DE20209385U1 - template - Google Patents

Description

Munich ■ Hamburg ■ Dusseldorf New York

Patent attorneys

Dr. Walter Maiwald (Munich) Dr. Volker Hamm (Hamburg) Dr. Stefan Michalski (Düsseldorf) Dr. Regina Neuefeind (Munich) Dipl.-Ing. Udo Preuss (Munich) Dipl.-Ing. Korbinian Kopf, MA. (Munich) Dr. Norbert Hansen (Munich)

Lawyer

Stephan N. Schneller (Munich)

In cooperation with: Maiwald Inc., New York Dipl.-Ing. Korbinian Kopf, M.A. U.S. Patent Agent

Dr. Schmidt-Felzmann & Kozianka Attorneys at Law (Hamburg)

Parr ■ Dive ■

Leutheusser-Schnarrenberger Attorneys at Law (Munich ■ Starnberg)

Reference number Our reference

New registration L 7228 / UP

LTC LASER SERVICES GMBH

Munich, July 8, 2002

LTC LASER SERVICES GMBH
Meisenweg 16, 75331 Engelsbrand

template

Technical area

The present invention relates to a stencil to be clamped in a clamping frame for applying a solder paste to contact points of a circuit board or for applying a conductive adhesive to a circuit board.

Nowadays, circuit boards are often assembled using the so-called SMD (surface mounted devices) design, which means that the electrical components are located with both their body and their connections on the same side of the circuit board.
Attachment and possibly also the electrical connection is then done by soldering,

UP:ps

PO Box 330523 · 80065 Munich · Elisenhof ■ Elisenstrasse 3 ■ 80335 Munich

Tel. +49 (0)89 74 72 660 ■ Fax +49 (0)89 77 64 24 ■ http://www.maiwald.de ■ info@maiwald.de

Managing Director: Dr. WdJT«tMiaM/ald«T5t VoTteiHQmrm**Dr.^efan*[Jfiohjal«k;*t5r. Reginji Neuefeind · HRB No. 111307

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especially reflow or wave soldering. For this SMD design in particular, contact points (SMD pads) must be coated with solder paste, which is often done using a screen printing process. Stencils are often used to apply the solder paste to the contact points or a conductive adhesive, which have corresponding patterns in a working area of the flat stencil. The stencils provided, which are made of metal in particular, are used to apply these patterns.

In principle, a distinction is made between glued-in stencils and quick-clamping stencils that can be clamped in a quick-clamping frame. In the present case, the invention concerns stencils that can be clamped in a quick-clamping frame. Such stencils are adapted to be gripped and clamped by suitable holding means of a clamping frame at least on two opposite edge areas. In particular, there is a row of holes, openings or slots on at least two opposite edge areas of the stencil, into which the corresponding holding means of the clamping device or clamping frame fit. However, all four edge areas of such a stencil are often gripped and clamped and accordingly have rows of holes on all four edge areas of the stencil. Clamping frames and stencils of the type mentioned are known in particular from EP 0 790 892 B1 or WO 93/25061.

Stencils of the type in question here are, as already mentioned, made in particular of metal, preferably stainless steel, and have etched, milled or laser-cut patterns for solder or conductive paste printing. They must be able to be hung very precisely and reproducibly in the clamping frame, and for the reproducibility and accuracy of applying the patterns to a circuit board, no warping or twisting may occur when the stencil is clamped. Accordingly, the above-mentioned WO 93/25061 highlights the fact that the edge areas are flexible as an essential technical feature.

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The stencils in question here are often very thin. The thickness or strength of a stencil is between 0.05 mm and 0.5 mm, especially 0.1 mm to 0.2 mm, at least in the edge area. This means that the edges and especially the respective corners are extremely sharp and can easily lead to injuries when handling the stencils. This problem has not yet been solved.

Description of the invention

The technical problem underlying the invention is to provide a template intended for clamping in a clamping device which poses a lower risk of injury to an operator.

This technical problem is solved by a stencil which is designed on at least two opposing stencil edge regions for gripping and clamping the stencil in a clamping frame, wherein at least one stencil edge region has a bent edge so that the outer edge of the stencil edge region is rounded.

The invention is based on the idea of specially designing at least that stencil edge area in such a way that there is no or at least a reduced risk of injury from this area, which has proven to be a risk of injury when handling the stencil. Stencils of the type mentioned are often stored in hanging file-like devices in which an operator can at least come into contact with the upward-facing edge or the edge, which can easily lead to cuts due to the thinness of the stencils. By now for the first time with such a stencil, especially made of metal, the free edge

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is bent over, the edge, which is actually sharp, is rounded off over the length of the stencil edge area, and is therefore less dangerous. Surprisingly, it has been found that, despite the bending of the edge, on the one hand the stencil can still be inserted into the known clamping frames intended for this purpose, and on the other hand, it has surprisingly been shown that, despite the stiffening and reinforcement of the stencil in the edge area, there is no increased risk of twisting or warping when clamped on two or four sides. At the same time, bending the edge does not require an additional protective element, which would increase production costs considerably. In the present case, the production costs for a stencil only increase insignificantly. However, these slightly higher production costs for the stencils are acceptable in view of the greatly reduced risk of injury from the otherwise extremely sharp edges of a stencil with such low thicknesses. It has also been shown that the risk of damage to the stencil during handling is reduced.

As already mentioned, a metal stencil according to the invention is designed with two or even four edge areas for gripping and clamping the stencil in the clamping frame. This means that a metal stencil according to the invention with a bent edge can be used in particular in a clamping device according to WO 93/25061 as well as EP 0 790 892 B1. It should also be noted that clamping devices according to the latter publication are also sold under the brand "Quattro-Flex®".

Preferably, stencils according to the invention for gripping and clamping the stencil in the clamping frame have a row of openings in the respective stencil edge areas for receiving suitable hooking devices of the clamping frame. These openings can in particular be round or elongated holes. The shape of the openings then corresponds to that which is known in particular from the aforementioned publications.

f « · · t · t t

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In a preferred embodiment of a stencil according to the invention, at least those stencil edge areas that are designed to grip and clamp the stencil in the clamping frame are rounded off by bending the respective associated edge. These stencil edge areas are gripped by an operator more frequently than the other stencil edge areas, so that there is an increased risk of injury from these. Preferably, however, all stencil edge areas are provided with the rounded edges.

A reduced risk of injury is achieved if the bent free edges are bent by more than 100-120°, but preferably the free edges are placed almost to the top or bottom of the stencil, i.e. bent by up to 180°.

Stencils according to the invention have an outer radius of 0.1 mm or more, particularly on the bent free edge. The outer radius is preferably larger, but it should be chosen so that it is still possible to fit into the existing clamping frame. Accordingly, the outer radius must not be chosen to be too large.

A particularly preferred embodiment of a stencil according to the invention has a bead on the bent free edges so that there is a certain thickening there, but behind this the free edge and the metal stencil almost touch each other again. This achieves a particularly good reduction in the risk of injury, but at the same time the thickening reducing the risk of injury is limited to a small part of the edge area.

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In particular, the invention is suitable for (metal) stencils with a thickness at the bent edge between a minimum of 0.1 mm and a maximum of 1.0 mm. This means that before bending, the edge area has a thickness of 0.05 mm - 0.5 mm.

Finally, it should be noted that the term "bending" also includes "flanging" and similar deformation processes.

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Short description of the drawings

For further explanation and better understanding, several embodiments of the invention are described and explained in more detail below with reference to the accompanying drawings. It shows:

Fig. 1 is a plan view of a metal template according to the invention, which is

four edge areas for gripping and clamping in a clamping frame,

Fig. 2 is a partial cross-sectional view of an edge region with a bent edge,

Fig. 3 shows another embodiment of a bent edge of a

inventive template,

Fig. 4 shows yet another embodiment of a bent edge with a bead,

Fig. 5 shows another embodiment of a metal stencil according to the invention

with bent edges and

Fig. 6 shows yet another embodiment of a template according to the invention with

separate edge strip for protection.

Detailed description of preferred embodiments

A first embodiment of a metal template 1 according to the invention is shown in a plan view of the underside 6 in Fig. 1. The metal template 1 has a

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not specifically marked actual stencil work area in which the pattern to be printed is introduced, such as by laser cutting, punching or etching. The stencil 1 shown here has four stencil edge areas 2, each of which has a row of openings 3. These openings 3 serve to accommodate corresponding hooking means of a clamping frame not shown here. As already mentioned at the beginning, such a clamping frame can be designed in particular according to the publications mentioned at the beginning.

In the embodiment of a metal stencil according to the invention shown here, the stencil edge regions 2 are separated from adjacent side edge regions 2 by a notch 4. The notches 4 are rectangular in the embodiment shown in Fig. 1, but they can also simply run as an oblique connecting line, as shown in Fig. 5, for example. Curved connecting lines are also conceivable. For example, the edges of the side edge regions 2 can be connected to one another by a radius in the plan view. In this case, this would be referred to as a groove.

According to the invention, the side edge areas 2 are provided with bends 5. The bends 5 extend over the entire length of a side edge area 2, as can be seen from the top view according to Fig. 1. The bends 5 have a certain width in this top view, which is however selected such that the openings 3 are not covered by them or collide with the hooking means of a clamping frame to be inserted into the openings 3. In general, it can be said that the bends 5 should not influence the clamping of a metal template 1.

Fig. 2 shows a schematic cross-sectional view of a bent edge 5 according to Fig. 1. The metal template 1 is shown here with the top side 7 pointing downwards. The bottom side 6 points upwards in the representation according to Fig. 2. The

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The bent edge 5 of the edge region 2 rests against the underside 6. Accordingly, the bend is made by 180°, the radius r at the outer edge of the edge region 2 essentially corresponds to twice the thickness of the template edge region 2.

Fig. 3 shows a cross-section similar to Fig. 2. Here, however, the bent edge 5' is not completely bent in the edge region 2', but only by an angle of 180°-a. Accordingly, the radius r ¹ can be greater than or equal to the radius r according to Fig. 2. In the embodiment shown here, the angle α is still about 30-50°, which simplifies the bending, but already enables a considerable reduction in the risk of injury from a previously sharp edge of a metal template 1 and leads to reduced costs, since the bends can be carried out more quickly and easily.

In order to get from the cross section according to Fig. 3 to that according to Fig. 2, it would now only be necessary to press the edge 5', which has already been bent by approximately 120-140°, against the underside 6 of the metal template 1 according to Fig. 3, which can be done by moving a swivel bending jaw of a corresponding bending tool or by pressing in a separate tool.

Another alternative embodiment of a bent edge 5" is shown in Fig. 4. In the modified edge region 2" here, the bent edge 5" again rests against the underside 6, but a bead 8 is achieved on the outer edge, so that the radius r" is larger than the radius r' and r according to Fig. 3 and 2. This is achieved by specially pressing the tab 5' according to Fig. 3, which reduces the risk of injury even further than according to Fig. 2 and 3.

As already mentioned, Fig. 5 shows a top view of an alternative embodiment of a metal template "&Ggr;" according to the invention. The metal template "&Ggr;" shown here has elongated holes or slotted openings 3'" instead of round holes 3 according to Fig. 1. In addition, the

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Notches 4'" are not rectangular, but only the corner of a template 1'" is cut off. After cutting off these corners to achieve the notches 4"', the edge areas 5'" were bent over; the bends can again be made as shown in Fig. 2, 3 and 4.

By previously cutting off the corners of the metal template 1'", bevels 11 are created at the outer ends of the bent edges 5'". In general, it can be said that the bends or bent edges 5'" in the embodiment according to Fig. 1 neither affect the clamping in the holes 3 or 3'" in a clamping frame, nor lead to twisting or distortion of a clamped template 1'". Furthermore, the template &Ggr;" can correspond in particular to the template according to WO 93/25061.

Finally, it should be noted that it may also be useful not to round off the respective edge of a side edge area by means of a one-piece bend, but to provide a separate protective part in the form of a separate edge strip with a groove for sliding onto the edge area 2 of the template, as shown schematically in Fig. 6. The edge strip 12 can be made of plastic, for example. It is pushed along the edge of the metal template and glued, or adheres by friction.

Claims (11)

1. Stencil with four stencil edge regions ( 2 , 2 ', 2 ", 2 ''') for clamping the stencil (1, 1''') in a clamping frame at at least two opposing stencil edge regions ( 2 , 2 ', 2 ", 2 ''') which are designed to grip and clamp the stencil ( 1 , 1 ''') in the clamping frame, wherein at least one stencil edge region ( 2 , 2 ', 2 ", 2 ''') is rounded off by a bent edge ( 5 , 5 ', 5 ", 5 '''). 2. Template according to claim 1, characterized in that all four template edge regions ( 2 , 2 ', 2 ", 2 ''') are designed to grip and clamp the template ( 1 , 1 ''') in the clamping frame. 3. Template according to claim 1 or 2, characterized in that the template edge regions ( 2 , 2 ', 2 ", 2 ''') designed for gripping and clamping the template ( 1 , 1 ''') in the clamping frame each have a row of openings ( 3 , 3 ''') for receiving suitable hooking devices of the clamping frame. 4. Template according to claim 3, characterized in that the openings for receiving suitable hooking devices of the clamping frame are round holes ( 3 ) or elongated holes ( 3 '''). 5. Stencil according to one of the preceding claims, characterized in that at least those stencil edge regions ( 2 , 2 ', 2 ", 2 ''') which are designed to grip and clamp the stencil ( 1 , 1 ''') in the clamping frame are rounded off by bending the respective associated edge ( 5 , 5 ', 5 ", 5 '''). 6. Template according to one of the preceding claims, characterized in that the bent free edges (5', 5", 5''') are bent by more than 120°. 7. Template according to one of the preceding claims, characterized in that the bent free edges ( 5 , 5 ', 5 ", 5 ''') at least approximately rest on the upper or lower side ( 6 , 7 ) of the template ( 1 , 1 '''). 8. Template according to one of the preceding claims, characterized in that the template edge regions ( 2 , 2 ', 2 ", 2 ''') with bent free edge ( 5 , 5 ', 5 ", 5 ''') have an outer radius of 0.2 mm or more. 9. Stencil according to one of the preceding claims, characterized in that the stencil edge regions ( 2 , 2 ', 2 ", 2 ''') with bent free edge ( 5 , 5 ', 5 ", 5 ''') were additionally subjected to a pressing step, so that the mutually facing sides of the metal stencil ( 1 , 1 ''') run approximately parallel to one another. 10. Template according to one of the preceding claims, characterized in that at least the template edge regions ( 2 , 2 ', 2 ", 2 ''') with bent edge ( 5 , 5 ', 5 ", 5 ''') have a thickness between a minimum of 0.1 mm and a maximum of 1.0 mm, in particular between a minimum of 0.2 mm and 0.4 mm. 11. Template according to one of the preceding claims, characterized in that the entire template ( 1 , 1 ''') consists of metal, in particular stainless steel.