EP2954539B1 - Production method for leadframe with a spring element as a switch fuse assembly - Google Patents

Description

The invention relates to a method for producing a leadframe.

It is known from the prior art that overstressing of electrical components may cause the electrical components to operate outside the rated operating range. Exemplary is on the EP 2 511 815 A1 directed.

For example, A reduced component insulation strength of a damaged electrical component leads to an increased power conversion, which in turn can cause an inadmissible heating. Such heating can lead to considerable risks to the immediate environment, in particular to the formation of flue gases or to a fire hazard.

To avoid different arrangements are used, either a separation, such as in FIGS. 7b and 7c shown, or a targeted short circuit, as in Figure 7a shown to protect the thermally sensitive electrical component. The triggering of the respective property takes place thermally, for example by a softenable solder.

From the field of gas-filled surge arresters, eg from the DE 10 2010 015 814 A1 It is known that short circuit bars are used for transfer to a safe state. The operating principle is based on placing a soldering pills or a plastic foil under the spring-biased bracket. The inadmissible heating of the surge arrester leads to melting the underlayed materials, so that the bracket can contact the electrodes of the structure.

Furthermore, thermal separation devices for damaged overvoltage protection components, eg from the DE 42 41 311 A1 , known in which the component to be monitored via a contact element, ie indirectly, thermosensitive is connected. The thermosensitive connection is generally via a solder joint. The contact element is mounted biased or on the contact element acts a force of a second biased element, such as a spring. Exceeds the spring force, the holding force of the thermosensitive pad, eg solder joint, opens the contact and the monitored component is turned off.

Previous arrangements were characterized by the fact that they represented a high production cost and in particular required a specifically produced carrier board.

From the WO 2007/082 617 A1 is a leadframe with various contact elements known.

These arrangements were therefore comparatively expensive in the design as well as in the production, since they each required their own production.

The invention is based on the object to provide a cost-effective method with which different arrangements can be made, which allow a safe thermal shutdown especially in a small space.

The object is achieved according to the invention by a method having the features of claim 1 for producing a leadframe for an electrical component, wherein the leadframe has an integrated thermal switching device. The method comprises a step of forming a spring member from parts of a pre-punched sheet, a step of forming a holding member from parts of the pre-punched sheet, a step of forming clamping contacts from parts of the pre-punched sheet, a step of folding at least another part of the pre-punched sheet in that parts of the prepunched sheet are stacked, and a step of connecting the stacked parts by means of a thermally softenable means, wherein an electrical connection of the stacked parts is made, on.

This makes it possible that with a cost-effective method different variants are produced, which ensure safe irreversible switching in each case with small space requirements.

In an embodiment of the invention, the method further comprises the step of inserting an electrical component.

In this way, a cost-effective overall production can be made possible.

According to a further embodiment of the invention, the method further comprises the step of separating parts of the pre-cut sheet metal.

As a result of the manufacture obsolete parts are separated, which are for further use, e.g. a re-production of a sheet can be used.

According to yet another embodiment of the invention, the pre-punching of the sheet is also provided.

This makes it possible to achieve a more cost-effective integration of manufacturing.

According to yet another embodiment of the invention, the step of connecting the superimposed parts by means of a thermally softenable agent, soldering or gluing on.

According to yet another embodiment of the invention, the method further comprises the step of folding a further part of the sheet, so that this further part is arranged over the connected superimposed parts of the sheet and spaced therefrom.

As a result, a second embodiment variant can be produced inexpensively without requiring a completely new design.

The invention will be explained in more detail with reference to the accompanying drawings with reference to preferred embodiments.

Fig. 1

eine Rohform eines Leadframes in Aufsicht gemäß einer ersten bevorzugten Ausführungsform der Erfindung,

Fig. 2a und 2b

einen Leadframe gemäß einer ersten bevorzugten Ausführungsform der Erfindung nach einem Arbeitsschritt gemäß der Erfindung in Aufsicht und seitlicher Ansicht,

Fig. 3a und 3b

einen Leadframe gemäß einer ersten bevorzugten Ausführungsform der Erfindung nach einem anderen Arbeitsschritt gemäß der Erfindung in Aufsicht und seitlicher Ansicht,

Fig. 4a und 4b

einen Leadframe gemäß einer ersten bevorzugten Ausführungsform der Erfindung nach einem weiteren Arbeitsschritt gemäß der Erfindung in Aufsicht und seitlicher Ansicht,

Fig. 5

eine Rohform eines Leadframes in Aufsicht gemäß einer zweiten bevorzugten Ausführungsform der Erfindung,

Fig. 6

einen Leadframe gemäß einer zweiten bevorzugten Ausführungsform der Erfindung als Ergebnis von Arbeitsschritten gemäß der Erfindung in Aufsicht,

Fig. 7a, 7b und 7c

unterschiedliche Anordnungen von thermischen Schaltelementen zum Schutz von elektrischen Bauelementen.

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Fig. 1

a raw form of a leadframe in plan view according to a first preferred embodiment of the invention,

Fig. 2a and 2b

a leadframe according to a first preferred embodiment of the invention after a step according to the invention in plan view and side view,

Fig. 3a and 3b

a leadframe according to a first preferred embodiment of the invention after another step according to the invention in plan view and side view,

Fig. 4a and 4b

a leadframe according to a first preferred embodiment of the invention after a further step according to the invention in plan view and side view,

Fig. 5

a raw form of a leadframe in plan view according to a second preferred embodiment of the invention,

Fig. 6

a leadframe according to a second preferred embodiment of the invention as a result of operations according to the invention in supervision,

Fig. 7a, 7b and 7c

different arrangements of thermal switching elements for the protection of electrical components.

In FIG. 1 a raw form of a leadframe 1 is shown in plan view according to a first preferred embodiment of the invention as a sheet B. This differs from a second preferred embodiment of the invention, which in FIG. 5 is shown, only by the fact that here another metal strip KB is present. This sheet metal strip KB may already be missing from the raw form or else be separated off in one of the steps of the method.

In the following, therefore, the method will be illustrated with reference to the first embodiment, wherein the execution steps in this embodiment, in contrast to the second embodiment are only indicated in the text.

The raw form of the leadframe 1 has a substantially planar structure and has pre-punched areas, which are subsequently processed by forming.

For example, in a first processing step, a spring element FE can be formed. This is for example in Figure 1 and Figure 2a and 2b shown. In this case, the metal strip FE is made FIG. 1 formed by forming in a bracket, as in FIG. 2b shown in side view. For better distinction of the part of the sheet, which forms the holding element HE, marked with a hatching from bottom left to top right. The forms in FIG. 1 right widening of the sheet metal part of a nose. During the deformation, for example, the sheet metal part FE is brought by bending in a U-shape.

Likewise, a holding element HE is formed. This is reshaped so that a receptacle is formed, so that the spring element FE can be held here later. For example, on the metal strip in FIG. 1 Protrusions designed in the direction of the spring element, which now holds after deformation at a latching of the spring element FE this now releasably. When forming, for example, the sheet metal part HE is brought by bending in a U-shape.

In a further stage of the method, the spring element FE can now be activated by introducing the nose formed on the spring element FE into the holding element HE.

This can be done during the further processing steps, as in FIGS. 4a and 4b shown, or only during the actual installation of a populated leadframe in a corresponding electrical system.

Furthermore, in a separate or parallel processing step, one or more terminal contacts KK can also be formed from parts of the pre-cut sheet B. For better distinction, the part of the sheet which forms a clamping contact KK is marked with hatching from bottom right to top left. For this purpose, for example, the in FIG. 1 shown part bent upwards as in FIG. 2b seen.

In another processing step according to the invention is now, as in the side view in FIG. 3b and supervision in FIG. 3a shown, at least another part HS _{1 of} the pre-punched sheet B folded, so that parts HE, KK of the pre-punched sheet B are arranged one above the other. Other parts of the sheet are folded as needed. As a result of this deformation, the holding element HE, as can be seen in lateral view 3b, is now brought over the sheet metal element adjoining the contact element KK. The now superimposed parts HS1 and HE, KK of the pre-punched sheet B can now be connected to each other by a suitable method. The connection point should be able to be triggered thermally so that a thermally softenable agent L, for example a suitable adhesive or a suitable solder, can be used as connecting means. For better distinction, the thermally softenable agent L is exemplified as a black filled ellipse. Through the connection, an electrical connection of the superimposed parts is made.

This prefabricated leadframe 1 can now be equipped with a suitable component in a further processing step. Exemplary electrical components are thermally sensitive components, in particular (metal oxide) varistors or suppressor diodes or spark gaps or gas-filled surge arresters or resistors. The equipment can e.g. have a pressing in molded as cutting contacts contact elements KK. Of course, other joining techniques, especially soldering techniques, are equally usable.

In a further processing step according to the invention is now, as in a side view in FIG. 4b and supervision in FIG. 4a shown, at least part of the pre-cut sheet B separated. For example, the retaining strip HS _{1 is} off Figure 1 to 3b in FIGS. 4a and 4b removed, since this is no longer needed by the connection made of retaining element HE and contact strip KK. Next example, the holding strip HS _{2 is} off Figure 1 to 3b in FIGS. 3a and 3b removed, since now the contact elements KK are connected via the assembled electrical component EB. In particular, it can be provided that only one raw mold for different shapes of the leadframe according to FIG. 1 and FIG. 5 are provided, so that the raw form of the leadframes FIG. 5 can be created by separating the sheet metal part KB. This allows a cost-effective large-scale production of a single raw form, which can then be easily converted into another embodiment. The exact arrangement of the individual steps is adaptable to the respective process conditions, so that no additional processing step is necessary, but can be inserted into an existing step, whereby the processing time is not adversely affected.

In particular, a fully integrated process approach can be followed, which also includes the corresponding preparation of the raw forms of the sheet B according to the exemplary FIGS. 1 and 5 by punching from a sheet provides.

The in the Figures 1 to 4b The embodiment shown differs from the embodiment of FIG FIGS. 5 and 6 in that a further sheet metal strip KB is provided. While in the FIGS. 5 and 6 an arrangement is shown, which acts as a normally closed in a thermal softening of the connection L and thus interrupts a current flow through the electrical component EB, is in the embodiment of the Figures 1 to 4b provided that a short circuit is generated.

For this purpose, as in FIGS. 4a and 4b shown in a further or integrated processing step, a further part of the sheet B B so folded, so that this further part KB over the connected superimposed parts of the sheet B, in particular HE and KK, is arranged spaced. With a thermal softening of the connection L, the spring element FE now acts as a closer with respect to the strip KB arranged thereover, so that a current flow is conducted past the electrical component EB.

Thus, different circuits with respect to thermally sensitive electrical components can be realized with the invention in a simple, cost-effective manner. In particular, the fact that the leadframe also acts as a direct thermal connection to the thermally softenable means L fast switching times and a secure connection to the electrical component EB can be ensured. Because the thermal activatable Switching element is part of the leadframe, the necessary space is minimized. LIST OF REFERENCE NUMBERS leadframe 1 Electrical component EB switching device S spring element FE sheet B retaining element HE clamping contact KK Parts of a pre-cut sheet HS ₁ , HS ₂ thermally softenable agent L

Claims (6)

1. Method for producing a leadframe (1) for an electrical component (EB), wherein the leadframe (1) has an integrated thermal switching device (S), having the steps
   forming a spring element (FE) from parts of a pre-punched metal sheet (B),
   forming a retaining element (HE) from parts of the pre- punched metal sheet (B),
   forming terminal contacts (KK) from parts of the pre-punched metal sheet (B),
   folding at least one further part (HS₁) of the pre-punched metal sheet, so that parts (HE, KK) of the pre-punched metal sheet (B) are arranged above one another,
   connecting the parts that are arranged above one another by means of a thermally softenable means (L), wherein an electrical connection of the parts arranged above one another is produced.
2. Method according to Claim 1, also having the step of inserting an electrical component (EB).
3. Method according to Claim 1 or 2, also having the step of separating parts (HS₁, HS₂) of the pre-punched metal sheet (B).
4. Method according to any one of the preceding claims, also having the step of punching the metal sheet (B).
5. Method according to any one of the preceding claims, wherein the step of connecting the parts arranged above one another by means of a thermally softenable means (L) comprises soldering or gluing.
6. Method according to any one of the preceding claims, also having the step of folding a further part (KB) of the metal sheet (B), so that this further part is arranged above and spaced apart from the connected parts of the metal sheet (B) arranged above one another.

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