A method for manufacturing a semiconductor device, a semiconductor device, a lead frame structure and a moulding form

Abstract

According to the first aspect, a method for manufacturing a semiconductor device is provided. The method provides a lead frame structure comprising an outer frame, an at least one lead frame die pad, an at least one lead frame terminal, and a plurality of lead frame junctions; b) mounting an at least one semiconductor die on the at least one lead frame die pad; c) mounting an at least one connecting element for creating electrical connection between the at least one semiconductor die and the at least one lead frame terminal; d) placing the lead frame structure, the at least one semiconductor die and the at least one connecting element in a molding form wherein the molding form comprises a breaking means for pressing and interrupting through the plurality of lead frame junctions; e) encapsulating by a mold compound the lead frame structure with the at least one semiconductor die and the at least one connecting element, such that at least part of the at least one lead terminal is exposed and thereby forming an encapsulated semiconductor device; f) interrupting, simultaneously with the encapsulation step in the molding form, the plurality of lead frame junctions in the lead frame structure between the at least one lead frame die pad and the at least one lead frame terminal by a pressing movement of the breaking means of the molding form locally through the plurality of lead frame junctions.

Description

[0001] TITLE

[0002] A method for manufacturing a semiconductor device, a semiconductor device, a lead frame structure and a moulding form

[0003] TECHNICAL FIELD

[0004] The present disclosure relates to a semiconductor device, a method of manufacturing the semiconductor device, a lead frame structure and a moulding form for use in this method. In particular, this disclosure relates to a semiconductor power packaging comprising the semiconductor device.

[0005] BACKGROUND OF THE DISCLOSURE

[0006] Power semiconductor packaging provides high conversion efficiency and is extensively utilized in applications demanding superior efficiency, such as automotive and industrial systems. Conventionally, this power semiconductor packaging comprises semiconductor dies mounted on a ceramic substrate. One site of the ceramic substrate is suitable for semiconductor dies attachment and second site of the ceramic substrate is suitable for connecting with a heat sink. Commonly, heat sinks are baseplates or coolers. The heat produced by the semiconductor dies is conducted through the ceramic substrate and the heat sink before being dissipated into the cooling liquid.

[0007] Semiconductor power packages are fabricated as layered structures comprising semiconductor devices with semiconductor dies, die pads, external connectors, connectors and a mold compound. Typical semiconductor devices comprise semiconductor dies attached to a lead frame, connected connectors for electrical connections and are further encapsulated to form a packaged semiconductor device.

[0008] Common ceramic substrate has a layered structure and comprises three layers, where a middle layer is a ceramic layer, a top layer is a copper circuited layer on which semiconductor dies are mounted and a bottom layer which is a copper layer connected to the heat sink. The ceramic layer comprises compounds such as AI2O3 (aluminium oxide), SiaN4 (silicon nitride) and AIN (aluminium nitride). In the state of the art, ceramic layers are commonly used as an insulation for the semiconductor power packaging and support for semiconductor dies. Conventional power modules utilize ceramic insulation materials, such as Direct Bonded Copper (DBC) and Active Metal Brazed (AMB) substrates where copper layers are bonded to each surface of the ceramic layer. These materials offer essential electrical insulation and mechanical support but substantially increase the overall cost of the power modules. AMB substrate comprises the top layer being a copper layer, the ceramic layer, two layers of brazing alloy and the bottom layer which is the copper layer.

[0009] Ceramic substrates are characterized by high thermal conductivity, excellent copper electrical conductivity, and excellent insulation properties. The superior electrical conductivity of copper facilitates the handling of high current flow, while the dielectric properties of ceramic substrates ensure the high isolation necessary for densely packed circuits in power modules. Reliable insulation is a critical requirement in semiconductor power packaging.

[0010] The conventional method of producing power modules uses the ceramic substrate for isolation purposes. Disadvantages of incorporating a ceramic layer include the high cost of high-thermal-conductivity ceramic materials, significant CTE (Coefficient of Thermal Expansion) mismatch between ceramic and copper, and a longer thermal dissipation path due to the presence of multiple layers made from different materials. Another issue is that it is difficult to cut lead frame junctions after the encapsulation process, as they are completely covered by the encapsulation material.

[0011] One approach is to remove the ceramic layer from the ceramic substate leaving copper layers and to mount semiconductor die directly on the lead frame being the top copper layer. Upon removal of the ceramic layer, the bottom copper layer is also removed, leaving only the top copper layer. In a single switch case, the semiconductor die is connected by tiny lead frame junctions which will not be covered by the encapsulation and can be cut out in the following process of trimming. However, in more complex configuration such as a half-bridge, the problem with separated semiconductor pads and / or terminals occurs. In typical solution, these separated / floating elements are supported and aligned in positions by the ceramic layer. After the ceramic layer is removed, these elements become either free-standing and lack support during the assembly process or need to be connected with adjusted elements. To overcome this issue, it is possible to use connections between these floating parts. However, a problem arises with how to remove these connections that are fully covered by a mold compound in a final step of encapsulation.

[0012] Document US11476179B2 discloses a transistor package comprising: a substrate; a first transistor in thermal contact with the substrate, wherein the transistor comprises a gate; the substrate sintered to a heat sink through a sintered layer; an encapsulant that at least partially encapsulates the first transistor; and a Kelvin connection to the transistor gate. It comprises a ceramic insulation layer.

[0013] SPM55 series is a power module developed to provide a minimized package and low power consumption with improved reliability. There is applied a new 600 V gate-driving high-voltage integrated circuit (HVIC), a new insulated-gate bipolar transistor (IGBT) of advanced silicon technology. It discloses copper traces connected to a main lead frame and it comprises an insulation layer.

[0014] There is a need to address the disadvantages associated with semiconductor device and associated methods of manufacturing

[0015] Accordingly, it is a goal of the present disclosure to provide a method for manufacturing a semiconductor device without the insulation layer as a support layer for semiconductor dies enhancing thermal and electrical performance as well as such semiconductor device

[0016] SUMMARY OF THE DISCLOSURE

[0017] According to a first example of the disclosure, the object of the present disclosure has been achieved by providing a method for manufacturing a semiconductor device, the method comprising: a) providing a lead frame structure with a first lead frame surface and an opposite second lead frame surface, where the lead frame structure comprises: an outer frame, an at least one lead frame die pad, an at least one lead frame terminal, and the plurality of lead frame junctions which are suitable for locally interconnecting the at least one lead frame die pads, the at least one lead frame terminal and the outer frame, b) mounting an at least one semiconductor die on the at least one lead frame die pad, c) mounting an at least one connecting element for creating electrical connection between the at least one semiconductor die and the at least one lead frame terminal, d) placing the lead frame structure, the at least one semiconductor die and the at least one connecting element in a molding form, wherein the molding form comprises a breaking means for pressing and interrupting through the plurality of lead frame junctions, e) encapsulating by a mold compound, using the molding form, the lead frame structure with the at least one semiconductor die and the at least one connecting element, such that at least part of the at least one lead terminal is exposed and thereby forming an encapsulated semiconductor device, f) interrupting, simultaneously with the encapsulation step in the molding form, the plurality of lead frame junctions in the lead frame structure between the at least one lead frame die pad and the at least one lead frame terminal by a pressing movement of the breaking means of the molding form locally through the plurality of lead frame junctions.

[0018] Providing the step of interrupting ensures effective removal of the connection between the at least one lead frame die pad and / or the at least one lead frame terminal covered by the mold compound. The method removes the necessity for the ceramic layer, which brings certain disadvantages to the semiconductor device. This feature further ensures a simplified and integrated process, characterized by lower costs by removing the ceramic layer. The solution eliminates the need to provide support for floating elements, as it ensures connections within the lead frame structure. The solution provides the ability to use an existing moulding form and its retractive moulding pins.

[0019] Preferably, step f) of interrupting the plurality of lead frame junctions is by a pressing movement of the breaking means of the molding form locally through the mold compound and through the plurality of lead frame junctions Preferably, the breaking means in the step f) move out from the molding form, press the plurality of lead frame junctions to interrupt interconnection between the at least one lead frame die pad and the at least one lead frame terminal, interrupt through the plurality of lead frame junctions, move back to the molding form, preferably the mold compound fills gaps received after interrupting the plurality of lead frame junctions. There is provided the encapsulated semiconductor device with an even layer of the mold compound without any gaps or openings.

[0020] Preferably, the breaking means are retractive molding pins suitable for pressing and interrupting the plurality of lead frame junctions. This feature enables a use of standard retractive moulding pins available in a moulding form to expand their functionality. In addition to pressing the placed lead frame structure and ensuring tight contact between the mold chase and the lead frame structure, it also facilitates cutting the lead frame junctions during the encapsulating step.

[0021] Alternatively, the breaking means comprises an ending suitable for being in contact with the plurality of lead frame junctions, preferably the ending is flat or sharp.

[0022] Preferably, the breaking means are rotatable. The rotating motion enhances the cutting / interrupting effect.

[0023] In a further example, step f) is followed by a step f 1 ) of trimming, using a trimming tool, residual material from the exposed parts of the lead frame structure.

[0024] In a further example, step f) is followed by a step f2) of mounting a heat sink component to the second lead frame surface. Such a connection provide the transfer of generated heat from the lead frame structure to the heat sink.

[0025] According to the second aspect of the disclosure, there is provided a semiconductor device as manufactured in accordance with the method according to the disclosure.

[0026] According to the third aspect of the disclosure, there is provided a lead frame structure for use in a method according to the disclosure comprising an outer frame, an at least one lead frame die pad, an at least one lead frame terminal, and the plurality of lead frame junctions which are suitable for locally interconnecting the at least one lead frame die pad, the at least one lead frame terminal and the outer frame.

[0027] Preferably, the plurality of lead frame junctions are thinner than the lead frame die pads and the lead frame terminals.

[0028] According to the fourth aspect of the disclosure, there is provided a molding form for applying a mold compound over a lead frame structure for use in a method according to the disclosure, comprising a mold chase comprising an upper mold chase with an upper cavity and a lower mold chase with a lower cavity suitable for enclosing the lead frame structure, a gate suitable for transferring the mold compound into the mold chase, and further the mold chase comprises a breaking means suitable for pressing and interrupting through the plurality of lead frame junctions within the lead frame structure locally by a pressing movement, wherein the pressing movement is driven by a movement system mounted in the molding form.

[0029] Providing the moulding form with the breaking means ensures the effectiveness of the method disclosed, where the breaking means, designed to correspond to the lead frame junctions, are suitable for interrupting them simultaneously during the encapsulating step.

[0030] Preferably, the breaking means are retractive molding pins suitable for pressing and interrupting lead frame junctions.

[0031] Preferably, the mold chase comprises the breaking means in a way suitable for moving out from the mold chase, pressing the plurality of lead frame junctions, interrupting through the plurality of lead frame junctions and moving back to the mold chase, preferably the upper mold chase and / or the lower mold chase comprises the breaking means.

[0032] Preferably, the breaking means comprises an ending suitable for being in contact with the plurality of lead frame junctions, preferably the ending is flat or sharp. Alternatively, the breaking means are rotatable. The rotating motion enhances the cutting / interrupting effect.

[0033] In a further example, the lower cavity and / or upper cavity is flat and / or comprises protruding structures arranged for interacting with the breaking means.

[0034] In a further example, the mold chase comprises an at least one pin suitable for pressing the lead frame structure, preferably the at least one lead frame die pad and / or the at least one lead frame terminal, preferably the upper mold chase and / or the lower mold chase comprises the at least one pin. They prevent a leakage of mold compound beneath the lead frame, which could cause overmolding issues.

[0035] BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The disclosure will now be discussed with reference to the drawings, which show in:

[0037] Figure 1 shows a semiconductor device in top view from a first lead frame surface with mounted semiconductor dies and connectors,

[0038] Figure 2 shows the semiconductor device in top view from a first lead frame surface and in cross section during an encapsulation process by a molding form with a breaking means,

[0039] Figure 3 shows the semiconductor device in top view and in cross section with a mold compound,

[0040] Figure 4 shows the semiconductor device in cross section with the breaking means cutting out lead frame junctions from a lead frame structure,

[0041] Figure 5 shows three embodiments of thicknesses of lead frame junctions in lead frame structures.

[0042] DETAILED DESCRIPTION OF THE DISCLOSURE

[0043] For a proper understanding of the disclosure, in the detailed description below corresponding elements or parts of the disclosure will be denoted with identical reference numerals in the drawings.

[0044] Figure 1 depicts an example of a lead frame structure 1 for use in the method according to the disclosure. The lead frame structure 1 has two surfaces: a first lead frame surface 1a and an opposite second lead frame surface 1 b. The lead frame structure 1 comprises an outer frame 2, an at least one lead frame die pad 3a, 3b, an at least one lead frame terminal 4a, 4ba and the plurality of lead frame junctions 6. The plurality of lead frame junctions 6 are suitable for locally interconnecting the at least one lead frame die pads 3a, 3b, the at least one lead frame terminal 4a, 4b and the outer frame 2 and they prevent any displacement during an encapsulation step.

[0045] The lead frame structure 1 is usually a metallic framework, often composed of copper or its alloys. The lead frame structure 1 is designed to support a semiconductor die and establish a conductive pathway between the semiconductor die and external circuits. The lead frame junctions 6, typically integral to the lead frame structure 1 , are generally made from the same material.

[0046] The disclosure distinguishes between two types of the lead frame die pads 3a, 3b and the lead frame terminals 4a, 4b, identifying the lead frame die pads 3a and the lead frame terminals 4a as floating (upon removal the ceramic layer) and the lead frame die pads 3b and the lead frame terminals 4b interconnected by the plurality of lead frame junctions 6. In one example, it may occur that both types are present while in another example, only the floating lead frame die pads 3a and / or the floating lead frame terminals 4a are present. This disclosure provides in each example connection of all aforementioned types using the plurality of lead frame junctions 6.

[0047] The goal of the disclosure is to remove the ceramic layer in the manufacturing method of the semiconductor packaging and to overcome issue of connections between the lead frame structure 1 and floating lead frame die pads 3a and / or lead frame terminals 4a. By removing this layer, the stabilization of these elements is lost, and thus additional lead frame junctions 6 are provided to prevent any displacements of floating lead frame die pads 3a and / or lead frame terminals 4a. To make it easier to distinguish the individual parts, floating elements are marked with the number 3a and 4a.

[0048] According to the first aspect of the disclosure, there is provided a method for manufacturing the semiconductor device solving a problem of removing the fully covered lead frame junctions 6 during the encapsulation step. An example of the method according to the disclosure is shown in Figures 1-4.

[0049] In a first step a) of the method according to the disclosure the lead frame structure 1 as described above is provided. The provided lead frame structure 1 , according to this example, comprises one floating lead frame die pad 3a and two floating lead frame terminals 4a, both are interconnected by the lead frame junctions 6 to the outer frame 2. Further, the provided lead frame structure 1 comprises one non-floating lead frame die pad 3b and two non-floating lead frame terminals 4b. A plurality of lead frame junctions 6 are provided for interconnection of certain parts of the lead frame 1. In this example, the lead frame terminals 4a, 4b comprise protruding parts being an uncovered lead frame terminal 7. This example comprises two the lead frame terminals 4a, 4b with the uncovered lead frame terminal 7 as it is depicted in Figure 1 .

[0050] In a second step b) of the method an at least one semiconductor die 8 is mounted at the at least one lead frame die pad 3a, 3b such that semiconductor dies 8 are electrically isolated from one another. Figure 1 depicts six of the semiconductor dies 8 mounted on the lead frame die pads 3a, 3b. The semiconductor die 8 has a first die surface suitable for being attached to the lead frame die pad 3a, 3b and a second die surface suitable for attaching an at least one connecting element 9 for an electrical connection.

[0051] The semiconductor dies 8 are attached to the lead frame die pads 3a, 3b of the lead frame structure 1 using well-known methods, such as soldering, eutectic bonding, epoxy adhesion, UV curing, sintering, or diffusion. Accurate alignment of the semiconductor dies 8 is crucial to ensure high process productivity, reliability, quality, efficient electrical signal transmission and effective heat management.

[0052] In a third step c) of the method the at least one connecting element 9 is mounted for creating electrical connection between the at least one semiconductor die 8 and the at least one lead frame terminal 4a, 4b. The connecting elements 9 are depicted in Figure 1. The connecting elements 9 may be wire bonds, bond clips, or any similar means that facilitate current conduction while establishing both electrical and mechanical connections between the semiconductor dies 8 and the lead frame terminals 3a, 3b. Wire bonds are thin wires, commonly made of gold or copper. These connections are crucial for ensuring optimal performance and preserving signal integrity.

[0053] In a fourth step d) of the method the lead frame structure 1 , the at least one semiconductor die 8 and the at least one connecting element 9 are placed in a moulding form. A mold compound 10 covering the structure is manufactured in the moulding form. Only uncovered lead frame terminals 7 and / or any other possible part suitable for external connection extend beyond the mold compound 10. A custom moulding form is created for each semiconductor device to accommodate the specific parts of the semiconductor device. This disclosure provides utilisation of the moulding form comprising a breaking means 11 suitable for pressing and interrupting through lead frame junctions 6 within the lead frame structure 1 covered by the mold compound 10. Particularly, the lead frame junctions 6 between the at least one lead frame terminal 4a, 4b and / or the at least one lead frame die pad 3a, 3b.

[0054] Typically, the moulding form comprises a mold chase 5 which is designed as a two-part mold chase 5 comprising an upper mold chase 5a with an upper cavity and a lower mold chase 5b with a lower cavity. The upper mold chase 5a and the lower mold chase 5b for use in this disclosure are depicted in Figure 2 in a simplified way. During an injection and closure of both parts of the mold chase 5, the cavities of these parts together enclose the lead frame structure 1.

[0055] In a fifth step e) of the method according to the disclosure an encapsulating step using the moulding form occurs. During the encapsulation step the lead frame structure 1 , the at least one semiconductor die 8, the at least one connecting element 9 and in particular the plurality of lead frame junctions 6 are covered with the mold compound 10 to form the semiconductor device. Particularly, the at least one lead frame die pad 3a, 3b, the at least one lead frame terminal 4a, 4b and the plurality of lead frame junctions 6 are encapsulated. The encapsulation is such that at least parts of the at least one lead terminal 4a, 4b, being the uncovered lead frame terminals 7 are exposed and extend beyond an edge of the mold compound 10, thereby forming an encapsulated semiconductor device. The applied mold compound 10 holds the parts of the lead frame structure 1 in aligned and adjusted positions at later stages of the manufacturing method.

[0056] Custom moulding forms define a shape of the mold compound 10. The encapsulation plays a crucial role in shielding the semiconductor die 8 and its connecting elements 9 from environmental factors such as dust, dirt, mechanical damage, or moisture. The mold compound 10 can be made of plastic, metal, ceramic, or a combination of metal and ceramic. In most cases, the mold compound 10 is plastic or epoxy resin. In a sixth step f) of the method, simultaneously with the encapsulation step, the plurality of lead frame junctions 6 in the lead frame structure 1 between the at least one lead frame die pad 3a, 3b and the at least one lead frame terminal 4a, 4b are interrupted. The interruption occurs by a pressing movement of the breaking means 11 locally through the mold compound 10 and through the plurality of lead frame junctions 6.

[0057] Figure 2 depicts the step of interruption and encapsulation. The breaking means 11 presses on the lead frame junctions 6, causing them to break - interrupt. When the lead frame junctions 6 are removed, empty gaps are left behind, resulting in disconnected parts within the lead frame structure 1. Or more precisely resulting in the at least one lead frame die pad 3a, 3b and / or the at least one lead frame terminal 4a, 4b being disconnected. Along with the gaps, openings could also be formed in the mold compound 10 as a result of the breaking means’ 11 linear motion.

[0058] This disclosure provides the step of interruption during the step of encapsulating. One example involves interrupting the lead frame junctions 6 in the mold chase 5 just before the injection of the mold compound 10 into the mold chase 5 begins. The breaking means 11 moves out to press, interrupt and then move back to the mold chase 5. Following this, the injection of the mold 10 compound starts or the injection starts during moving back of the breaking means 11 to the mold chase 5. This example creates gaps in the lead frame 1 which are filled. The second example involves interrupting the lead frame junctions 6 during or before the injection of the mold compound 10. The breaking means 11 moves out to press and interrupt during or before the injection. Then the breaking means 11 moves back after or before solidification of mold compound 10. This example creates gaps in the lead frame structure 1 that are not filled. The third example involves interruption in the mold chase 5 during or before the injection of the mold compound 10 where the breaking means 11 moves back during the injection. This example creates gaps and openings in the mold compound 10 that are filled.

[0059] In the next preferred step of connecting with a heat sink and a cooling liquid, if such gaps are not filled, an isolation layer is used with a standard cooling liquid, such as water. In other examples, a dielectric liquid is used for cooling.

[0060] As shown in Figure 2, the upper mold chase 5a with the upper cavity and the lower mold chase 5b with the lower cavity enclose the lead frame structure 1 along with the semiconductor dies 8 and connecting elements 9. The moulding compound

[0061] 10 is introduced into the mold chase 5, encapsulating the parts of the semiconductor device and the interruption of the lead frame junctions 6 occurs.

[0062] Figure 3 depicts the semiconductor device after being removed from the moulding form. The result after removing the semiconductor device from the moulding form is the semiconductor device encapsulated with the mold compound 10 without the lead frame junctions 6 within the lead frame structure 1 covered by the mold compound 10.

[0063] Figures 2 and 4 depict the breaking means 11. In one example of the disclosure, the breaking means 11 are retractive moulding pins suitable for pressing and interrupting through the plurality of lead frame junctions.

[0064] In this embodiment of the disclosure, in the sixth f) step, simultaneously with the fifth step e), the breaking means 11 move out from the moulding form, press the plurality of lead frame junctions 6 locally to interrupt through the lead frame junctions 6 between the at least one lead frame die pad 3a, 3b and / or the at least one lead frame terminal 4a, 4b. After the interruption, they return to the moulding form. Preferably, the breaking means 11 move out from the moulding form, press the plurality of lead frame junctions 6 locally through the mold compound 10 to interrupt through the lead frame junctions 6. Preferably the mold compound fills gaps received after interrupting the plurality of lead frame junctions. There is provided the encapsulated semiconductor device without any gaps. In other example may as well as fill the openings in the mold compound 10 created as a result of the breaking means'

[0065] 11 pressing movement. There is provided the encapsulated semiconductor device without any gaps and with an even layer of the mold compound 10 without openings. It can be stated that the breaking means 11 moves in the linear motion because it moves out from the molding form and then moves back to it.

[0066] Figure 2 depicts the breaking means 11 in a top view. In one example, such an incorporation of the breaking means 11 would leave the mold compound 10 with openings created by their linear motion to remove the lead frame junctions 6.

[0067] The breaking means 11 in one example may have an ending 11a of a certain shape such as flat or sharp. Figure 4 depicts an example where the endings 11a of the breaking means 11 has the sharp shape. This sharp shape enhances the pressing force of the breaking means 11 in order to interrupt the lead frame junctions 6. In another embodiment the breaking means 11 are rotatable to enhance the interruption force.

[0068] In one example of the disclosure, the step f) is followed by a step f1) of trimming to remove excess components, residual material from the exposed parts of the lead frame structure, such as lead frame junctions 6 and the outer frame 2 which are beyond the mold compound 10, leaving only the uncovered lead frame terminals 7 and / or other possible parts necessary for external connections. Preferably after step of trimming, there is a step of forming uncovered lead frame terminals 7 for connecting to a printed circuit board, PCB or other electrical components by bending or shaping.

[0069] In one example the step f) is followed by a step f2) of mounting a heat sink component to the second lead frame surface 1 b for transferring generated heat from the lead frame structure 1 to the heat sink.

[0070] According to the disclosure, the method described above introduces a semiconductor device which is novel due to the removal of the ceramic layer and introducing the simultaneous interruption of the lead frame junctions 6 during the encapsulation step. The stabilization of the floating lead frame die pads 3a and / or the floating lead frame terminals 4a within the lead frame 1 is provided by the plurality of lead frame junctions 6 which are removed by introducing interruption occurring during the encapsulation step.

[0071] According to the disclosure, the method uses a lead frame structure 1 comprising an outer frame 2, an at least one lead frame die pad 3a, 3b an at least one lead frame terminal 4a 4b and the plurality of lead frame junctions 6. The plurality of lead frame junctions 6 are suitable for interconnecting the at least one lead frame die pad 3a, 3b, the at least one lead frame terminal 4a, 4b and the outer frame 2 within the lead frame structure 1.

[0072] Figure 5 depicts examples where the plurality of lead frame junctions 6 are thinner than the lead frame die pads 3a, 3b and the lead frame terminals 4a, 4b. In a first example, the lead frame junctions 6 are positioned near the second lead frame surface 1 b. In a second example, the lead frame junctions 6 are positioned in equal distance between the first and second lead frame surfaces 1a, 1 b. In a third example, the lead frame junctions 6 are positioned near the first lead frame surface 1a. The breaking means 11 should be designed so that their shape can interrupt any possible example of the lead frame junctions 6. According to the disclosure, the method uses a moulding form for applying a mold compound 10 over a lead frame structure 1. Figures 2 and 4 depict the moulding form, in particular they depict a mold chase 5. The moulding form comprises the mold chase 5 comprising an upper mold chase 5a with an upper cavity and a lower mold chase 5b with a lower cavity and a gate. Further the mold chase 5 comprises a breaking means 11 driven by a movement system. The upper mold chase 5a and the lower mold chase 5b of the moulding form are suitable for enclosing the lead frame structure 1. As it was indicated above, the mold chase 5 is designed as a two-part mold chase 5. The mold chase 5 is designed each time to be suitable for each semiconductor device. The gate is suitable for transferring the mold compound 10 into the mold chase 5.

[0073] The breaking means 11 are suitable for pressing and interrupting through the plurality of lead frame junctions 6 within the lead frame structure 1 locally by a pressing movement. The movement of the breaking means 11 is driven by the movement system. In one example, the movement system is part of a general moulding pin movement system of the moulding form, which also comprises a movement of pins 12. Figures 2 and 4 depict the mold chase 5 in a simplified way.

[0074] The breaking means 11 in the moulding form are designed to correspond to the positions of the lead frame junctions 6. The breaking means 11 and the lead frame junctions 6 are designed together to match their positions to facilitate an interruption. The design should comprise determining a distance, quantity and length of the breaking means 11 in accordance with the thickness and location of the lead frame junctions 6.

[0075] The upper mold chase 5a with the upper cavity and the lower mold chase 5b with the lower cavity of the moulding form enclose the lead frame structure 1 with an at least one semiconductor die 8, an at least one connecting element 9 and an at least one lead frame terminal 4a, 4b. Uncovered lead frame terminals 7 and / or any other possible part suitable for external connection extend outward beyond an edge of the cavities. The upper and lower cavities are filled with the mold compound 10 when the semiconductor device components are enclosed. Typically, the mold compound 10 is heated and then compressed into the gate that direct it into the cavities.

[0076] In one example, the breaking means 11 are retractive moulding pins suitable for pressing and interrupting through the lead frame junctions 6. The retractive moulding pins are standard moulding parts used in typical moulding processes. This example utilizes the existing retractive moulding pins in the moulding form. In another embodiment the breaking means 11 are rotatable to enhance the interruption force.

[0077] Figures 2 and 4 depict an example of the mold chase 5 comprising the breaking means 11 in a way suitable for moving out from the moulding form through the mold chase 5, pressing the lead frame junctions 6, interrupting through the lead frame junctions 6 and moving back to the mold chase 5. The movement of the breaking means 11 may be called a linear movement. In one example, the breaking means 11 move out and move back to the upper mold chase 5a. In other example, the breaking means 11 move out and move back to the lower mold chase 5b. The solution also discloses the example of localization in both parts of the mold chase 5.

[0078] Figures 2 and 4 depicts an example of the breaking means 11 comprising an ending 11a for being in contact with the lead frame junctions 6. Preferably, the ending 11a is flat or sharp. Figure 4 depicts an example where the endings 11a of the breaking means 11 have the sharp shape. Figure 2 depicts an example where the endings 11a have the flat shape. This sharp shape enhances the pressing force of the breaking means 11 in order to interrupt the lead frame junctions 6.

[0079] Figures 2 and 4 depict an example where the upper and / or lower cavity in one example may be flat or may have protruded structures 5c which are arranged for interacting with the breaking means 11 as it depicted in Figure 4. The interaction occurs when, during the interruption of the lead frame junctions 6, the ending 11a of the breaking means 11 is in contact with the protruded structures 5c. The interaction is the same in the case of the flat cavity - during the interruption of the lead frame junctions 6, the ending 11a of the breaking means 11 is in contact with the flat cavity.

[0080] In the case where the upper mold chase 5a comprises the breaking means 11 , the lower cavity is flat or may have protruded structures 5c. In another example, where the lower mold chase 5b comprises the breaking means 11 , the upper cavity is flat or may have protruded structures 5c. The solution also discloses an example of the upper cavity and the lower cavity being flat or having protruded structures 5c.

[0081] When designing the moulding chase 5 and its cavities, it is important to consider the arrangement of the plurality of lead frame junctions 6, the breaking means 11 , and the protruded structures 5c so that, during the placing of the lead frame structure 1 with the at least one semiconductor die 8 and the at least one connecting element 9 into the mold chase 5, all these elements interact with high precision. Figure 4 depicts an example where each protruded structure 5c is positioned opposite the corresponding breaking means 11 . Such protruded structures 5c enhance the pressing force of the breaking means 11 providing interruption from both sides of the lead frame junctions 6.

[0082] The mold chase 5 and the breaking means 11 may be made of steel or metal alloys used typically in moulding forms such as stainless steel, H13 tool steel, high speed steel, high-strength steel, wear-resistant steel, beryllium copper alloy or tungsten carbide. The breaking means 11 are preferably coated with a layer that enhances strength and anti-wear properties. The coating may be a ceramic or metal.

[0083] Figure 2 depicts an example of the disclosure where the moulding form comprises an at least one pin 12 mounted in the mold chase 5 suitable for pressing the lead frame structure 1. Preferably, the pins 12 press the at least one lead frame die pad 3a, 3b and / or the at least one lead frame terminal 4a, 4b to ensure the tight contact between the lead frame structure 1 and the opposite mold chase 5 during the encapsulating step. This tight contact prevents molding issues from occurring. Lack of tight contact between the placed components in the mold chase 5 and the mold chase 5may result in an uneven positioning of the components in the mold chase 5 and therefore an uneven distribution of the mold compound 10. Additionally, it prevents the leakage of mold compound beneath the lead frame structure 1 , which could cause overholding issues. In one example the upper mold chase 5a or the lower mold chase 5b comprises the pins 12. I one example, they are located in the same mold chase 5 as the breaking means 11. The solution also discloses an example of localization in both parts of the mold chase 5. In one example the pins 12 are retractive moulding pins.

[0084] Preferably, during the step f) of interrupting, the pins 12 move out of and back into the mold chase 5 at the same time as the breaking means 11. The movement of the pins 12 may be called a linear movement. During the design of the moulding form and its components, the pins 12 are designed in such a way that they move out from the mold chase 5 and only press the lead frame structure 1 , without causing it to break / interrupt or any other damage. In one example, such an incorporation of the pins 12 leave the mold compound 10 with openings created by their linear motion as it is depicted in Figure 2. In one example, the incoming mold compound 10 in the step of interruption fills the openings in the mold compound 10.

[0085] LIST OF REFERENCE NUMERALS USED

[0086] 1 lead frame

[0087] 1a first lead frame surface

[0088] 1 b second lead frame surface

[0089] 2 outer frame

[0090] 3a separated lead frame die pad

[0091] 3b lead frame die pad

[0092] 4a separated lead frame terminal

[0093] 4b lead frame terminal

[0094] 5 mold chase

[0095] 5a upper mold chase

[0096] 5b lower mold chase

[0097] 5c protruding structure

[0098] 6 lead frame junction

[0099] 7 uncovered lead frame terminal

[0100] 8 semiconductor die

[0101] 9 connecting element

[0102] 10 mold compound

[0103] 11 breaking means

[0104] 11a ending of breaking means

[0105] 12 pin

Claims

CLAIMS1. A method for manufacturing a semiconductor device, the method comprising: a) providing a lead frame structure with a first lead frame surface and an opposite second lead frame surface, where the lead frame structure comprises: an outer frame, an at least one lead frame die pad, an at least one lead frame terminal, and the plurality of lead frame junctions which are suitable for locally interconnecting the at least one lead frame die pads, the at least one lead frame terminal and the outer frame, b) mounting an at least one semiconductor die on the at least one lead frame die pad, c) mounting an at least one connecting element for creating electrical connection between the at least one semiconductor die and the at least one lead frame terminal, d) placing the lead frame structure, the at least one semiconductor die and the at least one connecting element in a molding form, wherein the molding form comprises a breaking means for pressing and interrupting through the plurality of lead frame junctions, e) encapsulating by a mold compound, using the molding form, the lead frame structure with the at least one semiconductor die and the at least one connecting element, such that at least part of the at least one lead terminal is exposed and thereby forming an encapsulated semiconductor device, f) interrupting, simultaneously with the encapsulation step in the molding form, the plurality of lead frame junctions in the lead frame structure between the at least one lead frame die pad and the at least one lead frame terminal by a pressing movement of the breaking means of the molding form locally through the plurality of lead frame junctions.

2. The method for manufacturing the semiconductor device according to claim 1 , wherein step f) of interrupting the plurality of lead frame junctions is by a pressing movement of the breaking means of the molding form locally through the mold compound and through the plurality of lead frame junctions.

3. The method for manufacturing the semiconductor device according to claim 1 or 2, wherein the breaking means in the step f) move out from the molding form, press the plurality of lead frame junctions to interrupt interconnection between the at least one lead frame die pad and the at least one lead frame terminal, interrupt through theplurality of lead frame junctions, move back to the molding form, preferably the mold compound fills gaps received after interrupting the plurality of lead frame junctions.

4. The method for manufacturing the semiconductor device according to claim 1 , 2 or 3 wherein the breaking means are retractive molding pins suitable for pressing and interrupting the plurality of lead frame junctions.

5. The method for manufacturing the semiconductor device according to any of the preceding claims, wherein the breaking means comprises an ending suitable for being in contact with the plurality of lead frame junctions, preferably the ending is flat or sharp.

6. The method for manufacturing the semiconductor device according to any of the preceding claims, wherein the breaking means are rotatable.

7. The method for manufacturing the semiconductor device according to any of the preceding claims, wherein step f) is followed by a step f1) of trimming, using a trimming tool, residual material from the exposed parts of the lead frame structure.

8. The method for manufacturing the semiconductor device according to any of the preceding claims, wherein step f) is followed by a step f2) of mounting a heat sink component to the second lead frame surface.

9. A semiconductor device as manufactured in accordance with anyone or more of the method claims 1-8.

10. A lead frame structure for use in a method according to claim 1-8 comprising an outer frame, an at least one lead frame die pad, an at least one lead frame terminal, and a plurality of lead frame junctions which are suitable for locally interconnecting the at least one lead frame die pad, the at least one lead frame terminal and the outer frame.

11. The lead frame structure according to claim 10, wherein the plurality of lead frame junctions are thinner than the lead frame die pads and the lead frame terminals.

12. A molding form for applying a mold compound over a lead frame structure for use in a method according to claim 1-8, comprising a mold chase comprising an upper mold chase with an upper cavity and a lower mold chase with a lower cavity suitable for enclosing the lead frame structure, a gate suitable for transferring the mold compound into the mold chase, and further the mold chase comprises a breaking means suitable for pressing and interrupting through the plurality of lead frame junctions within the lead frame structurelocally by a pressing movement, wherein the pressing movement is driven by a movement system mounted in the molding form.

13. The molding form according to claim 12, wherein the breaking means are retractive molding pins suitable for pressing and interrupting lead frame junctions.

14. The molding form according to claim 12 or 13, wherein the mold chase comprises the breaking means in a way suitable for moving out from the mold chase, pressing the plurality of lead frame junctions, interrupting through the plurality of lead frame junctions and moving back to the mold chase, preferably the upper mold chase and / or the lower mold chase comprises the breaking means.

15. The molding form according to claim 12, 13 or 14, wherein the breaking means comprises an ending suitable for being in contact with the plurality of lead frame junctions, preferably the ending is flat or sharp.

16. The molding form according to any of the claims 12-15, wherein the breaking means are rotatable.

17. The molding form according to any of the claims 12-16, wherein the lower cavity and / or upper cavity is flat and / or comprises protruding structures arranged for interacting with the breaking means.

18. The molding form according to any of the claims 12-17, wherein the mold chase comprises an at least one pin suitable for pressing the lead frame structure, preferably the at least one lead frame die pad and / or the at least one lead frame terminal, preferably the upper mold chase and / or the lower mold chase comprises the at least one pin.

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