Lead frame for sensor

Abstract

A lead frame for a current sensor is provided. The frame includes a conductive member having an average thickness, and a sensing region for generating a signal detectable by the current sensing element when a current flows through the lead frame. It also includes a routing zone outside of the sensing zone, the routing zone for routing the current toward the sensing zone. The routing region includes a region having a maximum area, the region having a predetermined average thickness. At least the sensing region includes an additional material disposed on the conductive member such that a total thickness of the sensing region is thicker than an average thickness of the maximum region.

Description

Technical Field

[0001] The present invention relates to the field of current sensing. More particularly, the present invention relates to the measurement of current using an integrated current sensor, and to an integrated current sensor and its manufacture. Background Art

[0002] Integrated current sensors are used in many applications where current needs to be monitored. These sensors redirect the current from its wire or track towards a sensing element, which picks up the signal. Since the sensing element is encapsulated within the integrated current sensor, this means that the current to be sensed is applied to a lead (commonly referred to as a "main lead") that carries the current to be sensed through the integrated current sensor. As such, the integrated current sensor needs to be able to withstand the current to be sensed as well as common forms of noise in the current.

[0003] Conventional current sensors are capable of functioning at currents up to 50A and can accept peak currents of several thousand amperes (typically up to 20kA). However, new products that handle high power are becoming more and more accessible to the public. Some recent applications of current sensors include electric vehicle applications, and energy harvesting devices such as solar panels. The currents handled in these systems reach values ​​above 50A, and peak currents reach above 20kA for several microseconds, or even tens of microseconds. Current sensors need to be reliable even with such currents. This may cause overheating, thermal damage, and even fusing of the conductors used for current redirection in existing current sensors.

[0004] It would be desirable to provide reliable current sensing that is capable of handling high currents while being integrated on other devices. Summary of the invention

[0005] An object of embodiments of the present invention is to provide a lead frame for an integrated current sensor, which lead frame is capable of carrying high currents and withstanding current surges without breaking or fusing. An object is to provide a sensor comprising such a lead frame for reliable and robust current measurement.

[0006] In a first aspect, the present invention provides a lead frame for a current sensor. The lead frame includes a conductive member having an average thickness, and a sensing region for generating a signal detectable by a current sensing element when current flows through the lead frame. It also includes a routing region outside the sensing region for routing current toward the sensing region. The routing region includes a region having a maximum area, the region having a predetermined average thickness. At least the sensing region includes additional material disposed on the conductive member, so that the total thickness of the sensing region is thicker than the average thickness of the maximum area.

[0007] An advantage of embodiments of the present invention is that standard lead frames can be used or reused in current sensors for new high intensity applications. An advantage is that high current densities can be provided with heat generation lower than that required to fuse the lead frame.

[0008] In some embodiments, the lead frame includes a necking over the sensing region.

[0009] An advantage of an embodiment is that current density may be increased locally for enhancing the magnetic signal while keeping heat dissipation low enough to avoid fusing or melting of components.

[0010] In some embodiments, the average thickness of the largest area of ​​the routing region is 250 microns.

[0011] An advantage of an embodiment is that a small amount of material is required. A further advantage is that industry standard thicknesses can be used for the lead frame components.

[0012] In some embodiments, the thickness of the sensing region is between 5% and 120% thicker than the average thickness of the conductive member (eg, between 10% and 80% thicker than the average thickness).

[0013] For example, the sensing region may be between 15 microns and 300 microns thicker than the average thickness.An advantage of an embodiment is that a local increase in thickness may be provided locally without significantly changing the form factor, so the LF may fit in a standard sensor package.

[0014] In some embodiments, the additional material disposed on the sensing region also extends beyond the sensing region into the routing region. Nevertheless, the area with added material is still smaller than the largest area of ​​the routing region with the average thickness of the conductive member.

[0015] An advantage of an embodiment is that the thicker region extending beyond the sensing area improves die stability.

[0016] In some embodiments, the piece is a sheet comprising two opposing planar faces, wherein the increase in thickness is provided on one or both faces of the sheet.

[0017] An advantage of an embodiment is that the thickness can be accurately controlled by providing additional material on both sides of the sheet.

[0018] In some embodiments, the additional material on one side of the sheet covers a first area and the additional material on the opposite side covers a second area, wherein the first area is larger than the second area.

[0019] An advantage of an embodiment is that a larger area may be provided on the side facing the sensing element for improving its support and / or for saving plating material on areas where support is not required.

[0020] In some embodiments, the conductive member is a conductive planar member having a constant and uniform thickness outside the sensing region.

[0021] An advantage of embodiments of the present invention is that the lead frame can be easily made of a conductive plate, such as a metal plate.

[0022] In another aspect, the present invention provides a current sensor comprising the lead frame of an embodiment of the first aspect.

[0023] An advantage of embodiments of the present invention is that the current sensor withstands currents exceeding 50A and surge currents exceeding 20kA.

[0024] In another aspect, the present invention provides a method for manufacturing a lead frame of an embodiment of the first aspect, the method comprising providing a shaped conductive member having an average thickness. Additional material is provided on an area serving as a sensing area, so that the total thickness of the sensing area is thicker than the average thickness. Thus, the lead frame is divided on the sensing area and a routing area outside the sensing area, wherein the routing area has a maximum area and an average thickness thinner than the total thickness of the sensing area.

[0025] An advantage of embodiments of the present invention is that LF can be provided using conductive members (eg, metal sheets) having thicknesses that meet industry standards.

[0026] In some embodiments, the additional material is provided by additive manufacturing techniques.

[0027] The advantage is that highly customized shapes for specific applications can be provided in a relatively simple manner in a single manufacturing step.

[0028] In some embodiments, the additional material is provided by depositing a conductive material on the lead frame, for example by vacuum deposition and / or electroplating.An advantage is that multiple LFs can be produced in a single batch.

[0029] In some embodiments, the method further comprises providing a mask.An advantage is that complex shapes can be applied.

[0030] In another aspect, there is provided a method of providing a sensor, the method comprising providing a lead frame according to the previous aspect, the method further comprising attaching a die to the lead frame and providing molding.

[0031] An advantage is that the die requires no additional external support and can be connected to different frames via wire bonding or the like.

[0032] In some embodiments, the method further includes providing an insulating layer between the lead frame and the die. Advantageously, electronic devices in the die can be protected from current and surges passing through the lead frame.

[0033] In another aspect, there is provided a packaged sensor comprising a lead frame according to an embodiment of the first aspect of the invention.

[0034] Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims and with features of other dependent claims as appropriate and not just as explicitly set out in the claims.

[0035] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The figure shows a top view of a current sensor known in the art.

[0037] Figure 2 The figure shows a top view of a current sensor including a frame according to an embodiment of the present invention.

[0038] Figure 3 The diagram shows Figure 2 The cross section indicated in the top view of FIG. 1 shows the sensing element and the lead frame in the sensing area.

[0039] Figure 4 The diagram shows Figure 2 Different cross sections are indicated in the top view of the lead frame, thereby illustrating the routing area and the sensing area of ​​the lead frame.

[0040] Figure 5 The diagram shows details of the sensing area of ​​the lead frame and the semiconductor die, where the lead frame and SC die are attached to each other.

[0041] Figure 6 FIG. 2 shows an embodiment of the present invention Figure 2 Top view of the lead frame.

[0042] Figure 7 The figure shows a top view of a lead frame according to an embodiment of the present invention. The attachment layer and the SC die are also shown in a superimposed manner.

[0043] Figure 8 Shows Figure 7 The cross section indicated in .

[0044] Fig. 9 A manufacturing process flow for producing a lead frame according to an embodiment of the present invention is shown.

[0045] Fig.10A manufacturing process flow for producing a current sensor according to an embodiment of the present invention is shown.

[0046] These drawings are only schematic and non-limiting.In the drawings, the size of some of the elements may be exaggerated and not drawn to scale for illustrative purposes.

[0047] Any reference signs in the claims should not be construed as limiting the scope.

[0048] The same reference numbers in different drawings refer to the same or similar elements. DETAILED DESCRIPTION

[0049] The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims.The dimensions and relative dimensions do not correspond to actual reductions to practice of the invention.

[0050] Furthermore, the terms first, second, etc. in the specification and in the claims are used to distinguish between similar elements and are not necessarily used to describe a sequence in time, space, in ranking, or in any other manner. It should be understood that the terms so used are interchangeable under appropriate circumstances, and that the embodiments of the invention described herein are capable of operation in a sequence different from that described or illustrated herein.

[0051] Furthermore, the terms top, bottom, etc. in the description and claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in orientations other than those described or illustrated herein.

[0052] It should be noted that the term "comprising" used in the claims should not be interpreted as being limited to the means listed thereafter; it does not exclude other elements or steps. Thus, the term should be interpreted as specifying the presence of the stated features, integers, steps or components as mentioned, but does not exclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Therefore, the term "comprising" covers the case where only the stated features are present as well as the case where these features and one or more other features are present. Thus, the scope of the expression "a device comprising means A and B" should not be interpreted as being limited to devices consisting only of components A and B. It means that for the present invention, the only relevant components of the device are A and B.

[0053] References throughout this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification do not necessarily all refer to the same embodiment, but may. Furthermore, in one or more embodiments, as would be apparent to one of ordinary skill in the art from this disclosure, the particular features, structures, or characteristics may be combined in any suitable manner.

[0054] Similarly, it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. However, this method of disclosure should not be interpreted as reflecting an intention that the claimed invention requires more features than those expressly recited in each claim. On the contrary, as reflected in the appended claims, the inventive aspects lie in fewer features than all of the features of a single preceding disclosed embodiment. Thus, the claims appended to the Detailed Description are hereby expressly incorporated into the Detailed Description, with each claim itself representing a separate embodiment of the invention.

[0055] In addition, although some embodiments described herein include some features included in other embodiments but do not include other features included in these other embodiments, the combination of features of different embodiments is intended to fall within the scope of the present invention and form different embodiments as will be understood by those skilled in the art. For example, in the appended claims, any of the embodiments claimed for protection may be used in any combination.

[0056] In the description provided herein, numerous specific details are set forth. However, it should be understood that embodiments of the present invention may be implemented without these specific details. In other examples, well-known methods, structures, and techniques are not shown in detail to avoid confusion in understanding this description.

[0057] In embodiments of the present invention, when referring to a "substrate", it refers to an electronic platform, for example, a semiconductor platform including a sensing element, which is usually referred to as a "semiconductor die" or simply an SC die. The substrate includes an integrated circuit system, and it can be connected to a sensing element for sensing current, for example, to one or more magnetic sensing elements. The sensing element can be integrated in the same substrate, or stacked on top, or arranged next to the integrated circuit system.

[0058] In embodiments of the present invention, when referring to a "lead frame" or LF, it refers to a conductive structure designed to route a signal from one contact (usually called a "lead") to another contact (usually routed to a contact in a substrate). The lead frame is part of a semiconductor package and typically includes contacts that allow the transmission of signals from the outside of the package to the inside of the package. These contacts are specifically named "pins" in the art. The main LF in the integrated sensor carries the current to be sensed. Thus, it includes a sensing area that is configured so that the sensing element picks up the signal. The main LF also includes a routing area that brings the signal from the outside (from the pins) to the sensing area.

[0059] Figure 1 An integrated current sensor 10 is shown that is provided as a packaged sensor, wherein a sensing element 20 is typically provided in a substrate 11 (e.g., a semiconductor die). A current-carrying LF 15 ("main LF") is connected to a first external conductor 30 via an external pin 16 to introduce a current or a current to be tested from the conductor into a package 17 of the packaged sensor 10. The main LF routes the current to a region 14 next to the sensing element (sensing region), and then leaves the package again via another external conductor 31 connected in series to the pin, the LF 15, and the first conductor 30. The signals generated in the sensing element follow a different path from the main LF. These signals are output to the output pins 12 of the package via secondary leads. The secondary leads provide a power supply to the IC, and transmit an output signal (indicative of current) from the substrate to the output pins 12. The leads connected to the output pins 12 are typically included in the secondary LF 13 that is electrically connected to the substrate 11, for example, by a flip chip connection or wire bonding.

[0060] In order to get a large signal, the current to be tested preferably flows close to the sensing element. In some embodiments, the substrate is supported by the main LF, optionally by both the main LF and the secondary LF. In some embodiments, the substrate is not supported by the LF, for example, it can be positioned next to the LF optionally using a pre-molding device or the like. In some embodiments, the secondary LF, rather than the main LF, can be the support for the substrate.

[0061] The present invention mainly relates to the primary LF. In the following, when a LF is mentioned, it refers to the primary LF unless explicitly specified otherwise.

[0062] Conventional integrated current sensors have a tolerance of about 50A of stable current. However, integrated current sensors need to be able to withstand increasingly higher current demands to enable their use in novel applications. These applications include battery management systems for electric vehicles, solar energy collection systems (particularly solar inverters), etc., which require integrated current sensors with a current carrying capacity of 100A and / or a surge current of 20kA. However, the current carrying capacity of standard LF is limited.

[0063] The current capability is determined by the material and its geometry, which in turn is limited by design, manufacturing and compactness requirements. Industry standards for LF thickness often do not meet the requirements of these novel applications.

[0064] By thickness, it is understood to be the dimension of the LF in a direction perpendicular to the plane formed by the routing area and / or the sensing area. This plane is the plane in which the current to be tested flows. Thus, the thickness is perpendicular to the plane in which the current flows (thus the thickness is perpendicular to the general direction of the current).

[0065] LFs of standard thickness (250 microns) suffer thermal damage when subjected to such high currents and surges as mentioned above. They may also suffer mechanical damage due to heating and / or mismatch of the coefficient of thermal expansion (CTE) with the surrounding materials. Therefore, the industry is driven towards thicker LFs of the order of 500 microns. This greatly increases the cost due to the large amount of raw materials used in LF manufacturing and assembly, the non-standard and more complex tools required, etc. Increasing the width of the LF requires a larger spacing of the sensing elements, thereby degrading the signal, and this option can make the sensor less compact.

[0066] In a first aspect, the invention provides a LF formed of a conductive member having an average thickness, the LF comprising additional material locally disposed on an area of ​​the conductive member that is a sensing region. The added material provides protection against high currents and surges. For example, the LF may have an average thickness with locally increased thickness at the sensing region. This provides a more cost-effective LF for an integrated current sensor. The thickness increase is provided using, for example, electroplating, but other methods are also provided.

[0067] The additional material may be a material that is fused to the LF, thereby forming an integral part of the LF, such that it cannot be easily removed without, for example, cutting, grinding or destroying the additional material.

[0068] The total thickness is increased in the sensing region of the LF (e.g., in the bridge), which is typically the region closest to the sensing element. In some designs, the LF is configured so that the sensing region is also the region with the highest current density. This is the portion that may potentially suffer the most damage. Providing a larger thickness in this region helps protect the LF because the additional thickness on the sensing region, which is typically configured as the region with the highest current density, provides the LF with high thermal inertia and dissipation capabilities. Additionally, providing only a small portion of the lead frame with a larger thickness allows material savings and allows the LF to be provided using a standard sheet thickness.

[0069] In an embodiment of the present invention, the LF includes a narrowing or necking where the cross-sectional area is minimal. The necking reduces the passage area of ​​the current in a plane perpendicular to the thickness. The current is forced to pass through the necking. This increases the current density and therefore a stronger magnetic field generating a very high signal in the sensing element. In addition, the necking allows sensing elements (e.g., magnetic sensing elements) to be placed close to each other, allowing a more compact design and enabling a smaller substrate required to hold them.

[0070] Figure 2 A schematic top view of a current sensor 100 is shown, showing the direction of the current I entering the LF 101 through the pin 104 and into the sensor, and exiting the sensor. An LF with such a necking on the sensing area benefits from a larger thickness, which is located in the sensing area 200 next to the sensing element 20. The added material that provides the additional thickness is conductive, and it can be the same material as the rest of the LF, but it can also be a different conductive material. The sensing element may include a magnetic field sensing element that measures the magnetic field generated by the current through the LF 101, thereby providing a signal that depends on the current. The magnetic field is generated by the current through the LF, also in the sensing area 200. Since the sensing area 200 next to the sensing element has a local increase in current, the field generated by this part is large, and the sensing element is efficient in generating a signal based on the field.

[0071] Figure 3 and Figure 4 A cross section across the sensing element on the substrate and across the length of the LF is shown respectively. The substrate 21 may comprise the sensing element. The substrate may be supported, optionally attached to the LF 101. A layer of insulating material 18 may be provided between the LF 101 and the substrate 21. The layer 18 may also be an adhesive.

[0072] In some embodiments, the LF is a conductive plane or plate with uniform thickness outside the sensing area. Figure 4 . The additional thickness is locally added to the sensing area in the z-direction, for example to a narrow portion where the sensing area is defined. Since there is more material, the thermal inertia is increased without providing a larger width. The additional thickness does not significantly degrade the current field conversion ratio (because increasing the width of the LF in the x-direction is unnecessary). An advantage of the present invention is that the maximum current capability is increased without changing (increasing) the width of the conductor (for example, without removing or reducing the necking), which would require increasing the distance between the sensing elements to obtain the corresponding maximum signal. An integrated sensor with high sensitivity and high resilience against current surges can be obtained.

[0073] The increase in thickness may be provided in any suitable manner, for example, an additional layer 102 may be provided on one of the faces of the LF (e.g., in the face opposite to the substrate 21). One face is planar (so that the LF can support the substrate in a stable manner), while the other face includes a "bump" (the additional layer). The additional layer 102 may be provided on one of the faces of the LF (e.g., in the face opposite to the substrate 21). Figure 3 , shown with hatching, indicating the original thickness of the LF before providing additional layers.

[0074] Figure 5 An alternative LF 111 and a substrate for a semiconductor die 22 are shown. Figure 3 , the substrate includes a magnetic sensing element 20 (e.g., a magnetic sensing element with an integrated circuit for processing a signal generated by the sensing element). In some embodiments, for example, the integrated circuit can be arranged to obtain a signal indicating a difference between two sensing signals.

[0075] The invention is not limited to magnetic sensing elements integrated in the substrate. The sensing elements may be separate sensing elements connected to the substrate; for example, they may be stacked on a die. For example, sensing elements based on III-V semiconductor technology (based on, for example, silicon, the invention is not limited thereto) may be provided on a semiconductor die. For example, sensing elements based on magnetoresistive materials (xMR sensing) may also be stacked on a substrate.

[0076] The placement of the sensing elements relative to the conductor can be optimized to maximize the signal. In some embodiments, the sensing elements are placed on the periphery of the edge of the conductor, for example aligned with the edge. In some embodiments, they can be slightly inside the periphery of the conductor, or slightly outside the periphery of the conductor. For example, the center of the sensing element is located within a distance of + / -10%W or + / -20%W from the edge of the conductor, where W is the width of the conductor.

[0077] Figure 5 A die-up configuration is shown, with the active surface of semiconductor die 22 (the surface of the die that includes sensing element 20) facing away from the leadframe. However, the invention is not limited thereto, and other configurations (e.g., a flip-chip configuration) may be used, with the active surface of the substrate facing the leadframe.

[0078] One or more sensing elements may be selected based on the specific requirements of the sensor. In some embodiments, the magnetic sensing element has an axis of maximum sensitivity perpendicular to the substrate (e.g., a horizontal Hall sensor). In some embodiments, the magnetic field sensing element has an axis of maximum sensitivity parallel to the substrate, e.g., a vertical Hall plate, a magnetoresistive (MR) element, etc.

[0079] Both the die 22 and the LF 111 are in contact with and separated by a layer of insulating material 41. In this case, the layer of insulating material is shown to extend beyond the top area of ​​the LF. This advantageously improves insulation because it increases the discharge path between the current-carrying LF and the substrate having the sensing element. The layer of insulating material can cover the entire surface of the substrate facing the LF, thereby further improving insulation. In this LF 111, the thickness is increased by two additional layers 112, 113, one additional layer at each face of the LF. This overcomes some limitations on thickness inherent in certain manufacturing processes (e.g., deposition). Adding layers on each side allows the total equivalent thickness to be increased. Additionally, depositing a predetermined thickness on only one side typically takes longer than depositing half the thickness on each side of the LF.

[0080] Regarding added material, the additional thickness can be 5% or more of the average thickness of the LF, for example between 5% and 120% of the frame thickness, for example between 10% and 80% of the frame thickness, for example between 10% and 50% of the frame thickness, for example between 20% and 40% of the frame thickness, for example 30% of the frame thickness.

[0081] In some embodiments, for a lead frame thickness of 200 microns to 500 microns, such as about 250 microns, the thickness of the additional material can be, for example, 15 microns higher, such as 50 microns higher, such as 100 microns, such as 200 microns, such as up to 300 microns. In some embodiments, for example, 50 microns can be provided at each side, thereby obtaining a thickness of 100 microns of added material, or any other combination of added thicknesses.

[0082] Although the additional layer has been shown on the side opposite the substrate or on both sides, the additional layer may be on only one side of the substrate side of the LF. Any of these options may be applied, depending on the specific sensor requirements. For example, if the LF is exposed or partially exposed on the bottom side of the package (partial overmolding), as in the case of certain types of so-called "flat no-lead" packages, the package can remain flat on the bottom if additional material is provided on the substrate side.

[0083] The material for the additional layer can be any conductive material, such as a metal compatible with the material of the LF, for example, the same material as the LF. For example, the material of the additional layer can be composed of or include Cu, Ti, Au, Al, Ag, Ni, Zn, Sn or Cr, and this list is not exhaustive. For example, a material that can be easily provided by electroplating can be used. One or more additional layers can be provided on the LF so that there is a bond (such as chemical bonding, etc.) between the material of the (one or more) additional layers and the material of the LF, rather than simply bonding or otherwise adhering the layer to the LF. The transition between the layer and the LF can be gradual. The additional layer can be fused to the LF, and it can be a deposited layer, that is, provided by deposition (e.g., electroplating) or the like. This will be explained with reference to the method. The LF may include a fusion layer on one or both sides, for example, a deposited layer. The present invention is not limited to deposited layers, and layers added by other techniques such as additive manufacturing (e.g., 3D printing) can be used.

[0084] Figure 6 Shows Figure 2 100 . The LF comprises a sensing region 200 and a routing region 201 , which routes current between the pin 104 and the sensing region 200 . The additional thickness may be limited to the sensing region 200 , or even to only a portion of the sensing region 200 . The LF may have its largest area 105 outside the sensing region 200 , e.g. the routing region 201 has a largest area with an average predetermined thickness. The largest area is thinner than the sensing region. In other words, the (average) predetermined thickness of the largest area 105 in the routing region 201 is lower than the thickness in the sensing region 200 . For example, the LF (particularly the routing region) may have a uniform thickness outside the sensing region 200 , and the sensing region 200 is thicker than the uniform thickness. The larger thickness is included in the sensing region 200 . It is limited to a relatively small area compared to the rest of the LF 101 . The larger thickness is shown as a shaded area, which may contain additional material, e.g. Figure 3 and Figure 4 An additional material layer 102 (eg, a deposited additional layer) is shown in cross-section.

[0085] Figure 7 A top view of the LF 121 partially overlapped by the insulating layer 43 and the substrate 22 including the sensing element (not shown) is shown. The insulating layer 43 extends beyond the substrate 22 and over the LF 121, thereby increasing the discharge path between the LF and the substrate. This Figure 8 is shown in Figure 7 corresponds to the cross section shown in .

[0086] A top extension layer 123 is provided to increase the thickness of the LF at the sensing region 220. In fact, the top extension layer 123 extends beyond the bridge of the sensing region 220. It extends above the routing region 221. This ensures the stability of the overlying substrate 22 supported by the LF (and especially by the top extension layer 123).

[0087] For example, the top layer may extend above the LF so that 50% of the substrate area, or 80% of the substrate area, or 100% of the substrate area is supported. The top layer may even extend beyond the area of ​​substrate 22, such as Figure 7 and Figure 8 as shown in .

[0088] It should be noted that although the added top extension layer 123 extends over a portion of the LF outside the sensing region and thus into the routing region 221, it is still a small portion of the total area of ​​the LF. Thus, the thickness of the sensing region 220 is still higher than the thickness in the largest region 125 having a predetermined average thickness (e.g., uniform thickness).

[0089] Figure 8 Also shown is an optional layer 122 that extends only within the sensing region 220, thus covering an area smaller than the top layer 123. Thereby, the amount of conductive material used to create additional thickness can be reduced, while still increasing the thickness at the sensing region 220 and improving support. However, the optional layer in the face opposite to the substrate can also extend beyond the sensing region 220, for example, to an area smaller than the top layer 123, the same as the top layer 123, or larger than the top layer 123. As mentioned before, as long as the sensing region is thicker than the thickness of the largest area of ​​the routing area, the layer can be arranged on the side of the LF facing the substrate, or on the opposite side, or on both sides, for example where one layer is arranged on the top side, on a larger area (suitable for providing a flat support for the tube core) and one layer is arranged on the bottom side, on a smaller area (e.g., only the bridge) (thereby saving electroplating material).

[0090] In some embodiments, the LF may be provided as a planar metal foil (or generally, a thin sheet of conductive material) of uniform thickness, while only a small portion of its area may be thicker. This small portion corresponds to the sensing region 220, and optionally also to a small surrounding portion (thus forming the top added layer 123). Thus, the LF may be protected from high currents and surges, as the narrow portion of the LF will not fuse or suffer thermal damage above 50A. This is achieved with minimal increase in the amount of material required to produce it, and without the production costs required for thicker sheets.

[0091] In a second aspect, a method for manufacturing a lead frame according to the aforementioned aspect of the invention is provided.

[0092] The method includes providing a material form (eg, a sheet) having an average predetermined thickness, and locally increasing the thickness of the material form at an area to be placed next to a sensing element, thereby improving the dissipation of the piece when subjected to high currents and surges.

[0093] Fig. 9 A manufacturing method is schematically shown, the manufacturing method comprising optional steps. Providing (901) a shaped part may include providing a metal sheet having a uniform thickness. In some embodiments, it may also include providing a shaped part including a necking. For example, a lead frame tray may be provided, wherein a plurality of LFs may be obtained.

[0094] Adding (902) a layer for increasing thickness may be accomplished by deposition on the sensing region. Adding material may include adding molten material to the LF. The transition between the layer and the LF is gradual, so the thickness of the LF may be considered to increase due to the added layer of material. Adding a layer may include electrodepositing (903) a material (e.g., a conductive material).

[0095] The electroplating can be done in a plating line where silver plating is performed to achieve wire bonding. It will only require changing the electrolyte. Thus, providing a LF with additional thickness at the sensing area can be done in the same industrial line as the assembly of the integrated sensor. Alternatively, a vacuum-based deposition technique (904) can be provided for locally increasing the thickness. These can include atomic layer deposition (ALD), chemical vapor deposition (CVD), sputtering, evaporation, etc.

[0096] The electroforming / plating or sputtering methods allow batch processing (910), so that several LFs can be produced at the same time. These batch processes may include additional steps, such as, for example, providing a mask and depositing a conductive material. The mask may be provided by photolithography. The mask may be provided using a stencil (e.g., via stencil printing). The mask protects areas of the LF where no additional thickness is required. Thus, the mask may cover a large portion of the LF that is larger than the uncovered portion (e.g., at least a portion of the routing area).

[0097] Alternatively, sequential processes may be used, which allows fine tuning of the individual processes. Examples of these may include additive manufacturing techniques. For example, printing (905) such as 3D printing may be used to provide additional thickness positioned over the sensing region (perhaps extending partially over the routing region).

[0098] In one aspect, the invention provides a method for manufacturing a sensor. The method comprises providing a LF following the method of the previous aspect of the invention, and then providing a sensing die (including a sensing element) and arranging it so that it can sense the current through the LF. Optional steps may be performed, such as:

[0099] Providing electrical connections between the substrate with sensing elements (eg, integrated circuits) and the secondary LF provides an insulating layer between the LF and the die.

[0100] Then, molding may be provided for protecting the LF and electronics.

[0101] like Fig.10 The specific example shown in may include providing (1001) a lead frame tray, which may include a plurality of LFs, and providing (1002) a mask on the tray. A conductive material (typically a metal) is then deposited (1003), for example by electroplating, and the mask is then removed, thereby providing additional thickness over the sensing area by providing an additional layer over the sensing area. This may be performed in an industrial electroplating line typically used in the field of circuit assembly and packaging.

[0102] Optionally, an insulating layer may be provided (1004) between the LF and the substrate with the sensing element. A substrate comprising the sensing element is provided, the substrate optionally also comprising electronics, contacts etc. In a preferred embodiment, the substrate is a die attached (1005) to a lead frame, the die optionally being electrically insulated from the lead frame. In some embodiments, the insulating layer may be an adhesive material having insulating properties, so providing (1004) the insulating layer may be performed simultaneously with attaching (1005) the substrate to the LF. It is therefore possible to combine electrical insulation and attachment. However, these may be different steps, and an additional insulating layer may also be deposited on the LF and / or the substrate, followed by attachment of the substrate and the LF, for example by an additional adhesive. In particular, attachment is performed such that the sensing element is adjacent to a sensing region having an additional thickness.

[0103] The substrate is not only included in the device, but also a signal output can be provided by connecting the substrate to the secondary LF if necessary. This can be done by flip chip connection, wire bonding, etc. Then, molding 1006 can be provided. The manufacture of these steps as explained above can be done in batches, thereby providing many sensors at a time. After molding, singulation of the sensor can be provided (1007).

[0104] This is only an example and other processes may follow, such as using additive manufacturing techniques.

[0105] In one aspect, the invention provides a sensor comprising a lead frame according to an embodiment of the first aspect of the invention.

[0106] Different packaging options may be applied to the manufacture of the device.The lead frame may be obtained according to an embodiment of the second aspect.The sensor may be obtained according to an embodiment of another aspect.

[0107] In some embodiments, the sensor is a packaged sensor. The packaged sensor may include a molded substrate and a lead frame. The leads may extend outside the mold. The leads may not be exposed at the main surface of the package. For example, they may extend outward to form a Figure 2 The connecting pins 104 shown in FIG. For example, they can extend through the side of the package. They can be optional bent leads, such as a dual in-line package, or other types of packages (SOIC, TSSOP, etc.).

[0108] In other embodiments, the packaged sensor can be a flat package with exposed terminals. Optionally, the conductors can be exposed on a major surface of the package, such as at the bottom surface of the package. In some embodiments, the package is a leadless package. The terminals can be exposed at the bottom side of the package. For example, the lead frame can optionally be exposed at the bottom side of the package. In such cases, additional material can be provided on the side of the LF that is embedded in the molded component and faces the substrate, so the bottom side can still be planar.

Claims

1. A lead frame for a current sensor, the lead frame comprising: A conductive member having an average thickness, and a sensing area, and a routing area outside the sensing area, wherein the sensing area is used to generate a signal that can be detected by a current sensing element when current flows through the lead frame, and the routing area is used to route the current toward the sensing area, wherein the routing area includes a region with a maximum area, and the region with the maximum area has a predetermined average thickness, wherein at least the sensing area includes additional material disposed on the conductive member so that the total thickness of the lead frame at the sensing area is thicker than the average thickness of the maximum area.

2. The lead frame according to claim 1, wherein: The lead frame includes a constriction over the sensing region.

3. The lead frame according to claim 1, wherein: The average thickness of the largest area of ​​the routing region is 250 microns.

4. The lead frame according to claim 1, wherein: The thickness of the sensing region is between 5% and 120% thicker than the average thickness of the conductive element, for example, between 10% and 80% thicker than the average thickness.

5. The lead frame according to claim 1, wherein: The additional material is disposed over the sensing area and beyond the sensing area to an area in the routing area that is less than the maximum area of ​​the routing area.

6. The lead frame according to claim 1, wherein: The piece is a sheet comprising two opposing planar faces, wherein the additional material is provided on one or both faces of the sheet.

7. The lead frame according to any one of the preceding claims, wherein The additional material disposed on one face of the sheet covers a first area, and the additional material disposed on the opposite face covers a second area, wherein the first area is larger than the second area.

8. The lead frame according to claim 1, wherein: The conductive member is a conductive planar member having a constant and uniform thickness outside the sensing area.

9. A current sensor comprising a lead frame according to any one of the preceding claims.

10. A method of manufacturing a lead frame according to claim 1, the method comprising providing a shaped conductive member having an average thickness, and locally adding material on an area serving as a sensing region so that the total thickness of the sensing region is thicker than the average thickness of the rest of the conductive member, wherein the area of ​​the conductive member having the average thickness is larger than the sensing region.

11. The method according to claim 10, wherein: Local addition of material is provided by additive manufacturing technology.

12. The method according to claim 10, wherein: The local addition of material is provided by depositing an electrically conductive material on the lead frame, for example by vacuum deposition and / or electroplating.

13. The method of claim 12, further comprising providing a mask.

14. A method of providing a sensor, the method comprising providing the lead frame according to claim 10, the method further comprising attaching a die to the lead frame and providing molding.

15. The method of claim 14, further comprising providing an insulating layer between the lead frame and the die.

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