion; and An isolation region is etched into the first lead frame portion, wherein the isolation region has a bottom surface located below the top surface of the lead frame; The isolation region extends along a single direction aligned with the edge of the first lead frame portion, and the bottom edge of the die is configured to extend into and align with the isolation region to increase the distance from the bottom edge of the die to the first lead frame portion.

2. The current sensor according to claim 1, wherein, The current sensor also includes an insulating layer applied to the surface of the die facing the lead frame.

3. The current sensor according to claim 1, wherein, The isolation zone is at least partially filled with insulating molding compound.

4. The current sensor according to claim 1, wherein, The shortest distance from the edge of the die to a location on the first lead frame portion is greater with the isolation zone than without it.

5. The current sensor according to claim 1, wherein, The current conductor portion has a U-shaped portion aligned with the magnetic field sensing element.

6. The current sensor according to claim 1, wherein, The length of the isolation zone is greater than the length of the bottom edge of the bare die.

7. The current sensor according to claim 1, wherein, The die is configured as a flip-chip configuration.

8. The current sensor according to claim 1, wherein, The die is configured to be die-up.

9. The current sensor according to claim 1, wherein, The die is configured as a chip top lead configuration.

10. The current sensor according to claim 1, wherein, The die includes a silicon-on-insulator (SOI) configuration.

11. The current sensor according to claim 10, wherein, The die comprises a bulk silicon layer, an oxide layer, and an active layer.

12. The current sensor according to claim 11, wherein, The current sensor also includes a non-conductive layer adjacent to the active layer.

13. The current sensor according to claim 12, wherein, The current sensor also includes a groove formed in the active layer and at the edge of the die, the groove being filled with an insulating material.

14. The current sensor according to claim 13, wherein, The second lead frame portion is configured for a higher voltage than the first lead frame portion, and the trench is located above the second lead frame portion.

15. The current sensor according to claim 12, wherein, The active layer is divided into a first portion and a second portion and electrically isolated from each other by an isolation island. The first portion of the active layer is electrically connected to the first lead frame portion, and the second portion of the active layer is electrically connected to the second lead frame portion. The second lead frame portion is configured for a higher voltage than the first lead frame portion, and the sensor has a flip-chip configuration.

16. The current sensor according to claim 11, wherein, The bulk silicon layer is disposed on the second lead frame portion with the die facing upward.

17. The sensor according to claim 16, wherein, The second lead frame portion is configured for a higher voltage than the first lead frame portion, and the sensor has a flip-chip configuration, and the active layer is wire-bonded to the first lead frame portion.

18. The current sensor according to claim 17, wherein, The active layer is surrounded by trenches filled with insulating material.

19. The current sensor according to claim 18, wherein, The current sensor also includes a non-conductive material layer between the bulk silicon layer and the second lead frame portion.

Images