EP2329884B1 - Method for hardening an adhesive material - Google Patents

Abstract

The method for hardening an adhesive (3'), which is arranged on a first component (1') and a second component (2') to be adhered with the first component, by application of adhesive with a radiation (20), comprises influencing a part of the radiation directed in the direction of the adhesive in such a way that the part strikes on the selected area of the adhesive. The part of the radiation is blocked or diverted. A complete application of the adhesive with the radiation is carried out with a further irradiation process. The method for hardening an adhesive (3'), which is arranged on a first component (1') and on a second component (2') to be adhered with the first component, by application of adhesive with a radiation (20), comprises influencing a part of the radiation directed in the direction of the adhesive in such a way that the part strikes on the selected area of the adhesive. The part of the radiation is blocked or diverted. The ratio of the area and/or the surface on which the radiation is not striked on the basis of blockage or diversion on the available adhesive is selected to the area and/or the surface on which the radiation is striked on the available adhesive, in such a way that the adhesive volume not stopping the radiation is slightly greater than the shrink volume of the hardened adhesive. A complete application of the adhesive with the radiation is carried out with a further irradiation process. The adhesive is applied as layer between the components to be adhered, and a flat, radiopaque mask is used as means for partial blockage of the beam, where the mask is equipped with a radiation permeable area and is positioned between the radiation source and the component to be adhered. The radiation is UV-radiation and the adhesive is UV-curable adhesive. An independent claim is included for a microfluidic system.

Description

The invention relates to a method for curing an adhesive, which is arranged on at least one first component and at least one to be bonded to the first component second component, wherein the curing is initiated by application of the adhesive with a radiation.

In many areas of technology and in particular in the field of microsystems technology, it is necessary to assemble components and functional groups by using various joining techniques. For insoluble compounds, it is common and has been proven to assemble components by gluing. Here again, in particular adhesives are used, which harden relatively quickly after exposure to radiation. However, as the adhesives cure, they undergo more or less shrinkage. This can create undefined voids on or between the parts to be bonded, for example, when the adhesive is applied between the components to be bonded and the distance between the components during the curing of the adhesive can not be adjusted automatically.
Due to the shrinkage, the adhesion of the components or the strength of the entire assembly can be unintentionally negatively affected.

The DE 198 56 333 A1 discloses, for example, an adhesive method in which two components to be bonded together are provided with an epoxy adhesive between their facing, plane-parallel surfaces, then pre-adjusted with an adjustment device relative to each other and then wetted at its edge region with a UV adhesive. Subsequently, the UV adhesive is exposed to UV radiation and cured, so that the adjustment device can release the so prefixed components again and the components can be fed to a furnace in which then takes place a curing of the epoxy adhesive.

In the DE 10 2005 058 519 A1 discloses a method for highly accurate positioning of components in the micro range. In this case, movements of the components are optically detected and automatically corrected by a movement system to break the polymer structures during the curing process of a relatively rapidly curable UV adhesive and correct by the curing of the UV adhesive conditional position deviations in time.

The invention is based on the object to provide a generic method in which the initially mentioned negative effects can be reduced. This object is achieved with the characterizing features of claim 1. Advantageous embodiments or developments of the invention can be taken from the respective subclaims.

The invention is therefore based on a method for curing an adhesive, which is arranged on at least one first component and at least one to be bonded to the first component second component, wherein the curing is initiated by application of the adhesive with a radiation.

According to the invention, it is provided that a part of the radiation directed in the direction of the adhesive is influenced such that it does not impinge on the adhesive, but at least only on a selected area of the adhesive.
This technical measure makes it possible that only a partial curing takes place in the adhesive. The acted upon by the radiation adhesive portion is first cured. During the curing process, a negative pressure arises due to the shrinkage, whereby the still liquid adhesive portion moves towards the shrinking, curing adhesive area. In this way, it is possible to generate cavities in targeted (defined) areas of the adhesive (and indeed in the areas in which the radiation could not hit these areas due to suitable influencing) and thus a desired change or control of the technical properties (For example, adhesion, strength) of the bonded assembly to achieve. By suitable influencing of the radiation, for example, it can be ensured that cavities are distributed only at uncritical locations or in an orderly manner, so that overall the assembly properties are not adversely affected. The presence of critical or uncritical places depends on the present application or the functional elements used. Uncritically, for example, be places with lower strength or tightness requirements or bodies in the area no bridging through a cavity channels are available.
The curing time of commonly used adhesives is about 10 to 20 seconds, whereby already after about 1 to 2 seconds, the adhesive thickened (gelled) so that it barely flows. Moreover, the adhesives commonly used already have only a limited flowability anyway. As a result, the resulting cavities during curing on the length dimensions, which are typically smaller than a few mm.

According to a first advantageous development of the invention, it is provided that a part of the radiation is blocked or deflected. This is a very effective and easy to implement way of influencing the radiation. For example, it is conceivable that the radiation is partially blocked by means which are introduced between the radiation source and the adhesive and are impermeable to the radiation used. But it is also quite possible to divert a portion of the radiation only. For example, a deflection of the radiation can take place in such a way that it can not strike the adhesive either at all or only at another (desired) point on the adhesive. Depending on the type of radiation used (for example, electron radiation), it is also conceivable to perform a deflection electromagnetically by means of a suitable control, which would allow an enormous flexibility in the manufacturing process. It is of course also conceivable, for example, to use light as radiation (for example laser beams) and to deflect this radiation by suitable means (for example movable mirrors). Of course, this requires appropriate adhesives, which also cure in the selected radiation.

It is very convenient that the ratio of the area or area to which the jets can not impinge on the existing adhesive due to blocking or deflection to the area or area on which the jets impinge on the existing adhesive so too Select that the adhesive volume not exposed to the rays at least slightly larger than the shrinkage volume of the curing adhesive. Due to the shrinkage of the thermosetting adhesive in the areas where the radiation can impinge on it, the still liquid adhesive in the areas where the radiation does not impinge on it, namely, tends to flow in the direction of the curing, shrinking adhesive. This leads to tensions and ultimately to the cavity-like tearing (cavitation). By choosing the ratio above, the stress in the adhesive caused by the shrinkage is reduced, since it is ensured that a minimum of liquid adhesive can flow during the partial curing process. However, it must also be taken into account that, in order to provide a required minimum adhesive force between the components as a whole, a minimum size of the area or the area is to be provided where, overall, the radiation can reach the adhesive unhindered.
Furthermore, care should be taken that as far as possible a closed system is formed in the region of the adhesive bond to be cured, ie no undesired gas or Air access is made possible, which could again lead to an uncontrolled formation of cavities.
A further advantageous embodiment of the inventive idea provides that in a further irradiation process a complete admission of the adhesive to the radiation takes place. Although the adhesion of the components to one another is primarily ensured by the areas initially irradiated in the first irradiation process (in which partial curing of the adhesive begins), further exposure of the adhesive to radiation can fully cure it, without any new cavities being created. The existing cavities are only a little larger.

If only two plane-parallel surfaces are to be glued together by the method according to the invention, the adhesive may advantageously be introduced as a layer between the components to be bonded and a flat, radiation-impermeable mask provided with radiation-transmissive regions as a means for partially blocking the radiation is positioned between the radiation source and the components to be bonded. In this way, on the one hand, a simple and comparatively flexible manufacturing structure is made possible, on the other hand, good results can be achieved with regard to a desired strength of the assemblies which are glued together.

UV radiation has proved to be particularly suitable as radiation and, correspondingly, as adhesive, a UV-curing adhesive. UV adhesives are one-component (easily processable), solvent-free and very quickly curable. Preferably, acrylate-based adhesives (for example Vitralit® 5140 or Vitralit® UV 4024) or cyanoacrylate-based (for example Loctite® 4305) are used.

The effect that it is possible to generate cavities in defined areas in the above-described method also makes it possible to use the method according to the invention for the targeted structuring of a microfluidic system. This is conceivable, for example, for cases where fluidic channel systems are to be capped or closed by gluing. For example, additional microfluidic channels, ventilation channels and capillaries of a few micrometers in the adhesive can be produced with a very high surface quality that would be difficult to achieve by other structuring methods (for example because of the small depth or because of the surface accuracy).

Due to the effect that the cavities formed in the described method can mechanically result in lower adhesion of the components bonded to one another, the method according to the invention can even be used for the targeted production of overpressure nominal separation points in a microfluidic system.

The method can therefore also be used to produce a microfluidic system comprising at least one component with at least one channel. In this case, at least one channel of the microfluidic system is at least partially limited by a radiation-curing adhesive. The channel can in this way partially have a very high surface quality.

Furthermore, a microfluidic system, comprising at least two components glued together by an adhesive, within which at least one channel or a collecting space for a fluid is formed, wherein at least one cavity in the adhesive, can be produced. The at least one cavity is selected in its position such that in the region of the cavity when a certain fluid pressure is exceeded, the components bonded together are separated. As a result of this measure, a microfluidic system with positive pressure separating points is provided in a simple manner.

Fig. 1

eine äußerst prinziphafte Schnittdarstellung zur Erläuterung eines ersten Ausführungsbeispiels des erfindungsgemäßen Verfahrens,

Fig. 2

eine äußerst prinziphafte Schnittdarstellung zur Erläuterung eines optionalen zweiten Verfahrensschritts vom ersten Ausführungsbeispiel des erfindungsgemäßen Verfahrens,

Fig. 3

eine äußerst prinziphafte Darstellung in einer Draufsicht zur Erläuterung eines zweiten Ausführungsbeispiels des erfindungsgemäßen Verfahrens,

Fig. 4

eine äußerst prinziphafte Schnittdarstellung zur Erläuterung einer erfindungsgemäßen Verwendung des erfindungsgemäßen Verfahrens und

Fig. 5

eine äußerst prinziphafte Schnittdarstellung zur Erläuterung eines weiteren Ausführungsbeispiels des erfindungsgemäßen Verfahrens.

Further advantages and embodiments of the method according to the invention will be apparent from preferred embodiments, which will be explained in more detail with the aid of the accompanying figures. Mean

Fig. 1

an extremely schematic sectional view for explaining a first embodiment of the method according to the invention,

Fig. 2

an extremely schematic sectional view for explaining an optional second method step of the first embodiment of the method according to the invention,

Fig. 3

an extremely schematic representation in a plan view for explaining a second embodiment of the method according to the invention,

Fig. 4

an extremely schematic sectional view for explaining an inventive use of the method and

Fig. 5

an extremely schematic sectional view for explaining a further embodiment of the method according to the invention.

Identical parts are provided with the same reference numerals. First, on the Fig. 1 and 2 Referenced. Therein, a first planar component 1 (for example of plastic) and a second planar component 2 can be seen from a section of a microfluidic assembly (not shown further). Between the components 1 and 2, a radiation-curing adhesive 3 is introduced areally. A radiation source, not shown, emits beams 4 in the direction of the adhesive 3. Between the radiation source and the adhesive 3, a cover mask 5 is positioned, which has radiation-impermeable regions 50 and radiation-permeable regions 51. The radiation 4 passing through the radiation-transmissive regions 51 passes through the likewise radiation-transmissive component 2 (for example glass) onto the adhesive 3 underneath. This begins to harden in these regions, whereby it is subject to shrinkage in certain dimensions, depending on the type of adhesive used and the radiation used. In the specifically illustrated embodiment, a UV-curing adhesive is used in combination with a UV radiation source. Most UV adhesives have a shrinkage during curing of about 2-10%. As a result of the shrinkage, the still liquid adhesive 3 located below the radiopaque regions 50 endeavors to flow in the direction of the irradiated regions of the adhesive 3. As a result, cavities 6 form below the radiopaque regions 50 of the mask 5. The mask 5 is selectively positioned or formed so that the formation of the cavities 6 takes place only at non-critical points, that is, for example, at those points where a reduced by the cavities 6 adhesive force can be accepted. The microfluidic assembly shown has correspondingly small dimensions. Thus, the thickness of the components 1 and 2 is about 0.5 -1 mm and the layer thickness of the adhesive 3 is about 200-300 microns, wherein the distance between the mask 5 and the adhesive 3 is to be chosen as low as possible, so that caused by scattered radiation disadvantages ( Edge effects) can be avoided as much as possible. The distance is therefore approximately 0.5-1mm, wherein the mask 5 may well rest on the second component 2.

In Fig. 2 now a second optional process step is shown. It can be seen that in this case the mask 5 has been removed from the beam path, the original position of which is indicated only by dashed lines. It is now possible for all the beams 4 to impinge unhindered on the adhesive 3, whereby a complete curing of the adhesive 3 takes place. As a result of the complete curing of the adhesive 3, the cavities 6 essentially do not change their position. There are also no new cavities. The cavities 6 only slightly increase in size (compare 6 ').

In the Fig. 3 In a top view, a microfluidic assembly consisting of a first component 7 and a second component 9 resting thereon is also shown. The first component 7 may in turn be made of plastic, for example, and the second component 9 of UV-transparent glass. The first component 7 has a circular opening 8, which is to ensure, for example, the fluidic and fluid-tight access of a channel system not shown to a pressure sensor, also not shown. For a specific influencing of a bond, an annular covering mask 10 with an inner diameter 100 located at a concentric distance from the opening 8 is placed on the second component 9. The cover mask 10 is made of a UV-impermeable material, for example chromium or aluminum. Between the first component 7 and the second component 9, a UV-curing adhesive for bonding the components 7 and 9 is introduced in the region of the cover mask 10, which is not shown in greater detail in this illustration. Specifically, the adhesive is applied so that, radially seen, an area wetted by adhesive 11 results, which in turn subdivides into an area 12 covered by radiation by the covering mask 10 and an area 13 accessible for the UV radiation. If UV radiation is now emitted in the direction of the adhesive, it is blocked in the area 12 by the mask 10 and can impinge unhindered on the adhesive only in the area 13. As a result, curing of the adhesive with concomitant shrinkage in this area takes place, as already described, which leads to liquid adhesive from area 12 flowing into area 13. However, these cavities 14 are not located in the critical area directly at the opening 8 (in this area should be a reliable bond and tightness), but radially away from it. The surface of the cover mask 10 is selected so that under this sufficient liquid adhesive is absorbed, which can flow into the region 13 upon curing of the irradiated adhesive and thus in the entire region 13 is a cured, void-free adhesive layer.

In Fig. 4 is shown how the inventive method can be used in a special way. Thus, in turn, a microfluidic component 15 with a plurality of capillary channels 16 can be seen in a plan view. On the component 15, a not-shown component for capping the capillary channels 16 is also provided. With the aid of the method according to the invention, it is now possible to form an additional (self-contained) capillary channel 16 ', which partially consists of hardened adhesive 19 and has a very high surface quality. For this purpose, at the desired location of the component 15 (and indeed in the crossing region of two existing Kapillarkanälen) liquid adhesive 17 is introduced, then the component 15 closed by the mentioned, not shown component for capping and then at this point a Abdeckmaske 18 in such Size, position and shape applied that the adhesive 17 can not be hit in the center of the crossing region of the radiation, but at least partially at the edge of the crossing region. During the curing of the adhesive 17 this will shrink in the manner already described (19) and liquid adhesive 17 by pulling so that the capillary channel 16 'is formed.

Finally, in Fig. 5 one with the in the Fig. 1 and 2 shown comparable view, with which a further embodiment of the method according to the invention is to be explained. Here too, a first microfluidic component 1 'can be seen on which a second microfluidic component 2' (permeable to the radiation used in the example) is applied. Between the components 1 'and 2' in turn an adhesive 3 'is provided, which cures by the radiation used. Furthermore, rays 20, 20 '(electron beams) can be seen, with which the adhesive 3 is acted upon. In contrast to the first embodiment according to Fig. 1 In this case, targeted blocking of the rays through a mask does not take place, but partial targeted diversion of the rays 20 'takes place by suitable means in each case (for example controllable electromagnets, not shown in greater detail). It can be seen that a range 21 of increased radiation intensity is produced by the deflected beams 20 '(which may well be desirable and advantageous for certain applications) and a region 22 in which no rays impinge on the adhesive 3'. Due to the shrinkage of the adhesive 3 'during its curing, in turn, a cavity 6 is formed in the region 22 in a controlled manner. Since the deflection of the beams 20 'can be controlled, this can be flexibly adapted to the respective application.

LIST OF REFERENCE NUMBERS

1,1 '

first component

2,2 '

second component

3,3 '

adhesive

4

radiation

5

mask

50

radiopaque areas

51

Radiation-permeable areas

6, 6 '

cavities

7

first component

8th

Opening in the first component

9

second component

10

circular cover mask

100

Inner diameter of the cover

11

area wetted with adhesive

12

Covered by mask area

13

radiation accessible area

14

cavities

15

microfluidic component

16

capillary

17

liquid adhesive

18

mask

19

cured adhesive

20, 20 '

radiation

21

Range of increased radiation intensity

22

Area where no radiation hits the glue

Claims (10)

1. Method of curing an adhesive (3, 3') which is provided on at least one first component (1, 7, 15) and on at least one second component (2, 9) that is to be adhesively bonded to the first component (1, 7, 15), the curing being initiated by impacting the adhesive (3, 3') with radiation (4, 20, 20'), and some of the radiation (4, 20) directed towards the adhesive (3, 3') being influenced such that areas (12, 22, 50) are formed where the radiation (4, 20) does not impact the adhesive (3, 3'), but at least impacts only a selected area (13, 21, 51) of the adhesive (3, 3'), characterised in that in the areas (12, 22, 50) where the radiation (4, 20) does not impact the adhesive (3, 3') cavities (6, 14) are produced in the adhesive (3, 3').
2. Method according to claim 1, characterised in that some of the radiation (4) is blocked.
3. Method according to claim 1, characterised in that some of the radiation (20) is deflected.
4. Method according to at least one of the preceding claims, characterised in that in a further radiation process all the adhesive (3, 3') is impacted with the radiation (4, 20).
5. Method according to at least one of the preceding claims, characterised in that the adhesive (3, 3') is introduced as a layer between the components (1, 2 or 7, 9) that are to be bonded and a flat, radiation-impervious mask (9, 10) is used as a means for partially blocking the radiation (4), which is provided with radiation-pervious areas (51, 100) and is positioned between the radiation source and the components (1, 2 or 7, 9) that are to be bonded.
6. Method according to claim 5, characterised in that the mask (10) is circular.
7. Method according to claim 6, characterised in that the adhesive is introduced between a first component (7) and a second component (9), the first component (7) having a circular opening (8) and the mask (10) being placed on the second component (9) at a concentric spacing from the opening (8).
8. Method according to at least one of the preceding claims, characterised in that the adhesive (17) is introduced between a microfluidic component (15) having a plurality of capillary channels (16) and a component for providing a cover in the area of intersection of two capillary channels (16), and a mask (18) is provided, the size, position and shape of which are such that the adhesive (17) cannot be impacted by the radiation in the centre of the area of intersection, but can be impacted at least partially at the edge of the area of intersection, such that an additional capillary channel (16') is formed during the curing of the adhesive (17).
9. Method according to at least one of the preceding claims 3 to 8, characterised in that the deflection of the radiation (20') produces a region (21) of increased radiation intensity.
10. Method according to at least one of the preceding claims 3 to 9, characterised in that the deflection of the radiation (20') is controllable.

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