Method for encasing an electrical unit and electrical component

Abstract

Method for encasing an electrical unit (20), wherein the method comprises the following steps: - Connecting the electrical unit (20) to a leadframe (10), then - Encasing the electrical unit (20) with a first plastic material to form an inner mold body (30), such that a plurality of contacts (14, 15) of the electrical unit (20) protrude from the inner mold body (30), - Punching out the inner mold body (30) from the leadframe (10), - Forming an outer mold body (50) surrounding the inner mold body (30) from a second plastic material at least partially in the form of a cage structure (50), wherein the outer mold body (50) has a cage area with a number of spaced-apart struts or bars, each spaced away from the inner mold body (30).

Description

[0001] The invention relates to a method for encasing an electrical unit and to an electrical component manufactured using such a method.

[0002] Components can be used, for example, as sensors to measure accelerations or rotational rates, or other quantities such as rotating magnetic fields or currents, and to transmit the pre-processed measurement signals to a higher-level evaluation electronics or control system. Such components can, for example, consist of a populated circuit board on which various electrical or electronic components are located.

[0003] In known manufacturing processes, a populated circuit board is, for example, pressed into a thermoplastic housing, after which a cover is cast and cured or laser-etched. Different designs and manufacturing concepts exist for different types of components, particularly different types of sensors.

[0004] A particular disadvantage of the known designs is that the printed circuit board is located in a cavity. Diffusion of moisture can lead to migration, corrosion, and short circuits. It has been shown that customer-specific requirements regarding installation space cannot always be met. Furthermore, a shielding plate can only be produced with considerable effort. The highest sealing classes cannot typically be achieved. A wide variety of designs and manufacturing processes or equipment are required. Moreover, the known manufacturing processes involve significant design, qualification, and support costs.

[0005] DE 10 2009 026 804 A1 describes a method for manufacturing electronic components comprising the following steps: providing several inserts which are arranged together in a frame, populating the inserts with at least one electronic micro-component each, wherein each insert together with the at least one micro-component forms a unit, overmolding the units with a separate first coating to fix the at least one micro-component to the associated insert, separating the units from the frame after overmolding with the first coating, and overmolding the units with a second coating each.

[0006] DE 11 2010 003 624 T5 describes a method for manufacturing a component of a vehicle lock assembly, comprising the following steps: inserting an electrical subsystem with several circuit paths, each electrically connected to a common ground, into a mold; forming the electrical subsystem into a preformed part by a first forming process in which only the common ground is encapsulated by an insulating layer; and forming a housing component over the preformed part by a second forming process.

[0007] From US patent 2013 / 0 154 626 A1, a rotational detection device is known with a housing that is overmolded with a first plastic body encasing a printed circuit board, and which has a second plastic body that at least partially encasing the first plastic body, wherein the second plastic body may have discontinuities. With such a housing, stresses can occur due to differing thermal expansion between materials, which can, for example, distort measurements.

[0008] It is therefore an object of the invention to provide a method for encasing an electrical unit which, in particular, avoids at least one or more of the aforementioned disadvantages. It is further an object of the invention to provide an electrical component which has been manufactured using a method according to the invention.

[0009] This is achieved according to the invention by a method according to claim 1 and an electrical component according to claim 14. Advantageous embodiments can be found, for example, in the respective dependent claims. The content of the claims is incorporated into the description by express reference.

[0010] The invention relates to a method for encasing an electrical unit, wherein the method comprises the following steps: - Connecting the electrical unit to a leadframe, then - Encasing the electrical unit with a first plastic material to form an inner mold body, so that a plurality of contacts of the electrical unit protrude from the inner mold body, - Punching out the inner mold body from the leadframe, - Forming an outer mold body surrounding the inner mold body from a second plastic material, at least partially in the form of a cage structure.

[0011] In the inventive method, the electrical unit is completely enclosed by a typically chemically and mechanically stable plastic material. Corrosion, migration, and short circuits are not expected. Furthermore, ultrasonic welding of additional components can be used. Compared to prior art methods, fewer processes are required overall, which accelerates and simplifies the process.

[0012] By forming the outer mold body as a cage structure, a decoupling between the outer and inner mold bodies is advantageously achieved. This can help prevent stress on the inner mold body caused by the outer mold body. For example, protectors against static and dynamic forces can be incorporated, thus protecting the entire unit. In contrast to full forming with thermoplastics or, more generally, with the second plastic material, the advantage here is the decoupling of the two shells by a gap. Thermomechanical forces, for example, from a thermoplastic onto a thermoset and from there onto a sensor element, are largely prevented.

[0013] Preferably, the outer mold body only partially rests against the inner mold body and is partially spaced from it. This allows for advantageous decoupling to prevent the formation of stresses that could, for example, distort sensor measurements.

[0014] The outer mold body features a cage-like structure with a number of spaced-apart struts or bars, each set back from the inner mold body. This provides protection for the inner mold body, similar to a surrounding bicycle helmet. For example, if the outer mold body is subjected to impacts, these are not immediately transmitted to the inner mold body, thus preventing stress and associated measurement errors.

[0015] According to a preferred embodiment, a portion of the inner mold body that abuts the outer mold body is at least partially surface-treated before the outer mold body is applied, in particular by plasma treatment or laser treatment, to achieve a seal against the ingress of liquid. Such surface treatment closes any leak that might occur due to the design with a partially formed outer mold body, which could lead to the ingress of liquid. In this way, failure of the installed electrical or electronic components due to diffusing moisture is effectively prevented.

[0016] Furthermore, the integration of a shielding plate is particularly easy in the process according to the invention. In prior art processes, a considerably greater effort was required to reliably attach such a shielding plate. A shielding plate can, in particular, improve the interference immunity of electronics and / or sensors. The attachment of a shielding plate will be discussed in more detail below. It should be noted that a shielding plate is preferably encased in the first plastic material.

[0017] The term "connection" can refer to various processes, including press-fitting, soldering (such as hard or soft soldering), gluing, welding (such as ultrasonic welding, laser welding, or resistance welding), or sintering. During the connection step, the electrical unit is typically reliably connected to the leadframe for the remainder of the process, thus securing it within the leadframe. The leadframe may, for example, feature connector or crimp terminals. More generally, metal strips for external contacting may already be integrated into the leadframe.

[0018] The leadframe may have index holes and thus also serve as a transport and adjustment aid.

[0019] The electrical unit can be, for example, any electrical component suitable for performing any electrical functions.

[0020] Furthermore, a shunt resistor can be attached, which may, in particular, have a section made of manganin. This is a commonly used and proven resistive material that allows for reliable measurement of the current flowing through it by measuring the voltage drop across it. Instead of manganin, another resistive material, especially a different copper-nickel-manganese alloy, can also be used. The shunt resistor can be contacted at two points or at more points, for example, four. The latter allows for four-point measurement, which can be advantageous, for instance, when using a material that is not temperature-stable.

[0021] It should also be mentioned that the electrical unit or a printed circuit board can be fully enclosed using the method according to the invention, specifically by a chemically and mechanically stable thermoset material. No corrosion, migration, or short circuits are to be expected. This meets the highest requirements for mechanical and chemical resistance. A shielding plate can be produced without significant additional effort.

[0022] Furthermore, it should be mentioned that with the inventive method, a design for a neutral part can be defined, and only customer-specific overmolding variants need to be varied. This means significantly lower investment, fewer core processes, and high production volumes for the neutral part. Smaller assemblies can be manufactured cost-effectively. Qualification, design, and support efforts are reduced.

[0023] A populated printed circuit board is preferably used as the electrical unit. This can be, in particular, a circuit for measuring currents. The method has proven to be especially advantageous for such printed circuit boards. An integrated circuit (IC) can also be used, for example. In particular, this can be configured for a sensor.

[0024] The circuit board can be made of materials such as rigid, flexible, or ceramic.

[0025] A thermoset plastic material can be used as the first plastic material. This is particularly chemically and mechanically stable.

[0026] A thermoplastic material can be used as a second plastic material. It is easy to apply and has proven effective as an external protective coating.

[0027] If contacts need to be connected during the process, they can be joined to another element, especially a shunt resistor, by welding, brazing, ultrasonic welding, laser welding, bonding, soldering, sintering, and / or resistance welding. Such methods have proven effective for typical applications.

[0028] According to one embodiment, the step of connecting the contacts to the shunt resistor is performed after the step of sheathing with the first plastic material. Alternatively, the step of connecting the contacts to the shunt resistor can also be performed before the step of sheathing with the first plastic material.

[0029] According to a further training, at least one sensor is mounted on the electrical unit, and the process includes the following step before the step of encasing the electrical unit and the shielding plate with a first plastic material: - Covering the sensor with a protective material, in particular with a low-viscosity material, preferably with a glob-top material.

[0030] Such a design leads to a particularly advantageous additional protection of the sensor, which can thus be protected from chemical and / or mechanical damage.

[0031] In the first plastic coating step, one design ensures complete encapsulation, possibly excluding any protruding contacts. This has proven particularly effective because it provides exceptionally good chemical and mechanical protection.

[0032] The inner mold body is preferably connected to the leadframe after the first plastic material coating step by a number of inserted or anchored support ribs. This facilitates process control and ensures a defined position of the inner mold body.

[0033] For example, fixed support ribs, retractable support ribs, and designs without support ribs can be used. These will be discussed in more detail below.

[0034] An inserted support rib can be understood, in particular, as a support rib that can be completely removed from the mold body during die-cutting. An anchored support rib can be understood, in particular, as a support rib that is anchored in the mold body in such a way that a portion of the support rib always remains within the mold body.

[0035] According to one embodiment, a number of convex and / or concave contours are formed in the inner mold body. These can be used to adjust further components or, during the molding process, to fix the first mold body in a second mold tool, i.e., a mold tool for forming the outer mold body.

[0036] The contacts can advantageously each have a number of grooves. This facilitates handling and results in a better grip in surrounding structures. It also increases the creepage distance for any liquid that may penetrate.

[0037] The electrical unit can have a number of holes for anchoring it in the first plastic material. This improves the hold of the electrical unit in the first plastic material, preventing production defects.

[0038] During the encapsulation step with the second plastic material, a connector is preferably formed, which allows for the easy integration of a connection component. Inserts can also be embedded, enabling the use and easy processing of prefabricated elements.

[0039] During the coating step with the second plastic material, a rivet is preferably molded, particularly for connecting an additional component. This allows for easy attachment and alignment of the additional component.

[0040] According to further training, additional surface activation of the inner mold body can be carried out, especially before the step of coating it with the second plastic material. This leads to improved adhesion of the outer mold body to the inner mold body.

[0041] Suitable materials for the outer mold body, i.e., the second plastic material, include PA (polyamide), PBT (polybutylene terephthalate), hot melt, or PU (polyurethane). This coating with the second plastic material can be achieved primarily through injection molding or RIM molding.

[0042] It should be mentioned that, in particular, a step involving connecting at least one first contact and a second contact with a shunt resistor can also be performed. This can be done, in particular, before encasing with the second plastic material to form an outer mold body. This allows, for example, the advantageous design of a battery sensor.

[0043] According to further training, the process also includes the following step before the step of encasing the electrical unit with a first plastic material: - Attaching one of the shielding plates assigned to the electrical unit.

[0044] The shielding plate allows for better shielding, for example against electrical or electromagnetic interference.

[0045] According to one embodiment, the shielding plate is attached by a punching step performed before the electrical unit is connected to the leadframe. This allows for a particularly simple provision of the shielding plate, which can, for example, be manufactured as part of the leadframe.

[0046] The shielding plate can be designed as a molded part and attached to the electrical unit by pressing it in. This allows for separate manufacturing of the shielding plate and greater design freedom.

[0047] The shielding plate can be mounted parallel to the electrical unit. This can refer in particular to the respective extensions of the shielding plate or an electrical unit, which can be designed as a plate. This allows for a particularly advantageous shielding effect.

[0048] In an advantageous embodiment, the shielding plate can be designed as a tray that accommodates the electrical unit. This allows for multi-sided enclosure of the electrical unit. The tray can preferably be covered by a tray cover. This particularly advantageously achieves complete enclosure of the electrical unit. This provides particularly effective protection against electromagnetic radiation and other similar influences.

[0049] The invention further relates to an electrical component manufactured by a method according to the invention. All embodiments and variants described herein can be used with regard to the method. The outer mold body typically represents the component, optionally with protruding contacts.

[0050] Further features and advantages will be apparent to those skilled in the art from the exemplary embodiments described below with reference to the accompanying drawing. These show: Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8 to Fig. 9: possible states in a process, Fig. 10: a variation with pins positioned perpendicular to a circuit board, Fig. 11: a variation with only partial covering, Fig. 12: a variation with an additionally protected sensor, Fig. 13: the variation of Fig. 12 in a later procedural step, Fig. 14a, Fig. 14b: a version with only partial covering and integrated protectors, Fig. 15: a variation with a cover tray, Fig. 16: the variation of Fig. 15 in a side view, Fig. 17: the modification of Fig. 15 and Fig. 16 at a later stage of the proceedings, Fig. 18: the state of Fig. 17 in a side view, Fig. 19: a variation with additional support ribs, Fig. 20: the state of Fig. 19 in a side view, Fig. 21: a variation with embedded measuring resistor, Fig. 22: the variation of Fig. 21 in a top view.

[0051] Fig. Figure 1 shows an arrangement such as typically occurs at the beginning of a method according to the invention. It should be understood that a more general method is described first and only later, with reference to Fig. 14 the cage-like structure will be described.

[0052] An external leadframe 10 is arranged, in which index holes 11 are formed. The leadframe 10 serves for stabilization and transport, and can be easily gripped and moved by means of the index holes 11. The index holes 11 are particularly useful for transporting the leadframe 10 and for fine-tuning its position in a mold tool. The index holes allow for mechanical adjustment of the leadframe 10, and thus of the already assembled component or sensor, in the various fixtures and / or mold tools used in the process.

[0053] The leadframe 10 has dampbars 12, which stabilize the leadframe 10 and are also designed for attaching additional components. The dampbars 12 have fixing holes 13, which can be used to fix the leadframe 10 or other components. The fixing holes 13 are particularly useful for fixing the die-cut part in the overmold tool.

[0054] The leadframe 10 further comprises three terminals in the form of plug terminals 14, which serve as electrical contacts after completion of the manufacturing process. The leadframe 10 also has two shunt connection terminals 15, which serve to connect a shunt resistor. In addition, the leadframe 10 has an anchored support rib 16 and an inserted support rib 18. Their function will be discussed in more detail later. It should be understood that there may be none or multiple support ribs 16 and 18.

[0055] An electrical unit in the form of a printed circuit board 20 is connected to the leadframe 10. The printed circuit board 20 is attached to the connector terminals 14 and the shunt connection terminals 15, in this case by soldering. However, the other connection techniques described above, such as press-fitting, can also be used. This ensures a secure connection between the printed circuit board 20 and the leadframe 10.

[0056] To protect the circuit board 20 from electromagnetic interference, a shielding plate 45 is attached. This is arranged parallel to and above the circuit board 20.

[0057] Furthermore, a number of holes 24 are formed in the circuit board 20, which serve for fixing in a mold body described below.

[0058] In Fig. Figure 1 shows the assembled circuit board 20 within the leadframe assembly. Here, the circuit board 20 serves primarily as a wiring carrier for sensors and additional circuitry. For example, accelerometers and gyroscopes in any combination are possible. Magnetic field sensors and current sensors can also be used or manufactured. The additional holes 24 allow the circuit board 20 to be more securely anchored in the thermoset mold body described below.

[0059] The connector terminals 14 are preferably pre-cut in the leadframe 10. However, it is also possible to connect the leadframe 10 to the connector terminals 14 in a separate connection process.

[0060] The shielding plate 45 can be punched directly from the leadframe 10 or pressed into the circuit board 20 as a molded part.

[0061] The circuit board 20 is preferably pressed into the leadframe 10. However, other connection techniques, such as soldering and gluing, are also conceivable.

[0062] For non-odd-numbered connector terminals 14, molded connector terminals 14 can be attached. The connection between the leadframe 10 and the molded connector terminals 14 can be made by welding, soldering, gluing, or splicing, among other methods.

[0063] In addition to a parallel arrangement of the circuit board 20 with respect to the connector terminals 14, as shown in Fig. As shown in Figure 1, a vertical position can also be represented. This will be explained further below. Fig. 10 shown.

[0064] Fig. 2 shows the arrangement of Fig. Figure 1 shows a side view after pressing. It can also be seen that a sensor 6 and a number of electrical components 9 are arranged on the circuit board 20. These are applied to the circuit board 20 using SMD technology.

[0065] In Fig. Figure 3 shows the state after the application of a first mold body 30. The circuit board 20 is surrounded by the first mold body 30, which consists of a thermoset material. The first mold body 30 can also be referred to as the inner mold body. The first mold body 30 was produced by encasing the circuit board 20 with a thermoset material.

[0066] As in Fig. As can be seen in Figure 3, both the anchored support rib 16 and the inserted support rib 18 project into the first mold body 30. The anchored support rib 16 is designed such that it has a barb in the first mold body 20. Therefore, it is also referred to as "anchored." The inserted support rib 18, on the other hand, has no barb, so it can be easily and completely pulled out of the first mold body 30. The anchored support rib 16, however, always remains partially in the first mold body 30, and the portion lying outside the first mold body 30 can be broken off.

[0067] The first mold body 30 provides chemical and mechanical protection for the circuit board 20, particularly through its thermoset material, with only the connector terminals 14 and the shunt connection terminals 15 protruding from the first mold body 30.

[0068] As will be shown below, the two shunt connection terminals 15 are U-shaped, thus forming a connection from the circuit board 20 to an area next to the circuit board 20. As will also be shown below, this serves to connect a shunt resistor.

[0069] The assembled circuit board 20, as shown, has no contact with the outside world. It is completely encased in a thermoset material. This minimizes the risk of moisture or corrosive media affecting the circuit board 20 or the sensor. Mechanical stresses on the mounted components of the circuit board are low or negligible, since the coefficient of thermal expansion of the thermoset material is approximately the same as that of the circuit board 20 and the components mounted on it. Furthermore, the adhesion between the materials is very good.

[0070] The support ribs 16, 18 can be designed to be embedded or anchored. They serve to provide additional support against gravity-induced deflection of the mold body, which is only held on one side at the Dambar side. These ribs have no connection to the circuit board 20.

[0071] Fig. 4 shows the arrangement of Fig. 3 in a side view.

[0072] Furthermore, it can be seen that only terminals 14 and 15 protrude above the first mold body 30. It should be noted that the shunt connection terminals 15 can also protrude below the first mold body 30.

[0073] Fig. 5 shows the in Fig. Figure 4 shows a modified arrangement. In this case, two concave fixings 32 and two convex fixings 34 are formed in the mold body 30. The fixings 32 and 34 serve to anchor or fix the mold body 30 in a higher-level structure or to attach other components to the mold body 30. In particular, they provide the possibility of forming positive-locking connections with other components or higher-level structures, for example, to a mold tool for further encasing. For example, they serve to position and lock the thermoset mold body 30 in the thermoplastic overmold tool. The fixings 32 and 34 can also be referred to as contours. It should be noted that the fixings 32 and 34, or corresponding elements, can also be formed laterally, i.e., transversely to the plane of the paper. Fig. 5 can be trained.

[0074] Fig. Figure 6 shows the arrangement of Fig. Figure 3 shows the process after the first mold body 30 has been punched out of the leadframe 10. The circuit board 20 and the surrounding first mold body 30 are visible, with the connected terminals 14 and 15 protruding from the first mold body 30, which were originally part of the leadframe 10. As can also be seen, a small part of the anchored support rib 16 remains in the first mold body 30. The rest of the leadframe 10 is still visible on the outside.

[0075] As described above, the circuit board 20 has a number of anchor holes 24, which are no longer visible. These holes serve to better fix the circuit board 20 in the first mold body 30. Furthermore, a decoupling zone (not shown in detail) can be formed to the right of the first mold body 30. This zone allows for some movement between the terminals 14, 15 and the circuit board 20 or the first mold body 30. The decoupling zone has proven particularly advantageous during the ultrasonic welding of the shunt connection terminals 15 to a shunt resistor, as it prevents vibration coupling into the first mold body 30 that could potentially lead to delamination.

[0076] In the die-cut section, terminals 14 and 15 are now implemented as individual pins. If required, a programming pin can be provided, which will no longer be accessible after the final mold is created.

[0077] All terminals 14 and 15 can be fitted with beads to increase the creepage distance for moisture and to achieve better anchoring in the overmold.

[0078] According to one possible interpretation, a Fig. 6. A groove (not shown) is provided, which extends the creepage distance for moisture and allows better anchoring in a second mold body to be formed subsequently.

[0079] Based on the one in Fig. The state shown in 6 can be in Fig. A shunt resistor (not shown) is attached, which is referred to below as shunt resistor 40. In this case, shunt resistor 40 can be attached to the shunt connection terminals 15 by ultrasonic welding at weld points 42. Other connection techniques, as described above, can also be used. With this arrangement, a voltage can be measured that drops across shunt resistor 40 approximately equal to the width of the first mold body 30. This allows the current flowing through the shunt resistor to be determined.

[0080] Fig. 7 shows a state of the arrangement of Fig. 6 after the application of a second mold body 50. The second mold body 50 can also be referred to as the outer mold body. In this case, the second mold body 50 consists of a thermoplastic material and surrounds the circuit board 20 and the first mold body 30, as well as most of the shunt connection terminals 15, the connector terminals 14, and, if present, the shunt resistor 40 (not shown here). A shunt connection terminal 15, which is shown in the image above, has a slightly modified external contact, particularly compared to the one shown in Fig. 6 shown state.

[0081] The connector terminals 14 protrude from the second mold body 50, enabling electrical contact with the circuit board 20. Furthermore, if present, a first contact surface and a second contact surface of the shunt resistor 40 protrude from the second mold body 50 to allow the connection of external components. Other electrical units or an external circuit, for example, can be connected to these contact surfaces, allowing the circuit board 20 to measure the current flowing through the shunt resistor 40. Corresponding signals indicating such a current can be transmitted to other units via the connector terminals 14.

[0082] The final encapsulation of the thermoset-molded circuit board 20 is preferably carried out with a thermoplastic material.

[0083] In this step, a connector 56 is also formed. If required, further inserts, such as sleeves, swivel bearings, shunts, etc., can be embedded in the thermoplastic body.

[0084] It should be noted that it can also be seen here that the second mold body 50 contains an insert in the form of a fastening element 53. This allows, for example, attachment to other components.

[0085] Fig. Figure 8 shows the arrangement of Fig. 7 in a side view. For details on the individual features, please refer to the description above.

[0086] Furthermore, a rivet 52 for hot-stitching is provided on the underside of the second mold body 50. Additionally, a connector 56 is provided on the right, which allows for easy contacting of the connector terminals 14 and / or the shunt connection terminals 15.

[0087] A molded fixing nipple or mounting dome can also be provided.

[0088] The in the Fig. 7 and Fig. The finished arrangement shown in Figure 8, after completion of one possible embodiment of the method, can be referred to as an electrical component 5. This can be used in a higher-level component or in a unit such as a motor vehicle, in particular to measure a current.

[0089] Various pin configurations are possible for fixing the thermoset body or first mold body 30 in the overmold tool, which are shown schematically in Fig. 9 are shown. Fig. 9 is a variation of the execution according to Fig. 8 shown.

[0090] One option is to use a retractable support pin or support bar. It retracts automatically after the tool is closed. One possible result is in Fig. 9 with reference 32a.

[0091] A fixed support pin or support ridge can also be used. The support pin then replicates the contour in the overmold. One possible result is shown in Fig. 9 with reference 32b.

[0092] A version without a support pin or support ridge can also be used. The raised contour of the thermoset body then serves, for example, as a spacer in the overmold tool. One possible result is shown in Fig. 9 with reference 32c.

[0093] The previously mentioned fixing nipple 52 can also be used.

[0094] In Fig. Figure 10 shows a modified version in which the circuit board 20 is pressed in perpendicular to the connector terminals 14. This makes it possible, for example, to implement other sensing directions for sensors with sensing axes orthogonal to the measuring direction.

[0095] In Fig. Figure 11 shows a modification in which the thermoplastic casing, or the second mold body 50, is partially shaped to minimize the thermomechanical stress on the sensor element. As shown, the second mold body does not completely enclose the first mold body 30, but only partially.

[0096] In Fig. Figure 12 shows a modification from a state prior to the application of the first mold body 30, in which a coating 7 made of a low-viscosity material, in particular Globtop, was applied over the sensor 6. This serves in particular to protect the sensor against thermomechanical stress.

[0097] Fig. 13 shows the execution of Fig. 13 after remolding with the two mold bodies 30, 50, i.e., in particular as a finished component 5.

[0098] Fig. Figure 14a shows an embodiment of a finished component 5 in which the second mold body 50 does not completely enclose the first mold body 30, but rather only partially. Fig. Figure 14a shows a top view. Fig. 14b shows the state of Fig. 14a in a side view. This corresponds in particular to a method according to the invention.

[0099] In the respective right part of the Fig. 14a, Fig. In Figure 14b, the two mold bodies 30 and 50 are arranged directly adjacent to one another. An interface 59 is formed between the two mold bodies 30 and 50, which must be specially protected against the ingress of moisture. This will be discussed in more detail below.

[0100] In the respective left part of the Fig. 14a, Fig. 14b the second mold body 50 is formed in the form of protectors 58. These only partially enclose the first mold body 30, so that the first mold body 30 can still be seen.

[0101] The protectors 58 function similarly to a bicycle helmet, i.e., they protect the first mold body 30 from impacts and provide mechanical decoupling between the two mold bodies 30, 50. This effectively prevents the occurrence of mechanical stresses in the first mold body 30, which can lead to distorted measurement results, for example, in sensors. In particular, the occurrence of thermal stresses due to temperature changes can be prevented.

[0102] It should be noted that thermoset material is typically hard and brittle. To protect it against mechanical damage, it can be protected against static and dynamic forces by the protectors 58. These protectors 58 are designed in a U-shape, similar to a bicycle helmet, for example, and keep external forces away from the epoxy mold or the first mold body 30.

[0103] Unlike a full coating with thermoplastic, which is used, for example, in Fig. As shown in 7, this is during the execution of the Fig. 14a, Fig. 14b The advantage of decoupling the thermoset from the thermoplastic casing by means of a gap is given. Thermomechanical forces of the thermoplastic on the thermoset and from there on a sensor element are largely prevented.

[0104] A gap between protectors and thermoset housing is created, for example, by a special setting of the overmold process or by tooling.

[0105] Additionally, the exposed surfaces of the thermoset can serve to support the thermoset preform in the thermoplastic overmold tool.

[0106] In an adhesion zone, or interface 59, achieved through special surface treatment of the thermoset body, there is enhanced adhesion between the thermoplastic and the thermoset. This ensures that no corrosive or conductive materials or liquids penetrate the contact area of ​​the thermoset body and damage or short-circuit the electrical contact. The surface treatment or processing of a thermoset body, or more generally of the first mold body 30, can be carried out, in particular, by plasma treatment or laser treatment. This has proven effective in achieving the desired permanent seal.

[0107] It is advantageous if, as shown here, the circuit board 20 is mechanically and chemically protected in two molding steps.

[0108] In special applications, increased adhesion of the overmold to the thermoset mold can be achieved through additional surface activation of the thermoset body.

[0109] It is advantageous if the fully calibrated and tested sensors can be used as BGA or QFN packages (with and without additional internal circuitry). This allows for customer-specific circuitry on the printed circuit board 20 without increased effort. The connection technology is preferably soldered, as specified in the sensor design. Particularly, but not exclusively, in BGA versions, the thermoset mold can also be used as an underfill.

[0110] Another advantage is the production of a neutral part made of thermoset plastic, which can then be overmolded with a thermoplastic, thermoset plastic or elastomer according to customer specifications.

[0111] In one particular version, the plug can be replaced by a cable.

[0112] It is advantageous if the dimensions of the printed circuit board are standardized, as this allows the manufacturing facilities to be optimized for this format(s). This aligns with the strategy of IC manufacturers in defining the package shape.

[0113] In this context, it is advantageous if the leadframe acts as a holder, adjustment mechanism, and electrical contact point for the circuit board. This eliminates the need for the circuit board 20 itself to have a direct external connection. It is completely encased by the thermoset material, which has a coefficient of thermal expansion very close to that of the circuit board material. The only potential entry point for contamination is in the terminal area. However, these channels are effectively sealed because the thermoset material bonds with the leadframe materials.

[0114] In another configuration, the printed circuit board 20 can be replaced by one or more integrated circuits (ICs) which are connected to the leadframe using suitable techniques such as soldering, gluing, or welding. Additional circuitry such as capacitors can be mounted directly onto the leadframe terminals within the thermoset plastic.

[0115] The final overmolding materials, generally referred to as thermoplastics in this text, are typically PA, PBT, hot melt, or PU. The final encapsulation can typically be achieved through injection molding or RIM molding.

[0116] It should be noted generally that this description frequently refers to a thermoset, a thermoset material, or a thermoset composite for the inner mold body, and likewise to a thermoplastic, a thermoplastic material, or a thermoplastic composite for the outer mold body. This refers only to the embodiment currently considered most suitable. It should be understood that these terms can, in principle, be generalized, in particular to more general plastic materials or, more generally, materials or mold bodies. The disclosure of this application fully comprises a corresponding modification, extension, or generalization.

[0117] The Fig. Figure 15 shows an alternative embodiment in a process stage prior to the application of the first mold body 30, wherein a shielding tray 45 is used instead of a simple shielding plate. The shielding tray 45 can be, as shown in Fig. 15 shown, in particular formed with the leadframe 10, wherein the circuit board 20 is inserted into the formed shielding tray 45 or is introduced in another way.

[0118] Fig. Figure 16 shows a side view of the in Fig. Figure 15 shows the state. The shielding tray 45 is visible in its tray-like shape. The shielding tray 45 is covered by a lid 46. This ensures complete enclosure of the circuit board 20 and thus particularly effective protection against electromagnetic interference.

[0119] Furthermore, it can be seen that circuit board 20 and shielding tray 45 are connected to each other by means of a fastening pin 47. This ensures a stable mechanical and electrical connection between shielding tray 45 and circuit board 20.

[0120] Fig. 17 shows the execution of Fig. 15 and Fig. 16 after the application of the first mold body 30.

[0121] Fig. 18 shows the state of Fig. Figure 17 shows a side view. It should be noted that the lid 46 is not shown.

[0122] It should be noted in general that in one form of the idea of ​​the molded shielding plate, the shielding plate is designed as a tray or shielding tray.

[0123] This option offers the following advantages.

[0124] Regarding the manufacturing process, it should be mentioned that the leadframe 10 can be stamped and formed so that shielding trays 45 can be continuously manufactured in the leadframe assembly, into which the fully assembled and aligned circuit board 20 can be inserted and contacted.

[0125] This intermediate product can now be die-cut or molded in a leadframe assembly, preferably using thermoset molding material. Depending on the design and requirements, the shielding tray 45, for example, can be filled with molding material only on the inside or it can be completely encased.

[0126] The shielding tray 45 may also contain fastening elements.

[0127] The tray shape is particularly advantageous for high-frequency (HF) assemblies when effective and efficient protection against interference reception and emission is required. Conveniently, this module, with the shielding tray 45, can be screwed to a metal surface on the outside, which then provides shielding for the second half.

[0128] Fig. Figure 19 shows a modification of the state of Fig. 3, with additional support ribs 15b provided which support the first mold body 30. This further increases the stability.

[0129] Fig. 20 shows the state of Fig. Figure 19 shows a side view. It can be seen that vertical parts of the additional support ribs 15b, which are designated with the reference numeral 15b, are connected to the shunt connection terminals 15. If these are connected to a shunt resistor, which will be described in more detail below, the vertical parts 15b can thus establish a connection between the shunt resistor and the circuit board 20, while the shunt resistor can also be contacted from the outside via the shunt connection terminals 15.

[0130] Furthermore, the execution of Fig. 20 components 22 are mounted above the circuit board 20.

[0131] Fig. Figure 21 shows a side view of a finished component 5 with separate protectors. It can be seen that in the right part, the first molded body 30 and the second molded body 50 abut each other directly at the interface 59, while in the left part, a gap 51 is formed between the first molded body 30 and the second molded body 50. The gap 51 effectively prevents the formation or transmission of stresses that could distort measurement results.

[0132] Furthermore, the execution according to Fig. Figure 21 shows a shunt resistor 40, which is embedded below the circuit board 20 in the second mold body 50, but not in the first mold body 30. This shunt resistor 40 can, in particular, be a temperature-independent, for example, temperature- and / or long-term stable reference resistor, which is used for measuring a current, especially a battery current. It is particularly advantageously mechanically stabilized and protected by the embodiment shown.

[0133] Fig. 22 shows a top view of the in Fig. Figure 21 shows the state. It can be seen that a first contact area 44 and a second contact area 46 are formed on the shunt 40 laterally to the first mold body 30. This allows the shunt to be connected to lines or cables that carry a current to be measured.

[0134] In the finished component, the shunt 40 is connected in particular to the shunt connection terminals 15.

[0135] In general, the shunt resistor 40 can also be described as an insert with an electrical function, which can be connected to the circuit board 20 via the terminals 15 through the front exit or via the alternative terminals or vertical parts 15b through the side exit. This part can also be omitted, leaving only a cage-structured overmold or a second mold body 50.

[0136] The cage structure of the second mold body 50 is advantageous for stress-sensitive components, such as sensors, because it prevents a force-fit connection locally in the sensor area. Shear, tensile, or shear stresses caused by thermomechanical strain or shrinkage, for example, post-crystallization of semi-crystalline thermoplastics, are not transferred to the thermoset mold body 30. The sensor embedded therein is not, or only minimally, exposed to external stress.

[0137] It should be understood that this application generally discloses in particular the following combinations: - Without cage and without electrical insert (especially standard encapsulation of a printed circuit board) - With cage and without electrical insert (especially sensor encapsulation) - Without cage and with electrical insert (especially current sensor with standard housing) - With cage and with electrical insert (especially current sensor with stress-decoupled encapsulation)

[0138] The formation of cage structures can be achieved through sliders installed in the tool or through targeted surface activation and non-activation.

Claims

[1] Method for encasing an electrical unit (20) wherein the method comprises the following steps: - Connecting the electrical unit (20) to a leadframe (10), then - Encasing the electrical unit (20) with a first plastic material to form an inner mold body (30), such that a plurality of contacts (14, 15) of the electrical unit (20) protrude from the inner mold body (30), - Punching out the inner mold body (30) from the leadframe (10), - Forming an outer mold body (50) surrounding the inner mold body (30) from a second plastic material at least partially in the form of a cage structure (50), wherein the outer mold body (50) has a cage area with a number of spaced-apart struts or bars, each spaced away from the inner mold body (30). [2] Method according to claim 1, wherein the outer mold body (50) only partially abuts the inner mold body (30) and is partially spaced away from the inner mold body (30). [3] Method according to one of the preceding claims, wherein a part of the inner mold body (30) adjoining the outer mold body (50) is at least partially surface-treated before the outer mold body (50) is applied in order to achieve a seal against the ingress of liquid. [4] Method according to one of the preceding claims, wherein a populated printed circuit board or an integrated circuit is used as the electrical unit (20). [5] Method according to any of the preceding claims, wherein the first plastic material is a thermoset material; and / or wherein the second plastic material is a thermoplastic material. [6] Method according to one of the preceding claims, wherein at least one sensor (6) is mounted on the electrical unit, and the method comprises the following step prior to the step of encasing the electrical unit (20) with a first plastic material: - Covering the sensor with a protective material (7). [7] Method according to one of the preceding claims, wherein in the coating step the first plastic material is completely coated. [8] Method according to one of the preceding claims, wherein the inner mold body (30) is connected to the leadframe (10) by a number of anchored or inserted support ribs (16, 18) after the step of coating with the first plastic material. [9] Method according to one of the preceding claims, wherein a number of concave and / or convex contours (32, 34) are formed in the inner mold body (30). [10] Method according to any of the preceding claims, wherein the first contact (15), the second contact (15) and / or a number of further contacts (14) each have a number of beads. [11] Method according to one of the preceding claims, wherein the electrical unit (20) has a number of holes (24) for anchoring in the first plastic material. [12] Method according to one of the preceding claims, wherein in the step of coating with the second plastic material a plug (56) is formed and / or inserts (54) are embedded. [13] A method according to one of the preceding claims, which further comprises the following step prior to the step of encasing the electrical unit (20) with a first plastic material: - Attaching one of the shielding plates (45) associated with the electrical unit (20), - wherein the shielding plate (45) is also encased in a first plastic material during the step of encasing the electrical unit (20). [14] Electrical component (5) produced by a method according to one of the preceding claims, wherein the outer mold body (50) represents the component (5).

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