DE29907053U1 - Device for electrical contacting - Google Patents

Description

29 March 1999

ROBERT BOSCH GmbH, 70442 Stuttgart

Device for electrical contact

The invention relates to a device for the electrically conductive connection of a connection contact to a conductor track on a circuit board, wherein the circuit board has a contacting eye for receiving the connection contact and the conductor track is brought to the contacting eye on the surface or an intermediate layer of the circuit board.

The contact between conductor tracks on a circuit board and active or passive components has so far been made by soldering, plugging or bonding. Contact eyes are first created in the circuit board, for example by drilling or punching a hole that is usually circular. The connecting conductors or contact pins of the components are inserted into the contact eye and connected electrically using an additional material. In order to enable the respective component to be optimally attached to the circuit board, the conductor track is applied in a ring around the contact eye on the surface of the circuit board. In this way, the solder connects to the ends of the connecting contacts or contact pins of the components and, via the ring-shaped section of the conductor track, to the circuit board itself.

This conventional connection technique requires an additional material, such as solder, and the components heat up during the soldering process, which often leads to component failure. The components are also removed from the circuit board by heating the solder, which is usually time-consuming and therefore expensive.

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A conventional, metallic plug connection requires complex and therefore expensive male and female plugs, which require a lot of space and are complex and therefore expensive to manufacture.

The present invention is based on the object of developing a device for electrical contacting of the type described at the outset in such a way that reliable contacting of electrical components on a circuit board is possible without the use of an additional material such as solder.

This object is achieved according to the invention by the features of claim 1. According to this, a metal layer on the inner peripheral walls of the contact eye is in conductive connection with the conductor track and the inner dimensions of the contact eye are adapted to the outer dimensions of the connection contact such that the connection contact can be clamped into the contact eye.

According to the invention, it has been recognized that a secure contact of electrical conductor tracks is possible without the use of an additive, i.e. a solder. For this purpose, a deformable metal layer must be provided on the inner peripheral walls of the contact eye. The connection contact is then clamped in a force-fitting manner within the contact eye between the inner peripheral walls and is thereby simultaneously fastened to the circuit board and electrically connected to the conductor track.

This makes it particularly advantageous to make contact without additional materials, which means that contact can also be made on multilayer boards. Greater flexibility in connecting the connection contacts to the contact eyes is possible, as position tolerances can be compensated for by deforming the inner metal layer. As a result, lower tolerance requirements are necessary and the risk of damage to the electrically conductive connection during assembly is lower. Finally, an easily detachable connection is possible without the conventional desoldering of the connection.

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contacts. The temperature effect when soldering sensitive components is also eliminated.

According to the invention, the peripheral walls of the contact eye provided with the metal layer are adapted to the external dimensions of the connection contact in such a way that the connection contact can be clamped into the contact eye. For example, in the case of a contact eye with a circular cross-section and a flat connection contact, the contact eye deforms when the connection contact is inserted so that after the connection process the contact eye takes on a substantially oval shape and the peripheral walls adapt to the external dimensions of the connection contact. This creates contact forces on the narrow side of the connection contacts so that they are firmly fixed in the contact eye.

In a particularly advantageous development of the invention, at least the inner peripheral walls of the contact eye are made of a deformable plastic with a metallized surface. The metallization is on the inside of the contact eye. In the simplest case, the metallized plastic consists of a homogeneous plastic and a homogeneous metal layer applied to its surface, i.e. to the inner peripheral walls of the contact eye. The metal layer can also be partially incorporated into the surface of the plastic, for example in the form of fibers. This creates a partially metallized plastic with a specially embedded metal structure. The metal fibers could form a lattice structure within the plastic.

Preferably, the metal material is applied in the form of a layer to the surface of the plastic. This can be done in particular by electroplating. The metallized plastic now forms the inner peripheral walls of the contact eye and can be combined with a conventional circuit board. The metallized plastic can then preferably be deformed either elastically or plastically, depending on how often a component is to be removed from the contact eye. The metallized plastic has excellent deformation properties for the force-fluid attachment of the connection contacts.

and the metallization also creates electrical connections with a low contact resistance.

The metal layer or metal material is preferably tin or a tin alloy. The plastic can be a polyamide, for example. Of course, another highly conductive metal such as copper or a copper alloy can be used instead of tin. The plastic can be selected according to its deformability and suitability for producing a metallized plastic. Finally, the plastic could also be a conventional circuit board material.

In a preferred development of the invention, the thickness of the circuit board increases in the area of the contact eye. The contact eye can also protrude with its peripheral walls on the top or bottom of the circuit board. Due to the greater thickness of the circuit board in the area of the contact eye, the area of the peripheral walls is enlarged there, so that higher fastening forces act on the connection contact and the deformation of the contact eye takes place over a larger area.

The contact eye is preferably elastically deformable in its cross-section when the connection contact is inserted. The external dimensions of the connection contact are always slightly larger than the internal dimensions or the diameter of the contact eye. As a result, the softer metallized plastic or the softer metal material deforms when the connection contact made of a harder material is inserted. Due to the plastic deformation, the outer circumference of the connection contact is secured there by the deformed peripheral walls of the contact eye. The high contact force and the enlarged contact surface result in a very low contact resistance at the connection point. In particular with a flat contact pin with two narrow sides or edges, an originally circular contact eye can deform to an approximately oval shape in cross-section. Contact forces arise on the narrow sides, especially at the edges of the connection contacts.

In a particularly preferred development of the invention, the contact eye decreases in cross-section in the direction of insertion of the connection contact. As a result, the deformation force on the peripheral walls increases when inserting the connection contact with increasing penetration depth.

The contact eye preferably has an inner peripheral wall with a wall step. This also reduces the cross-section of the contact eye in the direction of insertion of the connection contact. On one side of the wall step, the peripheral walls have a larger inner diameter to accommodate the connection contact and on the other side of the wall step, the inner diameter or the inner dimensions of the contact eye are smaller. This creates two independent sections in the contact eye, each of which has a matching stepped connection contact separately contacting the peripheral walls made of metallized plastic. This ensures that at least one electrically conductive connection is made, even with larger tolerances.

In a special design, the contact eye has a cylindrical passage in the circuit board with an inner ring step. This specially designed contact eye can be created, for example, by a punching or drilling process in the circuit board. However, instead of a circular cross-section, the contact eye can also have a square or rectangular cross-section. The ring step serves as a stop on the one hand and to separate the two contact sections on the peripheral wall inside the contact eye on the other.

The connection contact is also preferably designed to be stepped in the longitudinal direction, so that it is limited in the insertion direction by the stepped contact eye. Since the connection contact is designed to be stepped, its peripheral step or edge strikes the inner wall step of the peripheral wall of the contact eye. This ensures that the connection contact is arranged in the contact eye in the intended installation position after the connection process.

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The connecting contact is advantageously larger in the dimensions of its cross section than the corresponding dimension, e.g. the diameter, of the contact eye. In particular, if two contact sections are formed by the wall step in the contact eye, the connecting contact has an end section with a smaller width and a front section with a larger width, which are each slightly larger than the smaller diameter or the larger diameter of the contact eye. The connecting contact is advantageously designed as a conductor surface and therefore has two opposite edges or narrow sides. The cross section of the connecting contact is then rectangular. The edges of the connecting contact can be rounded by rubbing or tapping. The surfaces of the peripheral walls of the contact eye and the connecting contact can each be tinned.

The connection contact has two opposing edges or narrow sides that cause the contact eye to be deformed. Due to the flat design of the connection contact, its narrow sides abut the peripheral walls of the contact eye and cause the contact eye to be deformed. If the contact eye is originally circular, it becomes approximately oval after the connection process. This creates contact forces on the narrow sides of the connection contact. When the connection contact and the contact eye are designed in a stepped design, different deformation forces can act in the two passage sections. This essentially creates two separate electrically conductive connections in both passage sections separated by the wall step. The contact eye has two passage sections with different dimensions adjacent to a wall step. In the simplest case, the passage sections are cylindrical with different diameters and a ring step arranged between them.

The two separate through sections create a contact on two opposite edges of the connection contact. This results in increased contact reliability through redundancy. Finally, if the contact force decreases, the second contact point can take over the electrically conductive connection alone.

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When the connection contact is inserted, the two through sections deform in such a way that the contact eye protrudes beyond the circuit board on the top and/or bottom. In addition to the plastic or elastic deformation of the peripheral walls perpendicular to the connection contact, the metallized plastic can also be pressed beyond the surface of the circuit board. In this way, even large tolerances of the connection contacts can be compensated. In addition, if the connection contacts, i.e. the contact pins in integrated circuits, are skewed, a corresponding contact force can be applied. The height of the contact eye is therefore greater than the thickness of the circuit board. The diameters of the through sections separated by the wall step can deform to different degrees, largely independently of one another. This creates a high degree of flexibility on the peripheral walls of the contact eye. Position tolerances are compensated. This makes it possible to achieve lower tolerance requirements and a lower risk of damage during assembly.

The contact eye preferably has insertion bevels and/or rounded edges arranged on the inside. This makes it easier to insert the connection contact and the deformation of the peripheral walls can also be controlled by the insertion bevels of the rounded edges. The connection contact also has matching rounded edges and joining bevels. When joining, a slight plastic deformation takes place on the surface of the metallized plastic, which leads to improved electrically conductive contact with the connection contact.

A part of the circuit board can be made of the metallized plastic. The metallized plastic can either be designed as just a thin peripheral wall of the contact eye or it can cover an area of the circuit board. Finally, the entire circuit board could also be made of a plastic such as polyamide, with the metal material being applied to the surface by electroplating. On the other hand, the metallized plastic could also consist of a metal mesh inserted into the plastic material, so that the plastic as a whole is penetrated by a metal material.

A springy or elastic metal connection arm can connect the metallized plastic in the contact eye to the surrounding circuit board. The contact eye is connected to the circuit board on at least one side by the connection arm. The connection arm compensates to a certain extent for position and size tolerances between the peripheral wall in the contact eye and the rest of the circuit board.

There are now various possibilities for designing and developing the teaching of the present invention in an advantageous manner. For this purpose, reference is made on the one hand to the subordinate claims and on the other hand to the following explanation of an embodiment. They show, each in a schematic representation,

Fig. 1 a cross section through a circuit board with the contact eye

according to the present invention and

Fig. 2 a top view of the circuit board with the contact eye

according to the present invention.

The device for electrically contacting a connection contact 1 with a conductor track 2 on a circuit board 3 has a contact eye 4 arranged inside the circuit board 3. The conductor track 2 is guided to the contact eye 4 on the surface of the circuit board 3. A metal material in the form of a metallized plastic 6 is provided on the inner peripheral walls 5 of the contact eye 4.

The circuit board 3 is made of metallized plastic in the area of the contact eye 4. In the present embodiment, the metallized plastic is formed as a layer on the peripheral walls 5 of the contact eye 4 and on part of the surface of the circuit board 3. Alternatively, the circuit board 3 could also be made of plastic and the metal material could be provided as a surface coating using tin.

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The metallized plastic 6 consists of polyamide and a tin coating applied to it by electroplating. The contact eye is introduced as a stepped hole in the circuit board 3. In the area of the contact eye 4, the circuit board 3 is reinforced, i.e. made thicker in cross section. The connection contact 1 is introduced into the stepped contact eye 4 to create the connection, so that a first section 7 of the connection contact 1 engages with a first through section 8 of the contact eye 4 and a second section 9 of the connection contact 1 engages with a second through section 10 of the contact eye 4.

Between the passage sections 8 and 10 of the contact eye 4, an inclined ring step 11 is formed, which separates the two passage sections 8, 10. On both sides of the wall step 11, two independent electrically conductive connections are created between the connection contact 1 and the peripheral walls 5 of the contact eye 4.

As can be clearly seen in Fig. 2, when the connection contact 1 is inserted into the contact eye 4, the originally cylindrical peripheral wall 5 is bent into an approximately oval shape. This creates high contact forces on the narrow sides 12 of the connection contact 1 that deform the peripheral walls 5. When the connection contact 1 is inserted, slight plastic deformations therefore take place on the surface of the metallized plastic on the peripheral wall 5, which result in a connection that conducts electricity well.

Since the thickness, i.e. the cross-sectional height, of the circuit board 3 in the area of the contact eye 4 is greater than the thickness of the circuit board 3 in the remaining area and metallized plastic is applied to the inside of the peripheral walls 5, the large diameter of the through section 10 and the small diameter of the through section 8 can deform largely independently of one another and to different degrees. The deformation of the metallized plastic can also occur in a direction perpendicular to the surface of the circuit board. The deformed contact eye 4 then protrudes with its peripheral walls 5 over both the top and bottom of the circuit board.

The connection contact 1 is of stepped design. The connection contact has dimensions such that a type of press fit is created between the connection contact 1 and the contact eye 4. This advantageously fixes the connection contact 1 in the contact eye 4. The connection contact 1 has dimensions such that the narrow sides 12 plastically deform the metallized plastic to a small extent. The connection contact is slightly larger in a direction parallel to the circuit board plane than the diameter of the undeformed contact eye 4. A connection arm 13 is formed by the metal material, i.e. the metallized plastic, in order to provide a resilient transition to the rest of the circuit board 3 in order to compensate for position tolerances and size tolerances, in particular caused by the metallized plastic.

In order to prevent unintentional contact between the contact eye 4 and the surrounding electronics, a recess 14 is arranged in a ring shape around the contact eye 4. Finally, all edges and also areas of the ring step 11 on the connection contact 1 and on the contact eye 4 are preferably rounded.

Claims (18)

1. Device for electrically contacting a connection contact ( 1 ) with a conductor track ( 2 ) of a circuit board ( 3 ), the circuit board ( 3 ) having a contact eye ( 4 ) for receiving the connection contact ( 1 ) and the conductor track ( 2 ) being guided to the contact eye ( 4 ) on the surface or an intermediate layer of the circuit board ( 3 ), characterized in that a metal layer on the inner peripheral walls ( 5 ) of the contact eye ( 4 ) is in conductive connection with the conductor track ( 2 ) and the inner dimensions of the contact eye ( 4 ) are adapted to the outer dimensions of the connection contact ( 1 ) such that the connection contact ( 1 ) can be clamped into the contact eye ( 4 ). 2. Device according to claim 1, characterized in that at least the inner peripheral walls ( 5 ) of the contact eye ( 4 ) consist of a deformable plastic with a metallized surface. 3. Device according to one of claims 1 or 2, characterized in that the metal layer is applied to the surface of the plastic, in particular by galvanization. 4. Device according to one of claims 1 to 3, characterized in that the metal layer consists of tin or a tin alloy. 5. Device according to one of claims 1 to 4, characterized in that the plastic is polyamide. 6. Device according to one of claims 1 to 5, characterized in that the circuit board thickness increases in the region of the contact eye ( 4 ). 7. Device according to one of claims 1 to 6, characterized in that the contact eye ( 4 ) is plastically deformable in its cross section when the connection contact ( 1 ) is inserted. 8. Device according to one of claims 1 to 7, characterized in that the contact eye ( 4 ) decreases in cross-section in the insertion direction of the connection contact ( 1 ). 9. Device according to one of claims 1 to 8, characterized in that the contact eye ( 4 ) has an inner peripheral wall ( 5 ) with a wall step ( 11 ). 10. Device according to claim 9, characterized in that the contact eye ( 4 ) has a cylindrical passage in the circuit board ( 3 ) with an inner annular step ( 11 ). 11. Device according to one of claims 1 to 10, characterized in that the connection contact ( 1 ) is stepped in the longitudinal direction, so that it is limited in the insertion direction by the stepped contact eye ( 4 ). 12. Device according to one of claims 1 to 11, characterized in that the connection contact ( 1 ) is larger in one dimension of its cross section than the corresponding dimension, in particular the diameter, of the contacting eye ( 4 ). 13. Device according to one of claims 1 to 12, characterized in that the connection contact ( 1 ) has two opposite edges or narrow sides which cause a deformation of the contact eye ( 4 ). 14. Device according to one of claims 1 to 13, characterized in that the contact eye ( 4 ) has two passage sections ( 8 , 10 ) with different dimensions adjacent to a wall step. 15. Device according to claim 14, characterized in that the two through sections ( 8 , 10 ) deform when the connection contact ( 1 ) is inserted in such a way that the contact eye ( 4 ) projects beyond the circuit board ( 3 ) on the upper and/or lower side. 16. Device according to one of claims 1 to 15, characterized in that the contact eye ( 4 ) has insertion bevels and/or rounded edges arranged on the inside. 17. Device according to one of claims 1 to 16, characterized in that a part of the circuit board ( 3 ) is made of a metallized plastic. 18. Device according to one of claims 1 to 17, characterized in that a springy or elastic connecting arm made of metal connects the metallized plastic in the contact eye ( 4 ) with the surrounding circuit board ( 3 ).