GB2341485A

GB2341485A - Electrical connection technique for contact pins

Info

Publication number: GB2341485A
Application number: GB9919803A
Authority: GB
Inventors: Bernd Taubitz; Dietmar Rischen; Marcus Kristen; Thomas Gramkow; Ewald Spiess
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1998-09-04
Filing date: 1999-08-23
Publication date: 2000-03-15
Anticipated expiration: 2019-08-23
Also published as: ITMI991830A0; FR2783106B1; IT1313114B1; FR2783106A1; DE19840305A1; GB2341485B; ITMI991830A1; GB9919803D0

Abstract

A method of automatically electrically and mechanically interconnecting the ends of pins 2 of an electronic device and conducting strips 3. A locating strip 5 having bores 6 is placed over the pins. The conductors are aligned with the ends of the pins using reference marks 9 and 10 and then a laser bonding device impinges on the conductors, on the side opposite to the pins, to form the bond. Insulating cross pieces 13 may be provided between conductors. The pins may be gold plated. The position of pins ends may be detected and recorded by an optical device before the laser bonding is carried out.

Description

2341485

DESCRIPTIO ELECTRICAL CONNECTION TECBMQUE FOR CONTACT PINS

Tle invention relates to a method of producing a connection between contact pins and electrical conductors, wherein the conductors are positioned on to the contact pins and a connection-producing device acts upon the conductors from the side lying opposite the contact pins.

In the automotive industry, for example in the case of transmissions in motor vehicles which have a step-wise variable automatic transmission, highly-integrated electronics are disposed in the region of the transmission. The control electronics are integrated, for example, in a metallic, hermetically sealed electronics housing. The electrical connection to sensors, the current source or other control devices is produced by way of electrical conductors which must be connected in an electrically conductive manner to contact pins of the electronics housing. The electronics housings are often designed in the form of a microprocessor housing so that contact pins disposed on the underside in several rows are provided.

When producing electrically conductive, preferably non-releasable connections, the disadvantage arises that owing to the deviations and tolerances, primarily in conjunction with the contact pins, it is difficult to perform the connection procedure in an automated manner. Primarily, if the conductor tracks are to be welded directly on to the end face of the exposed ends, there is the risk that the connection- producing device, for example a laser welding device, produces the laser 2 weld point in an offset manner with respect to the end face of the contact pins, so that it is either the case that no electrical connection is produced at all or the quality thereof is poor.

It is an object of the present invention, to guarantee a high degree of quality and reproducibility in the process of producing the connection, so that it is possible for the connection procedure to be automated.

In accordance with the present invention, an alignment procedure is provided, in order to implement the procedure of producing the connection on the conductor track in a precise manner with respect to the free end of the contact pins.

It was recognised in accordance with the invention that, during an alignment procedure, the conductor tracks are to be aligned in a precise manner with respect to the respective free end of the contact pins prior to the actual process of producing the connection. On the one hand, the alignment procedure can provide that the contact pins are aligned precisely with respect to the spacing by way of a locating strip. In particular, this is required if the contact pins have been embedded within inlays into individual glass through-passages in an electronics housing and have become bent with respect to the ideal position of their own accord or by reason of a mechanical effect.

On the other hand, the alignment process can also affect the position of the connection-producing device, for example, a welding device. The welding device is then aligned in a precise manner with the respective end face of the free ends of the contact pins, so that it is possible to produce a connection in the precise location. The 3 alignment process produces a high degree of alignment accuracy and reproducibility in the connection procedure. In this manner, the connection procedure can be automated, for example, by means of a welding device. Owing to the exact alignment, electrical conductors can be welded in a particularly advantageous manner directly on to the end faces of the free ends of the contact pins.

In the case of an embodiment of the method in accordance with the present invention, particularly small or negligible mechanical stresses are produced in the contact pins during the connection procedure with respect to glass fusion sealing arrangements on the electronics housing.

By reason of the extremely precise alignment process of either the contact pins, the conductor tracks or the connection-producing device, the connection site is produced exactly on the free ends of the contact pins and the corresponding conductor track, so that a high degree of mechanical strength is produced at the weld site, wherein the holding forces of the connection correspond approximately to a weld connection having the cross-section of the contact pins. A particularly compact connection technique is produced in the method, if the connection sites are disposed in proximity to the electronics housing and have a small installation volume.

In the case of an advantageous method step, contact pins which, prior to the production of the connection. are coated with a reflective material, preferably gold, are concealed from the connection-producing device by the conductors during the production of the connection. With respect to a method step of a glass fusion sealing or bonding process on the inner side of an electronics housing, the surface of the 1 4 contact pins has to be coated, preferably gold-plated. In this manner, the contact pins can be connected with one side to the electronics housing and the control electronics disposed therein. For the sake of simplicity, in the main the entire surface of the contact pins is gold- plated. In conjunction with a laser welding process, the gold layer acts like a mirror and reflects the laser beam. By virtue of the fact that the conductors conceal the gold layer from the laser welding device during the process of producing the connection, i.e. during the laser welding process, the energy reduction associated with the reflection is completely eliminated during the welding procedure.

In the case of a further advantageous method step, a fuse connection is produced between the contact pins and the conductors, wherein the conductor is fused from the side remote from the contact pin and the fuse energy is transmitted further to the contact pin. In this manner, the accessibility of the weld site is only required from one side. The laser welding device acts upon the conductors merely from the side lying opposite the contact pins, so that as a consequence gold-plated pins can be laser welded without experiencing any problems. If the conductors are formed as two-dimensional conductors, preferably as punched grid conductor tracks, the goldplated contact pin is advantageously covered by said punched grid conductor tracks, so that the reflection effect does not occur during the laser welding process.

In the case of a different advantageous method step of the present invention, a locating strip is positioned on to the contact pins during the alignment process, whereby the free ends of the contact pins are aligned with a spaced interval. The electronics housing can comprise, for example, contact pins which are disposed in two rows. The contact pins are disposed preferably in a centrally offset manner with respect to each other within so-called inlays. The individual pins can have a diameter of, for example, 0.6nun and a length of 7mm. The pins are embedded within the inlays into individual round glass through-passages and are thus hermetically sealed. The contact pins comprise on the free end preferably one flat end face, i. e. they are cut in a straight manner from a wire during the manufacturing process. Ile contact pins are disposed within the inlays at a uniform spacing, so that, for example, the distance from one contact pin to another contact pin of a row amounts to 5MM.

With respect to the spacing, the ends of the contact pins, i.e. the end faces, can have several tenths of a millimetre tolerance with respect to each other caused by the glass fusion sealing process. Furthermore, further deviations arising from subsequent mechanical influences cannot be discounted. The ends of the pins must therefore be aligned with respect to the spacing in a relatively precise manner prior to the welding procedure and must be secured in this state. For this purpose, a locating strip consisting of insulating synthetic material can be pressed on to the contact pin row. Advantageously, funnel-shaped bores within the locating strip simplify the process of introducing and aligning the contact pins with an extremely low tolerance. In order to achieve an effective weld connection, it is a prerequisite that the laser beam impinges in the most precise manner possible on the central middle of the contact pins which are not visible to the connection-producing device, for example, the laser welding device, so that a high-quality connection is produced.

6 After the connection has been produced, the locating strip can remain positioned on the contact pins and ensures the contact pin spacing in the region of the end faces of the contact pins. The contact pins and conductors are mutually insulated in the region of the connection site by virtue of insulation cross-pieces on the locating strip. As a consequence, contact pins positioned narrowly apart and punched grid conductor tracks lying close together are insulated in an advantageous manner by virtue of vertical synthetic material cross-pieces on the locating strip.

In the case of a preferred method step, during the process of connecting the conductors to the free ends of the contact pins, a travel limiting means prevents mutual penetration, in particular during the fusion connection process, or prevents the conductors from becoming displaced with respect to the contact pins. The travel limiting device for the conductors, in particular the punched grid conductor tracks, is important for forming the weld site in an effective manner during the welding process. During the welding process, the following effect occurs: the welding energy, for example, from the laser welding device, serves to fuse the respective punched grid conductor track and for a short period of time it appears as if a hole is provided therein. Without limiting the travel, the contact pin passes at this moment through the punched grid conductor track in an uncontrolled manner, so that it is not possible to form an optimum weld connection. By virtue of the travel limiting device, the respective conductors occupy an ideal position with respect to the corresponding contact pins.

It is preferred to provide a stop, especially an edge or surface on the locating 7 strip, whereby the conductors are prevented from sinking down. The fusing conductors, preferably punched grid conductor tracks, can then sink down into the contact pins oniy by way of a predefined patl; in parallel with the longitudinal direction of said contact pins, so that it is possible to maintain a precisely predetermined connection position between the contact pin and conductor. If, for example, the pin end faces jut out approximately 0.2mm beyond the locating strip, the punched grid conductor tracks sink down by precisely this distance into the contact pins, until they stop on the locating strip.

In the case of a further preferred method step, the conductors are biassed in the direction of the locating strip during the alignment process and consequently sink down during the fusion procedure as far as a stop ofthe locating strip into the contact pins, By virtue of the biassing, the conductors assume a defined connection position.

In so doing, a so-called overlapping connection is produced between each contact pin and the corresponding conductor. %.

In the case of a different advantageous. method step, the conductors are disposed, during the aligronent process, at a spaced interval with respect to the ends of the contact pins and, where appropriate, with respect to the locating strip, a plurality of conductors are pressed by virtue of a pressing strip against the end faces of the free ends of the contact pins and during the fusion process a conductor is prevented from sinking down by virtue of the restoring force of the conductor away from the contact pins. The restoring force is produced by virtue of the fact that the conductors are disposed at a spaced interval, in parallel with the longitudinal 8 direction of the contact pins opposite same. Since the pressing strip lies on the adjacent conductors which are pressed on to the contact pins and at that moment are not yet involved in the fusion connection process the pressing strip remains fixed in position. In this manner, the conductor is prevented from sinking down, during the process of producing a connection in a fusing conductor, by virtue of the pressing strip which lies on the ends of adjacent conductors. Limiting the travel in the direction with respect to the contact pins is therefore achieved by virtue of the pressing strip in conjunction with the restoring forces of the conductors and limiting the travel away from the contact pins is achieved directly by virtue of the pressing strip. As a result, a weld connection is produced with contact pins and conductors in a precisely predetermined position.

During the alignment process the contact pins and the conductors can be disposed at a spacing of some tenths of a millimetre with respect to each other and by virtue of the pressing strip the punched grid conductor tracks can be pressed against the end faces of the free ends of the contact pins. The travel of the pressing strip or the punched grid conductor tracks is limited in this case by virtue of the adjacent contact pins. Since during the laser welding process the contact pins are preferably welded individually, the respective remaining, welded or nonwelded, contact pins serve as a stop for the purpose of providing uniform support. The respective contact pin cannot sink into the punched grid conductor track during the welding process, so that a non-overlapping installation position is produced.

In order to form the weld site in an improved manner, a space in the form of 9 a chamfer or stepped bore can be provided on the outlet sites of the contact pins on the locating strip(s). The diameter of the space is ca. Imm to 1.5mm deep. If the electronics housing has a plurality of pin rows, the locating strips can also be formed in one piece. The locating strips can also be a part of an electronics housing consisting of synthetic material which also serves, for example, to cool the electronics with cooling oil.

In the case of a flu-ffier advantageous method step the alignment process is performed on the basis of reference marks which are provided, in particular, on the electronics housing or the locating strip. It is provided that the connection-producing device is aligned in a plane perpendicular to the longitudinal direction of the contact pins, in order to be able to act in the most central manner possible upon the planar end faces of the pins during the process of producing the connection.

In accordance with an embodiment of the invention, the arrangement of the free ends of the contact pins is detected in a measuring procedure preferably as a contact pin plan having X and Y values. The connectionproducing device is moved during the alignment process to the positions of the end faces of the contact pins which positions are indicated in the measuring procedure. This method can be applied in particular if the contact pins can no longer be bent straight, i.e. cannot be aligned precisely with the spacing owing to their strength or mechanical stability. The contact Pins then remain in the original state in which they find themselves, for example, after the glass fusion sealing or bonding process. It is possible to implement an advantageous process of producing the connection by way of the measuring procedure followed by the process of aligning the connection- producing device. The position of the contact pins is recorded by a measuring optical device and the contact pin image is stored in the form of XlY values. During the laser welding process, the respective end face middle of a contact pin is then approached via the stored X and Y values. As already described, the zero point can possibly be marked by way of reference marks on the base of the electronics housing.

A different method step can be used in conjunction with contact pins which after being glass fusion sealed or bonded to the electronics housing can no longer be aligned precisely with the spacing. The contact pins are then slightly bent or warped and the end faces of the free ends of the contact pins are slightly offset with respect to the spacing. Initially, a locating strip having enlarged bores for the contact pins can be positioned on said contact pins, and during the subsequent welding procedure can thereby be used as a travel limiting device. In conjunction with a mechanical connection between the conductors the conductors can, on the other hand, also be aligned with respect to the contact pins.

Irrespective of whether the contact pins are provided with a locating strip, an alignment system is able on the one hand to detect the position of the end faces of the free ends of the contact pins and secure same in the contact pin plan and in addition detect the position of solder or weld eyes of the conductors. Subsequently, if tolerances are present in a plane perpendicular to the longitudinal direction of the contact pins between the end face of a contact pin and the middle of the weld or solder eye, the alignment system can align the connection-producing device in such a manner that an optimum connection is produced.

The alignment system can ensure that the connection site, for example, the laser weld point, is disposed half way between the middle of the weld or solder eye and the middle of the end face of the free end of the contact pins. On the other hand, the alignment system can also ensure that the laser weld point is disposed exactly above the end face of the contact pins, but disposed on the punched grid eye outside the middle.

The method of producing the connection can also be a specific soldering method, for example, a laser soldering method.

The invention is described further hereinafter, by way of example only, with reference to the accompanying drawings, in Which:- Figure 1 is a view, cut along the line of section I-I in Figure 2, of an electronics housing having contact pins and a locating strip in position, Figure 2 is a view from below of the electronics housing having punched grid conductor tracks and locating strips, Figure 3 is a view, cut along the line of section Ill-III in Figure 4, of an electronics housing having contact pins and a locating strip in position, and 17 12 Figure 4 is a view from below of the electronics housing having punched grid conductor tracks and locating strips.

In accordance with an embodiment of the method of the present invention, a non-releasable connection is to be produced between the contact pins 2 of an electronics housing 1 and associated punched grid conductor tracks 3. During the step in the process of being glass fusion sealed or bonded to the electronics housing 1, the contact pins 2 are embedded with one end, for example, within glass throughpassages which are recessed in inlays 4 in the electronics housing 1. The surface of the contact pins 2 is preferably gold-plated beforehand for the method step of glass fusion sealing or bonding, which owing to the reflection effect renders it more difficult to apply a direct laser welding method or alternatively a laser soldering method.

In the present case, punched grid conductor tracks 3 are used, for example, comprising a width of 1.6mm and a sheet metal thickness of approximately 0Amm. By virtue of the two-dimensional punched grid conductor tracks 3, the gold layer of the contact pins 2 is not visible to the laser welding device. The laser welding device acts upon the punched grid conductor tracks 3 from the side remote from the contact pins 2.

The laser beam initially impinges on the punched grid conductor tracks 3 and causes these to fuse partially. The fuse energy is then transmitted further to the corresponding contact pin 2, whereby said contact pin is fused and the weld 13 connection is produced. However, a prerequisite for a good weld connection is that the laser beam impinges in the most precise manner possible on the central middle of the contact pins 2 which are out of sight.

For this purpose, an alignment process is provided, wherein several possible, alternative method steps can be implemented.

In the case of a first alignment process, the contact pins 2 are aligned precisely with the spacing by virtue of a locating strip 5 having bores 6 for the purpose of receiving the contact pins, and having a fi=el-shaped entry region 7. The contact pins 2 are aligned by pressing the locating strip 5 on to the row of the contact pins 2 and by the conically tapering, funnel-shaped entry region 7 of the bores 6. After the alignment process, the punched grid conductor tracks 3 are preferably attached by biassing in the direction of the contact pin end faces 8. Reference marks 9, 10 enable the connection-producing device to be aligned in a precise manner with the position of each individual contact pin end face 8 by way of the contact pin plan having X and Y values and the laser weld point can be produced at the desired site.

In the case of an alternative alignment process, the punched grid conductor tracks 3 and the connection-producing device can both displaced in a plane perpendicular to the contact pins 2 in such a manner that the punched grid conductor tracks 3 and the contact pin end faces 8 can overlap and the weld connection can be arranged in an optimum manner.

In the case of a different alignment process, the punched grid conductor tracks 3 are aligned in a direction parallel with the longitudinal axis of the contact pins 2.

14 In order to produce the electrically conductive connection illustrated in Figures 1 and 2, the punched grid conductor tracks 3 are biassed in the direction of the contact pin end faces 8, so that upon fusing the punched grid conductor tracks 3 in the region of the punched grid eyes 11 it appears for a short period of time as if a hole is present in the punched grid eye 11. By virtue of the biassing, the corresponding contact pin 2 sinks into the biassed punched grid conductor track 3 and stops at the stop surface 12 of the locating strip 5. The stop surface 12 serves as a travel limiting device, in order to provide a desired, overlapping installation position of contact pins 2 and punched grid conductor tracks 3.

In the case of the connection which is illustrated in Figures 3 and 4 and is produced using a second alignment process in accordance with the present invention, the punched grid conductor tracks 3 have a spacing with respect to the stop surface 12 of the locating strip 5 and the connection between the contact pins 2 and the punched grid conductor tracks 3 is not overlapping, i.e. the contact pins 2 penetrate the punched grid conductor tracks 3 only slightly and certainly not completely. In the method, the punched grid conductor tracks 3 are disposed at a small spaced interval above the contact pin end faces 8 and are pressed on to the contact pin end faces 8 by means of a pressing strip. This produces a restoring force in the punched grid conductor tracks 3 in the direction of the pressing strip or away from the contact pin end faces 8. If, during the welding process, the material of a specific punched grid eye 11 of a punched grid conductor track 3 is softened, then by reason of the restoring force the punched grid conductor track 3 does not penetrate into the contact _1 pin 2, but rather a non-overlapping laser weld connection is produced.

The punched grid conductor tracks 3 can be mutually insulated by insulating cross-pieces 13 on the upper side of the locating strip 5. This is particularly advantageous, since the punched grid eyes 11 are disposed at a spaced interval with respect to the stop surface 12 of the locating strip 5 and could be displaced to a slight extent laterally, for example, in the event of mechanical stressing.

16

Claims

1. A method of producing a connection between contact pins and electric conductors, wherein the conductors are positioned on to the contact pins and a connection-producing device acts upon the conductors from the side opposite the contact pins, an alignment process being used, in order to implement the process of producing the connection on the conductor track with respect to the free ends of the contact pins.

2. A method according to claim 1, wherein, prior to the process of producing the connection, the contact pins are coated with a reflective metal, such as gold, and during the process of producing the connection this metal layer is concealed from the connection-producing device by the conductors.

3. A method according to claim 1 or 2, wherein the connection is produced by virtue of a laser welding device.

4. A method according to any of claims 1 to 3, wherein a fuse connection is produced between the contact pins and the conductors, the conductor being fused from the side remote from the contact pin and the fuse energy being transmitted further to the contact pin.

17 5. A method according to any of claims 1 to 4, wherein two-dimensional conductor tracks, such as punched grids, are used as the conductors.

6. A method according to any of claims 1 to 5, wherein during the alignment process a locating strip is positioned on to the contact pins, whereby the free ends of the contact pins are aligned with the spacing.

7. A method according to claim 6, wherein the locating strip remains in position on the contact pins after the process of producing the connection.

8. A method according to any of claims 6 or 7, wherein the contact pins and conductors are mutually insulated in the region of the connection site by virtue of insulating cross-pieces of the locating strip.

9. A method according to any of claims 1 to 10, wherein a travel limiting means, such as a stop or a pressing strip, serves to preset the position of the contact pin and associated conductor in the produced connection.

10. A method according to claim 9, wherein a stop, such as an edge or a surface of the locating strip, limits the extent to which the conductors sink down.

11. A method according to any of claims 9 or 10, wherein during the alignment 18 process the conductors are biassed in the direction of the locating strip and during the fusing process sink down into the contact pins as far as a stop of the locating strip.

12. A method according to any of claims I to 9, wherein during the process of producing the connection, a fusing conductor is prevented from sinking down by virtue of the adjacent conductors lying on the ends of adjacent contact pins.

13. A method according to any of claims I to 9 or 12, wherein during the alignment process the conductors are disposed at a spaced interval with respect to the locating strip and the ends of the contact pins, several conductors are pressed by virtue of a pressing strip against the end face of the free ends of the contact pins and during the fusing process a conductor is prevented from sinking by biassing the conductor away from the contact pins.

14. A method according to any of claims I to 13, wherein reference marks, preferably on an electronics housing and/or the locating strip, render it possible to align in a precise manner the connection-producing device with respect to the free ends of the contact pins.

15. A method according to any of claims I to 14, wherein during a measuring 19 procedure, the arrangement of the free ends of the contact pins is detected, for example as a contact pin plan having the X and Y values thereof 16. A method according to claim 15, wherein during the alignment process, the connection-producing device is moved to the positions indicated in the measuring procedure.

17. A method of producing a connection between contact pins and electric conductors, substantially as hereinbefore described, with reference to the accompanying drawings.