FR2771673A1 - Brazing solution placement unit control mechanism - Google Patents

Abstract

The mechanism uses a mini-stencil having a thin sheet of synthetic material or metallic sheet having orifices for dispensing the product. Two of the sheet parallel sides have brackets (3) , with other two sides being extended by flexible walls. A stretching fold separates the perforated sheet and the walls. An arrangement for using it has an arm (20) for moving the stencil along six degrees of freedom.

Description

UNIVERSAL SELECTIVE SERIGRAPUILING DEVICE
The present invention relates to an automatic or manual device dedicated to selective screen printing.

All the examples cited in this description are applied to the selective screen printing of soldering cream, glues or flux on two or three dimensional printed circuits.
on the other hand, applications to the present invention can be found in fields other than that of electronic assembly.

 Selective screen printing is necessary when obstacles are thicker than the area to be screen printed. This is the case when it is necessary to replace or add a component on a face of the card already equipped with other electronic components, it is also the case if the electronic card is inside a case or of a printed circuit molded in three dimensions.

There are selective screen printing devices on the market which are almost always based on the same operating principle as follows
- The substrate is placed on a laying device which allows the area to be screen printed to be placed horizontally.

 A combination of movements X, Y, O allows the alignment of the zone of substrate to be screen printed with the micro-stencil, these movements being generally conferred on the setting device which is mounted on a table with crossed movements, X, Y and rotation O.

 - The micro-stencil is mounted on a vertical axis which makes it possible to bring it into contact with the horizontal zone to be screen printed, as well as to separate it from this zone when the screen printing has been done.

 - Screen printing is done manually with a spatula.

 Existing devices have a number of drawbacks. First of all, it is very difficult to place the zone to be screen printed in a perfectly horizontal plane because the cards equipped can be either veiled or difficult to position and to maintain in position because of the presence and the proximity of the other components. The consequence is that the screen printing will be of poor quality if the contact between the micro-stencil and the substrate is not perfect or else an extremely tedious and long establishment of the substrate or even impossible in certain cases when the substrate is part of a subset.

 Another problem related to current devices which stems from both the operating principle and the difficulty of intimate contact between the substrate and the micro-stencil therefore results in a difficulty in automating selective screen printing.

 To overcome these problems, the same applicant proposed a first solution in patent application No. 97. 11507 which consists of a mini-stencil and its self-positioning system for the repair and / or replacement of unit components on a electronic card. This device effectively allows intimate contact between the substrate and the mini-stencil. In addition, the flaps with which the mini-stencils described are provided make it possible to avoid overflowing of products during screen printing, which is extremely interesting for a possible automation of the scraping.

 The mounting of such a device is carried out in a conventional manner, that is to say on an axis Z which can be moved vertically, and the circuit to be repaired on a table with crossed movements X and Y and rotation O. Such a positioning operation simultaneously requires action on four movements (X, Y, O, Z). However, an operator can only act on a couple of elements at a time. Therefore, the search for perfection of adjustment is long.

 - Figure 1 gives an embodiment of the prior art.

 - Figure 2 shows the device according to the invention.

 The device according to the invention allows by a single action on the stencil support, which can move in all directions of space when it is loosened, to search at once for the ideal position in X, Y, 0 , Z. The stencil holder for self-positioning makes it possible to search for the parallel planes between stencil and substrate.

 The present invention also makes it possible to further increase the access capacity of the mini-stencil. Thus, it becomes possible to screen print on extremely inaccessible areas and positioned in any way in space.

 To this end, the invention combines an articulated arm which can move in the six degrees of freedom and a tensioning and self-positioning device with a mini-stencil. The arm itself is associated with a means of displacement in vertical translation.

 According to a version with entirely manual control in FIG. 2, the device which is the subject of the present invention is provided with an articulated arm 1 which can move according to the six degrees of freedom. An operating member 5 makes it possible to mechanically or hydraulically block all of the movements. When the stencil 12 is applied to a substrate, the micro-stencil can be immobilized or removed by a single action on this operating member. This control member 5 is in the form of a screw button in Figure 2, it could be replaced by a foot control device.

Arms of this type, generally with four strands, articulated, are used in industry and more particularly in metrology as a comparator support.

 The articulated arm I is fixed on a plate 6 which can move in translation vertically relative to the support 8 itself fixed on a table 9. A dovetail device or any other linear guide may be suitable. A handle 7 articulated around an axis linked to the support 8 and bearing on another axis linked to a plate 6 makes it possible to move the stencil arm in the vertical axis.

 Therefore, it is very easy to unmold the micro stencil 12 when the manual screen printing is carried out.

 In addition, it suffices to place the doctor blade on a slide as described in FIG. 1 to automate selective screen printing.

 Figure 2 attached shows a device according to the present invention.

 In I is represented the manipulator which in the present case is with displacement and with manual blocking, this manipulator arm allows a displacement according to the six degrees of freedom of the mini-stencil and of the self-positioning system represented in 2, the doctor blade 4 translates using the slide manually.

 It goes without saying that the arm 1 as well as the slide 3 could be automatic movements. It is also understood that the manipulator arm I which is in the form of an arm can be in the form of a gantry. This device therefore makes it possible to move the stencil assembly more scrapes in any position of the space in order to carry out a screen printing there.

Claims (4)

CLAIMS.  - An articulated arm l which can move in the six degrees of freedom. This arm is equipped at one end with a tensioning and self-positioning device 2 with a mini-stencil 12.  - - Automatic or manual device dedicated to selective screen printing characterized in that it comprises  The other end of the arm 1 is integral with a slide 6 which can move in translation and vertically on a support 8 fixed on a table 9.  2 - Device according to claim 1 characterized in that a handle 7 makes it possible to lift and descend by simple pressing in one direction and in the other, the arm I associated with the stencil holder 2.  3 - Device according to claim 1 characterized in that an operating member associated with the arm I can immobilize in a single operation the micro stencil 12 when it is applied to the substrate to be screen printed.  4 - Device according to claims I to 3 characterized in that a doctor blade 4 can circulate on the mini-stencil 12.