IE922333A1

IE922333A1 - Process for production of an adhesive joint between at least¹one building component and a metallic substrate

Info

Publication number: IE922333A1
Application number: IE233392A
Authority: IE
Inventors: Dipl-Ing Egon Edinger; Dipl-Ing Gerd Kohler
Original assignee: Mannesmann Ag
Priority date: 1991-07-19
Filing date: 1992-07-17
Publication date: 1993-01-27
Also published as: DE4124053A1; WO1993002538A1

Abstract

Electronic components like semiconductor chips or the like, in particular, are secured to the metallic substrate in practice by adhesion. According to the invention, the adhesive joint is produced by the use of a heat-acitvated adhesive film (2) between the items to be joined. The process is preferably applied in the assembly of ink-jet printing heads, in which the items to be joined are an aluminium plate (1) as the metallic substrate and the components consisting of a printed circuit board (3) and a jet module (4). The production process can thus be easily automated.

Description

Process for the production of an adhesive joint between at least one component and a metallic substrate.

The invention relates to a process for the production of an adhesive joint between at least one component, in particular an electronic component such as a semiconductor chip or the like, and a metallic substrate, components and metallic substrate being mutually joined by adhesive bonding as complementary parts.

In many fields of engineering, it is necessary to produce an adhesive joint between individual components. This has to be done as part of the manufacturing procedure, in which, for example, a semiconductor chip has to be mounted in a precise position, for example on a metallic substrate.

Such adhesive joints can in principle be achieved in a simple implementation by adhesive bonding. For this purpose, for example, epoxy adhesives are known in practice and these contain components which can be cured using UV light and/or by means of heat. Such adhesives may be applied to metallic substrates in a simple manner by screen printing.

A ease of the application of the abovementioned process engineering is the assembly of ink printing heads. In this case, in particular, a printed circuit board, on the one hand, and a so-called jet module, on the other hand, have to be bonded to an aluminium plate with positional accuracy. In this connection, the printed circuit board effects the interface with the computer for generating the control signals for the purpose of activating the jet module. The jet module is connected electrically to the printed circuit board by bonding wires. The entire modular unit is joined mechanically to an ink feedstock housing, and this has also being done hitherto by adhesive bonding. In this connection, an important additional requirement is that the adhesive joint produced is resistant to ink and that no ink comes into contact with the aluminium plate.

Hitherto, adhesive bonding techniques using epoxy adhesives have been used for the above problem. In the known process, after the adhesive has been applied to the aluminium plate, the printed circuit board and the jet module are positioned and then the bonding is activated, which is done by irradiation with UV light and subsequent curing in a heat-treatment oven.

The process specified has proved satisfactory in practice. However, it is unsatisfactory that the assembly described for ink printing heads is comparatively timeconsuming. Efforts are therefore made to accelerate the manufacturing procedure. In this connection, however, the following weak points emerge; the fixing of the printed circuit board and the jet module using UV light enters serially into the cycle time.

- For conventional adhesives, the curing time in the heat treatment oven requires approximately 30 min, thereby making large oven capacities necessary.

- The curing time interrupts the manufacturing flow and consequently prevents so-called just-intime” process controls.

- In screen printing the photosensitive adhesive, the screen printability may vary.

- The known adhesives may present problems because of qualitative differences in their potlife and in handling.

The approach generally adopted in a further 30 development is therefore to find for the particular application case an optimum adhesive which fulfils the specifications and whose handling has been optimised. However, for high piece numbers, the manufacturing process described is not sufficiently amenable to automa35 tion for basic reasons.

The object of the invention, on the other hand, is to provide a process for the production of an adhesive joint which is amenable to automation and can be incorporated in an integrated manufacturing process in an optimum manner.

The object is achieved, according to the invention, by the use, between the complementary parts to be bonded, of an adhesive film which reacts as a result of heat. Such a film is referred to as heat-sealing adhesive film and is known in the art of bonding. Specifically, the object is achieved by the application of the heatsealing adhesive film in the assembly of ink printing heads, in which assembly the complementary parts to be bonded are an aluminium plate as metallic substrate and, as components, a printed circuit board, on the one hand, and a jet module, on the other hand.

The invention results in comparatively short processing times as part of an integrated manufacture since the complementary parts to be bonded can be brought rapidly to the bonding temperature. A subsequent heat treatment of the bonded joint is not necessary. The final strength is reached immediately after cooling.

As part of the invention, the metallic substrate is heated in order to heat the complementary parts to be bonded for the purpose of producing the bonded joint. Preferably, the metallic substrate may be heated in a contact-free manner, in particular by high-frequency induction. Such a heating is advantageously carried out in a controlled manner, i.e. with precise adjustment to a temperature which is suitable for the specific adhesive film.

As part of the invention, heat-sealing adhesive foils can be used whose polymerisation is accelerated by exposure to high-frequency energy. Such heat-sealing adhesive films are composed, for example, of a mixture of phenolic resin and nitrile rubber and can be produced as thin films, in particular with a thickness of less than pm. Such films can be applied in a simple manner to the metallic substrate, for example by cladding, which substrate has furthermore to be degreased for the purpose of bonding. Because of the thin film, this arrangement Έ922333 results in a particularly good heat transfer from the component to the metal substrate.

All in all, the use of heat-sealing adhesive foils results in the advantage of an appreciable improvement in the ease of use in comparison with known epoxy adhesives. In particular, the assembly of ink printing heads becomes more amenable to automation as a result.

Further details and advantages of the invention 10 emerge from the description given below of an exemplary embodiment with reference to the drawing. The two figures show, in the plan view and in the section along the line II-II a product design, suitable for automation, of an ink printing head in which the printed circuit board and jet module are assembled by adhesive bonding. Both figures are described together.

In Figures 1 and 2, an aluminium plate is denoted by 1. A printed circuit board 3 and a jet module 4 are bonded to the aluminium plate by means of a heat-sealing adhesive film 2. The printed circuit board is an interface between a computer for driving the ink printing head and has so-called contact pads. For the automated production of bonded joints, therefore, a precise position of the printed circuit board 3 with the contact pads is necessary, and this is achieved by the adhesive bonding. In this state, bonded joints 5 can be produced between printed circuit board 3 and jet module 4, tested and potted. This immediately results in a complete functional module for the further assembly of the ink printing head.

The finally assembled functional module in accordance with Figure 1 is mounted on the ink housing, which is not shown, by hot rivetting. An 0-ring seals the ink with respect to the housing and to the aluminium plate 1. An additional bonding of the aluminium plate 1 to the ink housing can then be omitted.

From Figures 1 and 2 it is evident that the functional module is situated inside an inductor loop 10.

As a result of high-frequency induction via the inductor loop 10, the aluminium plate 1 can be heated in a controlled manner, a suitable sensor (not shown) being disposed on the aluminium plate 1 for the purpose of tem5 perature measurement.

The process described, which uses the heatsealing adhesive film, is highly amenable to automation: the rapid heating by means of high frequency and subsequent cooling of the complementary parts to be bonded results in short cycle times in the range from 5 to 10 sec. A subsequent heat treatment of the bonded joint is no longer necessary: the final strength is reached immediately after cooling.

It is particularly advantageous that, after the production of the bonded joint, the functional module can be tested prior to the actual final assembly with the ink housing. Defective parts are consequently rejected or repaired in good time. A just-in-time quality control eliminates the assembly of defective functional groups in the construction of the ink printing head.

The functional group produced by the novel production process has a low overall height and an advantageous base area. This makes a simple, space-saving intermediate storage in slide-magazine”-like containers possible.

In the ink printing heads produced by the novel process, there is a good heat dissipation from the jet module to the aluminium plate as a result of the precisely specified, thin adhesive film. A further advantage results from a displacement of the central holes, which have hitherto been situated on the ink container, to the aluminium plate: the functional modular group no longer has to be positioned exactly with respect to the housing since the latter only has the function of providing ink.

Suitable heat-sealing adhesive films for the above application purpose are produced on the basis of phenolic resin and nitrile rubber. They can be obtained in thicknesses of less than 30 pm, for example 25 pm, and ensure a good heat transfer. An advantage of these films is that the polymerisation of the organic material can be accelerated, in particular, by high-frequency energy.

Apart from the described assembly of ink printing 5 heads, the specified process, in which, therefore, the earlier epoxy adhesives have been replaced by thin, precisely specified heat-sealing adhesive films, can also be used in other problems encountered in practice to produce adhesive joints. In all cases an improvement in the ease of use and, consequently, the possibility of automated manufacture emerge.

Claims

1. Process for the production of an adhesive joint between at least one component, in particular an electronic component such as a semiconductor chip or the 5 like, and a metallic substrate, in particular for the assembly of ink printing heads, in which process components and metallic substrate are mutually joined as complementary parts by bonding, characterised by the use, between the complementary parts to be bonded, of an 10 adhesive film (heat-sealing adhesive film) which reacts as a result of heat.

2. Process according to Claim 1, characterised by application in the assembly of ink printing heads, in which assembly the complementary parts to be bonded are 15 an aluminium plate as metallic substrate and, as components, a printed circuit board, on the one hand, and a jet module, on the other hand.

3. Process according to Claim 1 or 2, characterised in that the metallic substrate is heated for the produc20 tion of the bonded joint.

4. Process according to Claim 3, characterised in that the metallic substrate is heated in a contact-free manner, in particular by induction.

5. Process according to Claim 2 or 3, characterised 25 in that the metallic substrate is heated in a controlled manner.

6. Process according to Claim 1 or one of Claims 2 to 4, characterised in that a heat-sealing adhesive film is used whose polymerisation is accelerated by exposure 30 to high-frequency energy.

7. Process according to Claim 1, characterised in that a heat-sealing adhesive film made of a mixture of phenolic resin and nitrile rubber is used.

8. Process according to Claim 1, characterised in 35 that, as heat-sealing adhesive film, a film of precisely specified thinness is used, in particular one having a thickness of less than 30 pm.

9. Process according to one of the preceding claims, characterised in that the metallic substrate is degreased before the application of the heat-sealing adhesive film to the complementary parts to be bonded. 5 10. Process according to one of the preceding claims, characterised in that the heat-sealing adhesive film is joined, for example by cladding with aluminium stripe, beforehand to the metallic substrate as part of an integrated manufacture.

10

11. , Process according to Claim 8, characterised in that the shape of the adhesive film is obtained by subsequent punching.---—.....— - 9

12. An adhesive bonding assembly process, substantially as described herein, with reference to, and as shown in, the accompanying drawings.

13. An arrangement comprising an electronic component, such as a 5 semiconductor chip or the like, and a metallic subst»a6e, bonded together by a process as claimed in any one of the preceding claims.