Method for potting an electronic component

Abstract

The invention relates to a method for potting an electronic component on a printed circuit board (1). In the method, a potting container (6) and a potting compound (8) are introduced to the printed circuit board (1) as part of a fitting process, wherein, after being introduced, the potting container (6) rests on the printed circuit board (1), the potting compound (8) is located in and / or on the potting container (6), and the potting container (6) surrounds the electronic component. The method according to the invention also includes fixing the potting container (6) on the printed circuit board (1). The potting compound (8) is also liquefied such that the potting compound (8) encloses the electronic component.

Description

[0001] Process for encapsulating an electronic component

[0002] The invention relates to a method for encapsulating an electronic component on a printed circuit board.

[0003] For use in harsh environments or in potentially explosive atmospheres, components of electronic devices require special protection. This can be achieved by encapsulating electronic components from the environment. For example, the electronic components can be potted. A printed circuit board with electronic components can be manufactured and protected as follows. First, the printed circuit board is populated with the electronic components, for example, SMD components. The electronic components are then fixed to the circuit board by soldering. This creates an assembly that is subsequently installed in a housing. The assembly is potted in the housing by filling the housing with a potting material. The housing is then hermetically sealed.If necessary, the housing and the encapsulated assembly must also be placed in a temperature cabinet so that the encapsulation material can harden. This process encapsulates the circuit board and all electronic components, thus protecting it from external influences.

[0004] If not all electronic components are to be encapsulated on the circuit board, a potting container can be used, sometimes also called a potting cup. A so-called board-level shield, for example, can be used as a potting container. This is a container or frame element that is particularly intended for the electromagnetic shielding of components, but is also suitable for potting purposes. The circuit board is first populated with electronic components. A potting container is placed on the circuit board so that it surrounds one or more components to be encapsulated. The potting container is then fixed to the circuit board. In a next step, the electronic components are potted in the potting container. For this purpose, the potting container is filled with a potting material.A corresponding method for encapsulating electronic components on a printed circuit board is known from the document DE 10 2010 038 294 A1. The invention is based on the object of providing a simplified method for encapsulating an electronic component on a printed circuit board. This object is achieved by the method according to claim 1. The dependent patent claims relate to optional embodiments of the invention. It is pointed out that the features listed in the patent claims can be combined with one another in any desired manner, provided this is technically expedient. This also applies if a patent claim is not dependent on another patent claim. The description characterizes and further specifies the invention, particularly in connection with the figures. The features in the description can also be freely combined with one another, provided this is technically expedient.

[0005] The invention particularly relates to a method for encapsulating an electronic component on a printed circuit board, comprising the steps of: transporting a potting container and a potting compound to the printed circuit board during an assembly process, such that after transport, the potting container rests on the printed circuit board, the potting compound is arranged in and / or on the potting container, and the potting container surrounds the electronic component. Within the scope of the method according to the invention, the potting container is also fixed to the printed circuit board. Furthermore, the potting compound is liquefied so that the potting compound encloses the electronic component. Consequently, the potting container and the potting compound are transported onto the printed circuit board during the assembly process. Thus, both the potting container and the potting compound are placed on the printed circuit board in a single operation, which simplifies the manufacturing process.Since the potting compound is also transferred to the circuit board during assembly, there is no need to subsequently place or inject the potting compound into the potting container in a separate step. The potting compound is preferably in a solid state when it is transferred to the circuit board.

[0006] The assembly process can, in particular, be a mechanical assembly process. The assembly process is preferably an SMD assembly process. This is preferably carried out by one or more automatic assembly machines. The potting compound is preferably arranged in and / or on the potting container. The potting container is advantageously dimensioned such that it is suitable for receiving and / or enclosing one or more electronic components. The potting container thus surrounds the electronic component. According to one embodiment of the invention, this can be understood as meaning that the electronic component is now arranged in a cavity formed by the potting container.

[0007] The potting container preferably forms a circumferential wall from which the potting compound cannot leak in a liquefied state. For the purposes of the present invention, an electronic component is understood to mean any electronic component, be it a resistor, a capacitor, an inductor, an integrated circuit, or any other electronic component. It is understood that multiple electronic components can also be potted using the method according to the invention.

[0008] The assembly process preferably comprises not only the placement of the potting compound or potting container onto the circuit board, but also the placement of the electronic component onto the circuit board. The electronic component is preferably placed on the circuit board before the potting container and potting compound are placed onto the circuit board. The electronic component is preferably positioned such that it electrically contacts one or more contact surfaces on the circuit board. It is understood that additional electronic components can also be placed onto the circuit board during the assembly process. These can, in particular, be electronic components that are not to be potted. After the potting container has been placed onto the circuit board, these components are located outside the potting container.

[0009] The purpose of fixing the potting container to the circuit board is to firmly connect the potting container to the circuit board. In principle, various methods are conceivable for fixing the potting container, such as soldering, gluing, or the like. To prevent the potting compound from escaping during liquefaction, the potting container is preferably sealed to the circuit board by its underside. The liquefaction of the potting compound already arranged in and / or on the potting container ensures that it encloses the electronic component. According to a variant of the invention, the potting compound can be arranged above the potting container so that it flows into the potting container as a result of the liquefaction. According to one embodiment of the invention, the potting compound is arranged such that during the liquefaction process, no or only a small amount of potting compound reaches areas of the circuit board that are outside the potting container.

[0010] Preferably, the potting compound is arranged before being placed in and / or on the potting container such that the potting compound and the potting container form a composite, wherein the composite is mechanically picked up from a storage position and placed on the circuit board for the purpose of placement. According to one variant of the invention, the potting compound is arranged in the composite on the potting container. According to another variant of the invention, the potting compound is arranged within the potting container. Furthermore, it is possible for the potting compound to be arranged both in and on the potting container. The potting container and the potting compound can be picked up together, for example by a robot arm, and transported to the circuit board. According to one variant of the invention, the composite can be removed from a placement belt by an automatic pick and place machine, wherein the placement belt provides the storage position for the composite.Thus, the potting container and the potting compound can be moved to the circuit board in a single movement. According to the invention, the potting compound can be attached to the potting container. However, it is also possible for the potting compound to form a loose connection with the potting container, for example, by resting loosely on it.

[0011] Alternatively, it can be provided that the potting container is mechanically picked up from a first storage position and placed on the circuit board, and the potting compound is mechanically picked up from a second storage position and arranged in and / or on the potting container. This can take place within two movement steps, so that, for example, the potting container is picked up from the first storage position and placed on the circuit board, and then the potting compound is picked up from the second storage position and arranged in and / or on the potting container. Alternatively, however, this can also take place in a single movement step, in which, for example, a robot arm first picks up both the potting compound and the potting container in one movement sequence and then places the potting container on the circuit board or arranges the potting compound in and / or on the potting container.

[0012] The previously described steps for moving the potting compound and the potting container, with the potting container initially located at the first storage position and the potting compound initially located at the second storage position, can in particular be carried out by the same machine, for example, by the same placement machine. However, it is also possible according to the invention for these steps to be carried out by different machines, for example, different placement machines. According to one variant of the invention, the first storage position and the second storage position are provided by a placement belt or belts of a placement machine.

[0013] The encapsulation container preferably forms a cavity, wherein the encapsulation container has at least one lower opening and at least one upper opening, and wherein the encapsulation container is placed on the circuit board such that the at least one lower opening faces the circuit board. When the encapsulation container is arranged on the circuit board, the cavity of the encapsulation container preferably surrounds the electronic component or several electronic components to be encapsulated. The at least one upper opening is preferably arranged on the encapsulation container opposite the at least one lower opening.

[0014] It is advantageous if the encapsulation container has a lower edge, wherein at least the lower edge of the encapsulation container is formed by a metal suitable for soldering, and wherein the encapsulation container is placed on the circuit board such that the lower edge of the encapsulation container contacts a solder paste arranged on the circuit board. It is possible for the encapsulation container to be formed entirely by the metal suitable for soldering. Preferably, the solder paste is placed on the circuit board in advance. The solder paste is preferably arranged circumferentially around the electronic component such that the lower edge of the encapsulation container contacts the solder paste circumferentially and without interruption. The circuit board preferably has a suitably dimensioned metallic surface area on which the solder paste is placed.By soldering the circuit board to the potting container using the solder paste, a sealing connection is preferably created between the potting container and the circuit board, so that the potting compound in its liquefied state cannot escape from the underside of the potting container and reach areas of the circuit board that are located outside the potting container.

[0015] The potting container does not necessarily have to be soldered to the circuit board. Other methods for securing the potting container to the circuit board are also conceivable. For example, the potting container can be glued to the circuit board.

[0016] According to a particular embodiment of the invention, the potting container and the potting compound are complementarily shaped, at least in sections, wherein the potting container is positively connected to the potting compound after placement and optionally also before placement. For example, the potting compound can have projections or elevations that can be inserted into openings in the potting container. The positive connection between the potting container and the potting compound prevents the potting compound from becoming detached from the potting container too easily, for example when a composite of the potting container and the potting compound is transported to the circuit board. It is possible according to the invention for the potting container and the potting compound to already be positively connected to one another before they are transported together to the circuit board.According to other embodiments of the invention, the potting container and the potting compound are initially separated from each other and are only positively connected to each other on the circuit board. The positive connection is preferably established by simply plugging the potting container and the potting compound together.

[0017] The potting compound is advantageously heated, injected into a mold in the heated state, and after solidification, mechanically picked up and placed onto the potting container. The potting compound is thus first formed into a suitable shape. The mold can be designed so that the potting compound takes on a shape that is at least partially complementary to a shape of the potting container. According to one possible variant of the invention, the potting compound is heated mechanically and injected into the mold. This can be done according to the invention by means of an automatic placement machine or in an automatic placement machine. According to other variants of the invention, these steps can also be performed by another machine. The potting compound is preferably picked up mechanically using a vacuum pipette and placed onto the potting container. This can be done by the aforementioned automatic placement machine.However, the casting compound does not necessarily have to be brought into a suitable form within the scope of the present process, but can also already be available in a form suitable for carrying out the process.

[0018] The potting compound is preferably formed from a hot melt. This is a thermoplastic material that is solid at room temperature and liquefies when heated. It is therefore suitable for encapsulating electronic components. The hot melt is preferably first heated and then molded into a suitable shape using a casting process. After cooling, it is applied to the circuit board as described above and placed in and / or on the potting container. The hot melt is then heated again so that it liquefies and encloses the electronic component. The hot melt then cools again, solidifying again and protectively surrounding the electronic component.

[0019] According to one possible embodiment of the method according to the invention, the at least one electronic component is glued to the circuit board before the potting container and the potting compound are placed on the circuit board. This prevents the electronic component from slipping when the potting compound is liquefied. According to one embodiment of the invention, the bonding can be carried out by the pick and place machine. According to other embodiments of the invention, it can be provided that the electronic component is soldered to the circuit board. The electronic component is preferably fixed to the circuit board before the potting container and the potting compound are placed on the circuit board. According to other variants of the invention, the electronic component is only fixed afterwards, for example during a soldering process in which the potting container is also fixed to the circuit board.It is advantageous if the encapsulation container is fixed to the circuit board and the liquefaction of the encapsulation compound takes place simultaneously. According to the invention, the encapsulation container is fixed to the circuit board by soldering and the liquefaction of the encapsulation compound can take place simultaneously, for example by a heating process. Alternatively, it is conceivable for the encapsulation container to be fixed to the circuit board and the liquefaction of the encapsulation compound to take place one after the other. Within the scope of the present invention, no mandatory sequence is specified for the encapsulation container being fixed to the circuit board and the liquefaction of the encapsulation compound. According to preferred embodiments of the invention, it is provided that the encapsulation container is first sealed to the circuit board so that the encapsulation compound cannot escape from the encapsulation container as soon as it is liquefied.

[0020] The encapsulation container is preferably secured to the circuit board and the liquefaction of the encapsulation compound is preferably achieved through a heating process. The encapsulation container can be secured to the circuit board, in particular, by soldering the encapsulation container to the circuit board. Soldering can also be used to secure other electronic components to the circuit board. These can be SIMD components with which the circuit board was previously mechanically populated. A soldering oven is preferably used for heating. The heating required for the soldering process can, according to the invention, also lead to liquefaction of the encapsulation compound.

[0021] According to advantageous variants of the invention, the liquefaction of the casting compound can be achieved by exposure to light, application of a voltage, or by combining the casting compound with a liquid. For example, the casting compound can be exposed to infrared radiation or some other type of light, causing it to liquefy. It is also conceivable to apply a voltage to the casting compound, causing it to liquefy. Finally, the casting compound can be combined with a liquid, for example, by pouring the liquid over it. This can also cause the casting compound to liquefy. In all of the cases mentioned, it is assumed that the liquefaction process is reversible, for example through cooling, evaporation of liquid components, a chemical reaction, etc. The casting compound can then solidify again.

[0022] Preferably, the assembly process is performed by an automatic placement machine. A placement machine is understood to be a machine used in the production of printed circuit boards to place components onto the circuit board, which are then soldered in a soldering process. This is preferably an automatic placement machine for SMD assembly. According to advantageous embodiments of the invention, the same placement machine carries out the transfer of both the potting container and the potting compound to the circuit board.

[0023] Advantageous embodiments of the invention are explained by way of example in the drawings. Herein:

[0024] Figure 1 is a schematic representation of a section of a printed circuit board before a placement process.

[0025] Figure 2 is a schematic representation of the section of the printed circuit board after assembly with an electronic component,

[0026] Figure 3 is an expanded schematic representation with a section of the circuit board after assembly with the electronic component,

[0027] Figure 4 is a schematic representation of a potting container,

[0028] Figure 5 is a schematic representation of the circuit board, with the potting container placed on the circuit board,

[0029] Figure 6 is a schematic representation of a potting compound in a view from above,

[0030] Figure 7 is a schematic representation of the potting compound in a view of an underside of the potting compound, Figure 8 is a schematic representation of the circuit board after the potting compound has been placed on the potting container,

[0031] Figure 9 is a schematic representation of the circuit board after liquefaction of the potting compound and

[0032] Figure 10 is a schematic representation of a composite consisting of a potting container and a potting compound.

[0033] Figure 1 shows a schematic representation of a section of a printed circuit board 1 prior to a placement process. The printed circuit board 1 has metallic contact pads 2 and conductor tracks 3. The printed circuit board 1 is intended for assembly with SMD components. Electrical components are placed on the printed circuit board 1, making electrical contact with the contact pads 2. This is performed by an automatic placement machine.

[0034] Figure 2 shows a schematic representation of a section of circuit board 1 after assembly with an electronic component 4. The assembly was performed by the assembly machine. The electronic component 4 is a resistor that electrically contacts the contact surfaces 2. To prevent the electronic component 4 from slipping during the subsequent steps, it is glued to the circuit board 1.

[0035] Figure 3 shows an expanded schematic representation of a section of the circuit board 1 after the electronic component 4 has been assembled. A solder paste 5 is arranged on the circuit board 1 surrounding the electronic component 4. This solder paste is applied to a metallic section of the circuit board 1.

[0036] Figure 4 shows a schematic representation of a potting container 6. The potting container 6 has four upper openings 7 and one lower opening. The potting container 6 is formed from a metal suitable for soldering.

[0037] Figure 5 shows a schematic representation of the printed circuit board 1, with the encapsulation container 6 placed on the printed circuit board 1. For this purpose, the placement machine has removed the encapsulation container 6 from a placement belt of the placement machine and moved it to the printed circuit board 1. The placement machine has placed the encapsulation container 6 on the printed circuit board 1 such that a lower edge of the encapsulation container 6 makes circumferential contact with the solder paste. The encapsulation container 6 surrounds the electronic component 4.

[0038] Figure 6 shows a schematic representation of a potting compound 8 in a top view. The potting compound 8 is formed by a hot melt. This is solid at room temperature. The hot melt is prepared by first heating the potting compound 8 and injecting it into a mold. The potting compound 8 then assumes the shape shown in Figure 6. After solidification, the potting compound 8 is removed from the mold and placed on a placement belt of the placement machine.

[0039] Figure 7 shows a schematic representation of the potting compound 8 in a view of a bottom side of the potting compound 8. The bottom side of the potting compound 8 is shaped complementarily to a top side of the potting container: The potting compound 8 has four raised areas 9 that match the upper openings of the potting container.

[0040] Figure 8 shows a schematic representation of the printed circuit board 1 after the potting compound 8 has been applied to the potting container 6. The potting compound 8 was removed from the assembly tape by the placement machine and placed on the potting container 6. Since the potting container 6 and the potting compound 8 are complementarily shaped in sections, they are now positively connected to one another. This prevents the potting compound 8 from slipping sideways from the potting container 6. The printed circuit board 1 is then removed from the placement machine and placed in a soldering oven. The soldering oven is switched on, and the ambient temperature of the printed circuit board 1 rises. This solders the potting container 6 to the printed circuit board 1, thus fixing the potting container 6 to the printed circuit board 1. Furthermore, the potting compound 8 liquefies as a result of the rising ambient temperature.It flows into a cavity formed by the potting container 6, in which the electronic component is also located.

[0041] Figure 9 shows a schematic representation of the printed circuit board 1 after the liquefaction of the potting compound 8. The potting compound 8 now completely fills the cavity formed by the potting container 6 and covers the electronic component. After the soldering furnace is switched off, the potting compound 8 cools down and subsequently solidifies again. The potting compound 8 now protectively encloses the electronic component. Figure 10 shows a schematic representation of a composite 10 comprising a potting container 6 and a potting compound 8. According to a different variant of the method according to the invention for potting an electronic component on a printed circuit board, the potting container 6 and the potting compound 8 are not brought separately to the printed circuit board. Instead, they are present in advance in the illustrated composite 10 and are located in a storage position of the automatic pick and place machine.The assembly machine picks up the assembly 10 and places it on the circuit board in such a way that a lower edge of the potting container 6 makes circumferential contact with a solder paste arranged on a circuit board as shown in Figure 3. Subsequently, the previously described steps for fixing the potting container 6 to the circuit board and for liquefying the potting compound 8 can be performed.

[0042] List of reference symbols

[0043] 1 circuit board

[0044] 2 Contact surface 3 Conductor track

[0045] 4 Electronic component

[0046] 5 Solder paste

[0047] 6 Potting container

[0048] 7 Upper opening 8 Potting compound

[0049] 9 Sublime Area

[0050] 10 Association

Claims

Patent claims 1. A method for encapsulating an electronic component (4) on a printed circuit board (1), comprising the steps: - bringing a potting container (6) and a potting compound (8) to the printed circuit board (1) during an assembly process, so that after bringing the potting container (6) sits on the printed circuit board (1), the potting compound (8) is arranged in and / or on the potting container (6), and the potting container (6) surrounds the electronic component (4), - fixing the potting container (6) to the circuit board (1), and - liquefaction of the potting compound (8) so that the potting compound (8) encloses the electronic component (4).

2. Method according to claim 1, characterized in that the potting compound (8) is arranged in and / or on the potting container (6) before being placed therein, so that the potting compound (8) and the potting container (6) form a composite (10), wherein for the purpose of placing the composite (10) is mechanically picked up from a storage position and placed on the printed circuit board (1).

3. Method according to claim 1, characterized in that for the transfer the potting container (6) is mechanically picked up from a first storage position and placed on the circuit board (1), and the potting compound (8) is mechanically picked up from a second storage position and arranged in and / or on the potting container (6).

4. Method according to one of the preceding claims, characterized in that the potting container (6) forms a cavity, wherein the potting container (6) has at least one lower opening and at least one upper opening (7), and wherein the potting container (6) is so arranged on the Printed circuit board (1) is placed so that the at least one lower opening faces the printed circuit board (1).

5. Method according to one of the preceding claims, characterized in that the potting container (6) has a lower edge, wherein at least the lower edge of the potting container (6) is formed by a metal suitable for soldering, and wherein the potting container (6) is placed on the circuit board (1) in such a way that the lower edge of the potting container (6) contacts a solder paste (5) arranged on the circuit board (1).

6. Method according to one of the preceding claims, characterized in that the potting container (6) and the potting compound (8) are shaped complementarily at least in sections, wherein the potting container (6) is positively connected to the potting compound (8) after the transfer and optionally before the transfer.

7. Method according to one of the preceding claims, characterized in that the casting compound (8) is heated, is injected into a casting mold in the heated state and, after solidification, is mechanically picked up and placed on the casting container (6).

8. Method according to claim 7, characterized in that the casting compound (8) is picked up mechanically with the aid of a vacuum pipette and placed on the casting container (6).

9. Method according to one of the preceding claims, characterized in that the casting compound (8) is formed by a hot melt.

10. Method according to one of the preceding claims, characterized in that the at least one electronic component (4) is glued to the circuit board (1) before the potting container (6) and the potting compound (8) are placed on the circuit board (1).

11. Method according to one of the preceding claims, characterized in that the fixing of the potting container (6) to the circuit board (1) and the liquefaction of the potting compound (8) take place simultaneously.

12. Method according to one of the preceding claims, characterized in that the fixing of the potting container (6) to the circuit board (1) and the liquefaction of the potting compound (8) are carried out by a heating process.

13. Method according to one of claims 1 to 11, characterized in that the liquefaction of the casting compound (8) takes place by exposure to light, application of a voltage or combining the casting compound (8) with a liquid.

14. Method according to one of the preceding claims, characterized in that the assembly process is carried out by an automatic assembly machine.

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