DE102008003062A1 - Plastic microstructured components material-fit connection method, involves increasing ultrasonic power in ramp up to power level, fusing joining parts at contacts and connecting joining parts with each other in material-fit manner - Google Patents

Abstract

The method involves placing a joining part (1) and an unstructured joining part (2) on top of each other under formation of dotted or lined contacts. The parts are subjected to contact force and ultrasonic power, where ultrasonic energy is focused on the contacts. The ultrasonic power in a ramp is increased up to a power level. The parts plastically deform together at the contacts. The ultrasonic power in another ramp is increased up to another power level above the former power level. The parts are fused at the contacts and connected with each other in a material-fit manner.

Description

The The present invention relates to a method for material bonding of microstructured plastic components by means of ultrasound according to the first Claim.

The cohesive Connecting plastic components by means of ultrasound, the like called ultrasonic welding, is an introduced Method. The z. B. a piezoelectric actuator generated mechanical Vibration over a sonotrode passed into the parts to be connected. There are structures here on one of the parts to be joined on the other joining part and form a contact point. About the structure, the so-called Energy directors, while the vibration energy is focused and the two parts to be joined are melted locally at the contact point. It happens to an uncontrolled flow of the molten material. For use in microsystems technology is the uncontrolled flow the melt problematic because the flow paths of the order of magnitude the structural dimensions are regularly and significantly problems and functional failures arise.

Cheng, Truckenmüller, Ahrens and Rogge "Development and preparation of a chemically inert micropump ", Scientific Reports, FZKA 7125, 2005 discloses a method in the corresponding additional Collection structures for provided melting components in the unstructured joining part are. These structures are in a separate manufacturing step into the parts to be joined worked. Besides the need to structure both parts, is a precise positioning of the two joining partners to each other before the welding step essential so that the structures can catch the melt. This means besides the additional Effort through the structuring itself, also an additional Error source, due to inaccurate positioning of the micro-structured joining partner to each other.

outgoing It is the object of the invention to provide a method the ones listed Disadvantages and limitations avoids. In particular, the melt flow should be controllable and the production of corresponding catchment structures without separate process step or structuring of the components, the can absorb accumulating melt, allows become.

Is solved the object by a method having the features according to claim 1. The dependent claims describe advantageous embodiments of the invention.

to solution The object is a method for cohesive bonding of microstructured Components made of plastic proposed by means of ultrasound, wherein the process step for generating the actual material bond a process step is preceded, in which an energy directors by plastic deformation a cavity in the unstructured joining partner generated.

One essential thought of the procedure involves the context that in a first method step by the contact pressure and the ultrasound energy first a plastic deformation at the contact point in the unstructured joining partner is produced. That of the energy directors in this process step deepening takes place in a later process step, the welding, the resulting melt on.

to execution the method according to the invention become the at least two parts to be joined put on each other. At least one of the two joining partners is due to the presence of an energy directors (ERG) characterized. The ERG forms between the joining partners punctate or linear Contact points. Both joining partners are subjected to a contact force and an ultrasonic power, wherein the ultrasonic power up to the value of the lower (first) Performance levels increased becomes. Achieving this level of performance is a shutdown criterion for the Ultrasonic power and the contact pressure. This will be the material the joining partner plastically deformable and the ERG forms a hollow in the unstructured Joining partners.

Of the subsequent process step for generating the actual material bond Optionally, immediately following the above Process step or at any time interval performed this become. Both joining partners are applied with a contact force and an ultrasonic power, whereby the ultrasonic power up to the value of the upper (second) Performance levels increased becomes. Achieving this level is a shutdown criterion for the Ultrasonic power and the contact pressure and between two joining partners becomes a cohesive one Connected. The resulting melt is from the cavity recorded and the melt flow is thus controllable.

The performance levels of the method have complex dependencies on a variety of process parameters, such as. B. from the material of the joint partners, from the geometry of the contact areas and the microstructuring and from the sound. The determination of the performance levels is therefore preferably empirically based on experience, more preferably in the context of preliminary tests on a test setup which corresponds to that of the aforementioned method for materially joining microstructured components. Components and loading device of the preliminary tests correspond exactly to those of the actual connection method, which advantageously geometrical or material-specific influences of the joint partners involved are reduced.

The Determination of the upper performance level is achieved by a ramped increase the ultrasound power in the experimental setup, until a material deadline between the joining partners is present, thereby no further increase in the Fügeflä in the kitchen Performance more possible is and is a performance entry plateau, the so-called saturation level established.

The first (lower) power level is due to the ultrasonic power determined, in which a cohesive Connection of joining partners just does not occur, but a plastic deformation of the joining partner to create a preferred as possible huge cavity takes place. Empiric leaves only by an iterative approach to the performance level determine, preferably over a gradual increase in ultrasound power to the point in which a plastic deformation of the linear contacts occurs, but the parts do not yet connect cohesively. The entry the plastic deformation is preferably detectable via a displacement measurement, the entry of cohesive Connection only by lifting the upper joint partner. Preferably, the contact areas are after each step of the interaction, d. H. separated and checked after each performance level. Experience has shown the first, d. H. the lower performance level at 20 to 90% of the second, upper performance levels. Preferably, the lower performance level at 20 to 50% of the upper performance level.

As well is by preliminary tests, the contact force of the joining partners optimized against each other. It is preferably to be set so that through them the registered Ultrasonic power at the upper power level, but preferably in each adjustable power stage, a coupling of the mechanical vibrations in the joining partners and thus advantageously a concentration of the registered Ultrasonic line in the contact areas for the desired plastic deformation or the coincidence allows becomes. Preferably, the contact pressure in each power level is so kept as low as possible, preferably by testing with the registered ultrasound power is increased synchronously.

The Invention is with an embodiment closer to the figures explained.

1 . 3 and 4 shows a schematic representation of the joining partners in different stages of cohesive joining process

2 shows the time course of the ultrasonic power during the implementation of the method according to the invention

1 is a schematic representation of two parts to be joined 1 and 2 , where a joining part 1 with an energy director 3 is provided. After putting the two parts together 1 and 2 and the application of a pressing force, the ultrasonic power in a first step 4 until reaching the lower performance level 5 , as in 2 shown, increased. For joining parts 1 and 2 from z. As polymethyl methacrylate (PMMA) are preferred values for the lower performance level 5 in a range between 0.2 to 0.9 times the value of the upper performance level 6 , Particularly preferred values for the lower performance level 5 when PMMA is used, the range is between 0.25 and 0.5 times the value of the upper power level 6 , With reaching the lower performance level 5 The ultrasound is decoupled and the parts to be joined 1 and 2 be relieved. After this first process step 4 arises in the unstructured joining part 2 a cavity 7 , as in 3 is shown.

Subsequently or at any time interval to this first process step 4 , becomes a second process step 8th carried out by applying the joining parts 1 and 2 with a contact force, the ultrasonic power to reach the upper power level 6 is increased. With reaching the upper performance level 6 become the joining parts 1 and 2 relieved and the ultrasound is decoupled. After this second process step 8th creates a cohesive connection 9 between the parts to be joined 1 and 2 , as in 4 is shown.

1

Joining part with Energy director

2

unstructured adherend

3

Energy director

4

first step

5

lower (first) level of performance

6

upper (second) level of performance

7

Cavity in the unstructured adherend

8th

second step

9

Area the cohesive connection

Claims (4)

Method for integrally bonding microstructured components made of plastic by means of ultrasound with the following method steps: a) placing at least two parts to be joined to form point or linear contacts, wherein at least one of the two parts to be joined has a microstructure, b) loading of the parts to be joined with a contact pressure and an ultrasonic power, wherein an ultrasonic energy is focused on the contacts, and wherein the ultrasonic power is increased in a first ramp up to a first power level, whereby the two parts to be joined on the contacts plastically deform each other, and then the ultrasonic power in a second Ramp is increased to a second power level above the first power level, whereby the two parts melt on the contacts and connect to each other cohesively. The method of claim 1, wherein the two ramps not be executed in immediate succession. The method of claim 1, comprising a preliminary test for determining the second level of performance on a test set-up and two parts according to claim 1, comprising a ramped increase the ultrasonic power up to a saturation level at which no further increase more possible is, where the saturation level corresponds to the second level of performance. The method of claim 1, comprising a preliminary test on a test set-up and two parts according to claim 1, comprising one gradual increase of the ultrasonic power up to a plastic deformation the point or line Contacts has occurred, whereby the parts do not connect materially and checking for plastic deformation after each step.