WO1990007804A1

WO1990007804A1 - Process and device for connecting flexible strip conductors to connecting contacts

Info

Publication number: WO1990007804A1
Application number: PCT/EP1989/001619
Authority: WO
Inventors: Ernst Freund
Original assignee: Mst Micro-Sensor-Technologie Gmbh
Priority date: 1988-12-30
Filing date: 1989-12-29
Publication date: 1990-07-12
Also published as: DE3844420A1

Abstract

A process and a device are useful for connecting contacts of a first electronic component to contacts of a second electronic component. The components are aligned in accordance with the order of connection and bonded to each other by a hot-melt adhesive charged with electrically conductive particles which are not connected to each other in an electrically conductive manner. During the bonding process, the connection regions of the components are moved toward each other in such a way that only directly opposite contacts are connected to each other electrically by the conducting particles in the adhesive. The device for implementing the process comprises a clamping device for fixing the components in the predetermined order of connection and a strip heater which heats the connection regions in order to melt the adhesive. The process and device make it possible to produce rapid and reliable contact between contacts located a short distance apart.

Description

Method and device for "connecting flexible conductor tracks to connection contacts

The invention relates to a method for connecting a contact or a plurality of adjacent contacts of a first electrical unit to one or more contacts of a second electrical unit arranged in accordance with the connection grid of the first unit.

On the boards of compact electronic devices, which are generally densely populated with components, there is often only little space for rows of contacts, for example for connecting components or for connecting

Lines that connect the boards to peripheral circuits. Efforts are therefore made to make the contacts very small in such narrowly delimited connection zones and to arrange them closely next to one another. The same applies, for example, to the contacts on connecting strips of small digital displays, such as LCD displays of calculators, measuring devices, clocks and the like. For the connection of such components or circuit boards to peripheral circuits, flexible conductor strips are used, for example, on which flexible conductor tracks are arranged next to one another in accordance with the grid of the contact rows. The conductor tracks can be connected to the rows of contacts, for example, using so-called "zebras". A zebra consists of juxtaposed, alternating electrically conductive and non-conductive layers and is arranged between a row of contacts and the conductor tracks of a flexible conductor strip in such a way that the electrically conductive layers of the zebra connect the respective contacts and conductor tracks to one another. However, such zebra contacting is generally not suitable for contacts or conductor tracks small distances of less than 1 mm from each other, for example.

In addition, separate fastening parts or sockets are required to fix such connections.

Another possibility for contacting or connecting electrical units consists in soldering the respective contacts or connections to be connected to one another, but this is difficult to carry out in the case of contacts lying closely next to one another and is not very reliable with regard to mechanical strength and short-circuit protection.

The invention is based on the object of specifying a method of the type mentioned at the beginning, with the aid of which contacts of a first electrical component which are closely adjacent to one another are simply and reliably connected to contacts of a second electrical component which are arranged in accordance with the connection grid of the first component and which Units can be permanently attached to each other.

To achieve this object, it is proposed according to the invention that the connection zones of the structural units are aligned with one another and glued to one another in such a way that the respective contacts lie opposite one another and are connected to one another via the adhesive, and that one is bonded with electrically conductive, but not continuously, together used electrically conductive particles penetrated hot melt adhesive, whereby the hot melt adhesive is melted by temporary heating and during the hot melting and curing of the adhesive, the connection zones of the electrical units approach each other in such a way that the conductive particles of the adhesive merely electrically connect the respective opposing contacts to one another. The method according to the invention enables the contacting of very closely adjacent contacts of a first electrical component, such as a circuit board, with correspondingly closely adjacent contacts of a second electrical component, such as a flexible conductor strip, with very simple means. In addition, the adhesive ensures a firm and lasting cohesion of the building units. The size and distribution of the electrically conductive particles in the hot-melt adhesive is selected so that only the respective very close contacts are electrically connected to one another via these particles, without short-circuits occurring between the adjacent connections, even if they are one Only 0.2 mm apart.

A hot-melt adhesive thread drawn from the melt is preferably used for the adhesive, in which the electrically conductive particles are present as metal fibers and / or carbon fibers and / or soot particles, the length dimensions of which are, in particular <200 μm. Such adhesive threads are very easy to handle and ensure low adhesive consumption.

The invention further relates to a device for connecting a contact or a plurality of adjacent contacts of an electrical assembly, in particular a flexible conductor track, to one or more contacts of a second electrical assembly arranged in accordance with the connection grid of the first assembly, in particular. a circuit board.

With this device it is achieved according to the invention that the connection of contacts of two electrical units can be carried out very easily, quickly and precisely, and that even heat-sensitive units such as For example, a ceramic circuit board of a hybrid can be contacted without risk of damage.

The device according to the invention is characterized by a clamping device for fixing the structural units in a predetermined position relative to one another, with a base and with a support for pressing the connecting zones of the structural units against one another and by a controllable heating device with at least one heating tape that heats the pressed-together connecting zones for melting a hot melt adhesive interspersed with electrically conductive particles between the connection zones. With the clamping device, the connection zones of the structural units and an adhesive inserted between them can be pressed close together and fixed in a predetermined position relative to one another. The heating tape extends along the connection zones and touches one of the structural units on its side facing away from the contact side. During a heating process (heating pulse), the connection zones in the vicinity of the heating tape and the adhesive located between them are brought very quickly to a temperature melting the adhesive in order to initiate the adhesive process. After a heating impulse has elapsed, the poor becomes very effective from the surface and the support of the

Clamping device removed so that outside of

Areas of the structural units lying in the connection zones are not in the

Afterwards be heated excessively and the cooling time of the hot melt adhesive is kept short.

In a development of the device according to the invention, the base and the support are each designed as a web. In the clamping state of the clamping device, the webs and the heating tape run essentially parallel to one another, the support web being essentially exactly above the heating tape. With this arrangement or design of the pad, the heating tape and the support, the printing and The effect of temperature on the structural units to be connected to one another in the clamping device can be concentrated very simply on the spatially narrow connection zones. The supporting web and the supporting web are preferably dimensioned in such a way that they have a comparatively small heat capacity, which helps to shorten the heating and cooling times.

In a further embodiment of the invention, the base and the support are made of heat-resistant plastic or plastics, which in particular have small specific heat, so that the heat capacity of the base and the support is additionally kept small by the choice of material.

In a further embodiment of the invention, the support is arranged on a swivel arm pivotable about an axis. The swivel arm facilitates the operation of the device according to the invention and ensures precise guidance of the support when tensioning and releasing the clamping device.

According to further refinements of the invention, the heating power or heating duration of the heating device can be preset. The device is thus also easy to use by training personnel after the device has been adapted to the heat output or duration of the adhesive used and the parts to be connected to one another.

In a development of the device according to the invention, a temperature measuring device with a control circuit and a temperature sensor connected to it is provided for the temperature of the connection zones. As soon as the temperature sensor detects that a predetermined connection zone temperature has been reached, the control circuit interrupts the power supply to the heating tape. This can be a Overheating of the components to be connected can be safely avoided.

The temperature sensor of the temperature measuring device is preferably arranged on the base so that it does not interfere with the operation of the clamping device.

The heating tape is preferably provided on the base and is supported on the base when the structural units are pressed together.

For additional feeding of heat into the connection zones, at least one further heating tape of the heating device is preferably provided on the support. The further heating tape extends over the support surface of the support, so that - in the clamped state of the clamping device - the additional heating tape and the heating tape running over the base enclose the structural units between them and in particular lie exactly one above the other.

The invention is explained below using two exemplary embodiments with reference to the drawing.

It shows:

Fig. 1 is a simplified schematic plan view of the two embodiments arranged on a common carrier 2, 4,4 'and

FIG. 2 is a side view in section along line II-II in FIG. 1.

Reference is first made to embodiment 4 below. This exemplary embodiment is particularly suitable for connecting conductor tracks 6 of a flexible conductor strip 8 to contacts 10 of a circuit board 12, optionally one or two side by side

Contact rows 11 a board can be contacted simultaneously. A base web 14 made of a heat-resistant plastic and two heating bands 16 running parallel to one another above the base web 14 form a base for the circuit board 12. The spacing of the heating bands 16 from one another is selected such that it essentially corresponds to the distance between the two contact rows 11 on the base plate Board 12 corresponds. The board is placed on the heating tapes 16 and the web 14 so that the. Contact rows 11 lie on the circuit board side facing away from the heating tapes 16, parallel to the heating tapes and exactly above the heating tapes. A hot melt adhesive thread 20 is applied to the contact rows. The hot-melt adhesive is interspersed with electrically conductive particles, which, however, are not continuously connected to one another in an electrically conductive manner. The flexible conductor strip 8 to be connected to the circuit board 12 is then placed on the circuit board and aligned with the circuit board 12 in such a way that the conductor tracks 6 lie opposite the contacts 10 to be connected therewith. A support 26 guided on a swivel arm 25, which forms a clamping device 28 with the support 14, serves to fix this arrangement. The support 26 can be rotated about an axis of rotation 27 on the swivel arm 25 and has two support webs 30 which run parallel to one another and whose spacing from one another essentially corresponds to the spacing of the heating strips 16 from one another. To clamp the circuit board 12 and the conductor strip 8, the support 26 is pressed onto the flexible conductor strip 8, the webs 30 concentrating the pressure essentially on the connection zones. An adjustable stop (not shown) keeps the support 26 at a predetermined distance from the base 14.

The heating strips 16 are part of a controllable heating device (the further components of which are not shown) 2 and can be switched on or off together or individually. The heating current through the heating band or bands 16 is switched on manually and is automatically switched off by a control circuit of a temperature measuring device when the temperature sensor 32 of the temperature measuring device arranged on the base detects a predetermined temperature which exceeds the melting temperature of the hot melt adhesive threads 20. Excessive heating of the circuit board 12 or of the flexible conductor strip 8 can be avoided in this way.

As a protection against overheating, a heat sink 31 made of a good heat-conducting material (for example, a bronze sheet) is also provided, which outside the clamping device 28 with d. _he board 12 is in contact to dissipate heat.

The heating phase, in which heating is carried out with a comparatively high, essentially constant heating power, in order to melt the adhesive threads 20 in the region of the connection zones in the shortest possible time, is followed by a cooling phase in which the adhesive hardens. A signaling device is provided to signal that the cooling phase is complete, or that the temperature measured by the sensor 32 in the connection area of the circuit board has fallen below a predetermined value. The

Signaling device comprises a light-emitting diode 36 which is coupled to the temperature measuring device 32 and to the heating device. The light-emitting diode 36 turns on and off alternately during the heating phase and is switched off during the cooling or curing phase.

Outside of these two operating states, heating up and cooling down, the LED lights up to indicate readiness for a new sealing or gluing process. The operator of the device according to the invention can thus base his operating steps on the light-emitting diode 36 in order to avoid unnecessary waiting times when contacting larger quantities of boards or to avoid the like. This ensures that the adhesive hardens well at the end of the cooling phase and that the clamping device is accessible to the operator without the risk of burns.

After the cooling or curing phase, the flexible conductor strip 8 and the circuit board 12 are firmly and permanently bonded to one another and the conductor tracks 6 are electrically connected to the respective contacts via fine electrically conductive particles in the adhesive, without short circuits occurring between adjacent connections or contacts . This is because the distance between the opposing contacts (6, 10) is small enough, for example, to be bridged by individual electrically conductive particles of the adhesive 10, whereas the distances between the adjacent connections for such bridging by the conductive ones Particles are too large.

The second exemplary embodiment 4 'is intended in particular for the contacting of units with terminal strips, such as small digital displays 5'. Such digital displays '5' generally have a narrow circuit board strip 12 'on which the connection contacts 10' are arranged closely next to one another, for example in a grid with only 0.5 mm grid spacing.

The construction of the device 4 'is similar to that of the device 4 and also comprises a base web 14', a heating tape 16 'and a guide arm 25' which can be guided

Support rail 30 '. In addition, the device 4 'has an adjusting and holding device 17'. The adjusting and holding device 17 'comprises a seat 19' with a leading edge 21 'for the digital display 5' and an adjusting screw 23 'with which the digital display 5' can be moved against the force of a spring 24 'along the leading edge 21', around the contacts 10 'in the Bring contact position relative to the conductor tracks 6 'of a flexible conductor strip 8'. The conductor track 6 'in turn is fixed in its position, which is indicated by two lateral contact strips 18' in the figures. The board bar 12 'is on the above

Base web 14 'running heating tape 16'. The clamping device 28 'formed from the support web 14' and the support web 30 'presses the circuit board strip 14', the flexible conductor strip 8 'and the adhesive thread 20' between them tightly during the gluing process. In contrast to the previously described device 4, the device 4 'has only one heating band 16' and one support web 30 '. As a result, a temperature measuring device with a temperature sensor arranged on the base web 14 'is not possible in the device 4'. In the device 4 ', the heating time is determined by an adjustable time circuit (not shown). During this heating period, heating is carried out with a substantially constant, comparatively high heating output. A light-emitting diode 36 ^r controlled by the time switch signals the heating phase and a predetermined cooling phase.

Both devices 4, 4 'according to the invention are designed such that the melting temperature of the adhesive in the area of the respective contact zones is reached comparatively quickly, for example in 10 to 20 seconds, without areas of the circuit board or terminal strip lying outside the contact zones being heated excessively . This is achieved in that the respective heating tape heats up the contact zones with a comparatively large heating output only in a locally narrowly limited area, and in that the supporting webs 14, 14 'and supporting webs 30, 30', which are designed with small heat capacities, represent only a low thermal load and after the heating phase has ended, remove the heat from the circuit board or the flexible conductor strip carrier. In a preferred variant of the exemplary embodiments described above, heating tapes 40, 40 '(shown in dashed lines) are also provided on the support 26, 26'. These further heating strips 40, 40 'run along the webs 30, 30' on their bearing surface. When the structural units 8, 12 or 8'12 'are clamped in the clamping device 28 or 28', the heating bands 16 and 40 or 16 'and 40' close the structural units 8, 12 or 8 ', 12' between themselves. The heating power of the further heating tapes 40, 40 'is controlled in particular in accordance with the control of the heating power of the heating tapes 16 and 16'.

The method according to the invention is not limited to the connection of circuit boards with flexible conductor strips, but is also suitable, for example, for the direct connection of contacts of electrical or electronic components to the contacts of a circuit board.

Claims

Method for connecting a contact or a plurality of adjacent contacts of a first electrical component to one or more contacts of a second electrical component arranged according to the connection grid of the first component, characterized in that the connection zones of the components (8, 12; 8 ', 12' ) aligned and glued to each other in such a way that the respective contacts (6, 10; 6 ', 10') face each other and are connected to each other via the adhesive (20; 20 '), and that one is glued with electrically conductive, but not Hot melt adhesive (20; 20 ') which is continuously connected to one another in an electrically conductive manner is used, the hot melt adhesive (20; 20') being melted by temporary heating and

during the hot melting and curing of the

Adhesive (20; 20 ') approaches the connection zones of the electrical assemblies (8, 12; 8'12') in such a way that the conductive particles of the adhesive (20, '20') only the contacts (6, 10; 6 ', 10').

2. The method according to claim 1, characterized in that one for connecting the connection zones

Hot melt adhesive thread (20; 20 ') used, in which the electrically conductive particles are distributed as metal fibers and / or carbon fibers and / or soot particles.

Method according to Claim 1 or 2, characterized in that a flexible printed circuit board (8; 8 ') is used as at least one of the structural units.

4. Device for connecting a contact or a plurality of adjacent contacts of a first electrical unit, in particular a flexible conductor track, to one or more in accordance with the connection grid of the first

Contacts arranged in a structural unit of a second electrical structural unit, in particular a printed circuit board, in particular for carrying out the method according to one of the preceding claims, characterized by a clamping device (28; 28 ') for fixing the structural units (8, 12; 8', 12 ') in one predetermined position to each other, with a base (14; 14 ') and with a support (26; 26') for pressing the connection zones of the units (8, 12; 8; i2 ') against each other, and by a controllable heating device with at least one to each other Λ-λ pressed connection zones of the units

(8,12; 8 ', 12') heated heating strip _(16/16 ') for melting a interspersed with electroconductive particles Heizschmelzklebers (20; 20') between the terminal zones.

5. The device according to claim 4, characterized in that the base (14/14 ') and the support (26, * 26 ^τ ) are each designed as a web, wherein in the clamped state of the clamping device (28/28') of the support web (30 / 30 '), the support web (14/14') and the heating tape (16-16 ') run essentially parallel to one another and the support web (30/30') is essentially exactly above the heating tape (16/16 ').

6. The device according to claim 5, characterized in that the width of the support web (30-30 ') corresponds substantially to the width of the heating tape (16; 16').

7. The device according to claim 4, 5 or 6, characterized in that »the support (26/26 ') and the base (14; 14') are made of heat-resistant plastic.

8. Device according to one of claims 4 to 7, characterized in that the support (30/30 ') on a pivotable about an axis pivot arm (25/25') is arranged.

9. Device according to one of claims 4 to 8, characterized in that the heating power of the heating tape (16; i6 ') can be preset. 10. Device according to one of claims 4 to 9, characterized in that the heating duration of the heating tape (16/16 ') can be preset.

11. The device according to one of claims 4 to 10, characterized by a temperature measuring device with a control circuit and a temperature sensor (32) connected thereto for the temperature of the connection zones in the vicinity of the heating tape (16), wherein the control circuit

Power supply to the heating tape (16) is interrupted when the sensor (32) detects that a predetermined connection zone temperature has been exceeded.

12. Device according to one of claims 4 to 11, characterized in that the heating tape (16/16 ') outside of the area to be glued is made wider to reduce the heating power.

13. Device according to one of claims 4 to 12, characterized in that the heating strip (16; 16 ') on the base (14 ^' ? 14 ') is provided.

14. The apparatus according to claim 13, characterized in that a further heating tape (40; 40 ') is provided on the support (26; 26').