DE4434917C1 - Selective application of adhesive to a substrate surface - Google Patents

Abstract

The adhesive is applied to the total substrate area and then the laser light is applied to selected regions to connect the adhesive to the substrate surface. Excess adhesive or adhesive components are then removed in the non-selected areas. The adhesive is pref. applied in powder form and excess adhesive is pref. sucked away.

Description

When automatically populating printed circuit boards with SMD Modules for surface mounting (SMD = Surface Mounted Devices) are indicated by a in a positioning unit arranged dosing device first glue drops on which the SMD modules are then placed. The adhesive then hardens under the influence of temperature or UV radiation. The SMD modules are then in the correct position so firmly on the circuit board that the electrical connection in the wave pool, by reflow soldering or can be produced by soldering in the vapor phase. The dosing device used for applying the adhesive lines consist essentially of a resilient Bracket arranged and pressurized with compressed air Adhesive cartridge, one inserted into the adhesive cartridge set dosing nozzle and one assigned to the dosing nozzle Spacers. To apply a drop of adhesive this in the positioning unit of the SMD placement machine arranged metering device lowered until the distance Hal ter sits on the circuit board, thereby causing the gentle impact due to compression of the adhesive cartridge is caught. From yourself in this lowered position dosing nozzle located just above the circuit board then pressurize the adhesive cartridge with compressed air Adhesive drops pressed onto the circuit board, the dosed amount of adhesive from the dosing time, from pressure, with which is applied to the adhesive cartridge by the nozzle geo metry and the viscosity of the adhesive depends. The Dyna Mixing viscosity in turn depends on the temperature of the Adhesive. Can increase the dosing accuracy therefore the dosing nozzle also has a cooling and / or heating device device for temperature stabilization of the passed Adhesive can be assigned (cf. EP-A-0 282 748).  

DE-A-21 29 926 describes a process for the production of Markers known, in which fine particles on a Applied object and ent with the help of a laser beam speaking of the desired marking with the surface of the Object to be glued. Then the Particles that did not adhere to the surface of the object ten away. For the particles used for the marking can be mixtures of a pigment and a thermopla material to form mixtures of a pigment and a Resin, colored high molecular materials or Me trade tall powder.

From US-Z IBM Technical Disclosure Bulletin, Vol. 15, No. February 9, 1973, page 2855 is a selective method Metallization of ceramic substrates is known, in which too next a metal-containing thermoplastic powder on the green ceramic substrate is applied. In the area of the conductor tracks then become the powder by action of a laser beam with the surface of the green kera Miksubstrats connected. After removing the excess The green Kera then becomes non-adhering powder Miksubstrat fired, the thermoplastic material evaporates and the metal particles through together tern continuous and well adhering to the substrate Lei form trains.

The invention specified in claims 1 and 2 is Problem based, a method for locally defined Auf apply small amounts of adhesive to a substrate create that in a short time and without handling problems can be carried out.

The invention is based on the finding that selective irradiation of an adhesive or an adhesive  component with an energy beam adhering the irradiation th material on the surface of a substrate in a lo cal defined area and in a precisely dosed amount can be effected. The irradiated material then forms neither directly a usable glue or it can activated by a physical or chemical process will. The irradiated material can also by large areas Add one or more other components in egg a usable adhesive. The over shot amount of rea not with the irradiated material The additional components can then be removed.

Advantageous embodiments of the invention are in the sub claims specified.

According to claim 3, the adhesive or the adhesive compo nente in a simple manner in powder form on the substrate to be brought. The powder then becomes selective in the way irradiated that the powder granules at the irradiated point connect with each other and possibly react with each other and the associated powder grains on the surface of the Adhere substrate. The excess, non-stick powder can then be sucked off according to claim 4 in a simple manner the.

According to claim 5, the adhesive or the adhesive compo nente also applied in liquid form to the substrate will. According to claim 6, the liquid adhesive or the liquid adhesive component through the selective loading radiation locally in a viscous or solid state are transferred, the adhesive or the adhesive com component adheres to the substrate in this state and wherein there may also be a chemical change can. In the last step, the excess liquid becomes  removed. If this is not adhering to the substrate, then removal is particularly easy. Otherwise a Ver drive like B. Dissolve with a solvent selected the one that removes the excess liquid without the attack substances treated by radiation.

Finally, according to claims 7 and 8, it is also possible the adhesive or the adhesive component in the form of a Ge quantities or in the form of a dispersion on the substrate bring.

The embodiment according to claim 9 enables the economy use of lasers for selective irradiation. Becomes use a deflectable laser beam according to claim 10 det, so the selective radiation in the selected Areas very quickly and if necessary also program-controlled be made.

The following is an embodiment of the invention hand of the drawing explained in more detail.

Show it

Fig. 1, the application of an adhesive in powder form to a substrate,

Fig. 2, the selective irradiation of the FIG. 1 adhesive applied with a laser beam,

Fig. 3 after the removal of the excess adhesive fes remaining on the substrate and adhesive

Fig. 4 is a system for the selective irradiation of the adhesive shown in Fig. 2.

Figs. 1 to 3 show in a very simplified representation of various methods schemati shear stages in the selec tive applying adhesive to a substrate.

According to FIG. 1, a powdery adhesive K of uniform thickness is first distributed over the entire surface of the upper surface F of a substrate S.

The adhesive applied to the surface F is then exposed to a laser beam L in a selected area according to FIG. 2. The individual grains of adhesive K then bond to one another at the irradiated point. In addition, the interconnected grains of the adhesive K adhere to the surface of the substrate S due to the action of the laser beam L.

According to FIG. 3, the excess powdery adhesive K is removed after the irradiation, for example by suction. The powdery adhesive K removed in this way can later be easily reused.

On the upper surface F of the substrate S, in the selected area designated B in FIG. 3, the grains of the adhesive K bonded to one another and to the surface of the substrate S remain in a precisely metered amount. This amount depends on the thickness of the powdery adhesive K applied in the first step according to FIG. 1. The adhesive K remaining on the surface F of the substrate S is also defined very precisely locally by the action of the laser beam L locally limited according to FIG. 2 on the selected region B.

Fig. 4 shows a highly simplified schematic presen- tation a system for selective irradiation of the powdered adhesive K applied to the substrate S. The powder grains of the adhesive K are indicated by small dots.

The system shown comprises a laser La which generates a laser beam L, in the beam path of which a photo shutter Fv, a first rotatable deflecting mirror Asx of a deflecting lens Ao, a second rotatable deflecting mirror Asy of the deflecting lens Ao and an objective O are arranged, which are the laser beam L focused on the surface of the substrate S. The position of the substrate S is defined in relation to a flat, Cartesian x, y coordinate system. Accordingly, the first deflecting mirror Asx of the deflecting system Ao has the task of deflecting the laser beam L in the horizontal direction, which is indicated in FIG. 4 by a double arrow x '. The second deflecting mirror Asy of the deflecting technique Ao has the task of deflecting the laser beam L in the direction y perpendicular to the x-direction, which is indicated in FIG. 4 by a double arrow y '.

The deflection mirrors Asx and Asy are controlled according to the selected areas B on the substrate S to be coated with adhesive K (cf. FIG. 3) by a microcomputer Mc, to which an input E is assigned. The lines for the control of the deflection mirrors Asx and Asy are labeled Lex and Ley. The microcomputer Mc also controls the photo shutter Fv, which is shown by a corresponding line Le.

For the selective transfer of the adhesive K to the substrate S, the completely applied powder layer is coated by the laser beam L in accordance with the configuration of the selected areas B (cf. FIG. 3) entered into the microcomputer Mc via the input E. Then only the excess adhesive K which does not adhere to the substrate S then has to be removed.

The above-described with reference to FIGS. 1 to 4, he assisted application of adhesive to selected areas of a substrate can be used in a wide variety of applications. For example, in the automatic assembly of printed circuit boards with SMD components, the application of adhesive drops to the printed circuit boards described at the beginning can be replaced with the aid of a metering device by means of the laser-assisted application of the adhesive, which is quicker and easier to carry out. Other possible applications for laser-assisted application of adhesive include microsystem technology, built-in technology and the manufacture of electronic assemblies.

Claims (10)

1. Method for applying adhesive (K) to selected areas (B) on at least one surface (F) of a substrate (S) with the following steps:

• a) applying the adhesive (K) to the entire surface (F) of the substrate (S) in which the selected areas (B) lie;
• b) selective irradiation of the adhesive (K) in the selected areas (B) with an energy beam for connecting the irradiated adhesive (K) to the surface of the substrate (S);
• c) removing the excess adhesive (K) or the excess adhesive component in the unselected areas of the substrate (S).

2. Method for applying adhesive (K) to selected areas (B) on at least one surface (F) of a substrate (S) with the following steps:

• a) applying an adhesive component to the entire surface (F) of the substrate (S) in which the selected areas (B) lie;
• b) selective irradiation of the adhesive component in the selected areas (B) with an energy beam for binding the irradiated adhesive component to the surface of the substrate (S);
• c) removing the excess adhesive component in the unselected areas of the substrate (S);
• d) converting the irradiated adhesive component into an adhesive by adding one or more other components.

3. The method according to claim 1 or 2, characterized records that in step (a) the adhesive (K) or the Adhesive component is applied in powder form. 4. The method according to claim 3, characterized in net that the excess adhesive (K) or the over shot adhesive component after selective irradiation is suctioned off. 5. The method according to claim 1 or 2, characterized records that in step (a) the adhesive (K) or the Adhesive component is applied in liquid form. 6. The method according to claim 5, characterized in net that the adhesive (K) or the adhesive component in selective irradiation in a viscous or fe most state is transferred. 7. The method according to claim 1 or 2, characterized records that in step (a) the adhesive (K) or the Adhesive component is applied in the form of a mixture. 8. The method according to claim 1 or 2, characterized records that in step (a) the adhesive (K) or the Adhesive component applied in the form of a dispersion becomes. 9. The method according to any one of claims 1 to 8, characterized characterized in that in step (b) as an energy beam a laser beam (L) is used. 10. The method according to claim 9, characterized records that a deflectable laser beam (L) is used becomes.