DE102021107369A1 - Optimized punched grid arrangement - Google Patents

Abstract

The invention relates to a stamped grid (1) for a light module, in particular for the interior and/or interior lighting of a motor vehicle, having a plurality of serially arranged connection sections (10) which are each designed to be connected to a light source (2). characterized in that the stamped grid (1) has at least two conductor tracks (20) which together have a first common overall conductor cross section A1GES and at least a number N of separate data lines (30) which together have a common overall conductor cross section A2GES that differs from the first overall conductor cross section A1GES.

Description

This invention relates to an optimized lead frame arrangement, in particular a lead frame for electrical connection, which is optimized with regard to mechanical and electrical properties.

There are a number of solutions in the prior art for producing electrically conductive pressed screens. Stamped grids are known, for example, which are used in areas of an electrical network, in particular in a motor vehicle, in which conductive elements and current paths with a high current-carrying capacity and sufficient inherent stability are required. A stamped grid is produced from a sheet-like starting material, such as sheet metal, in particular sheet copper.

Electrically conductive current paths and contact elements, such as plug contacts, spring contacts or clamping contacts and conductor tracks, are formed by shaping methods, in particular stamping and/or bending, with the contact elements typically being formed at the conductor track ends of the conductor tracks. The person skilled in the art is also aware that a stamped grid (also known as a punch grid) does not have to be understood as a grid in the narrow sense of the word, but rather that various stamped geometries also come under this term.

Stamped grids are known from the prior art, for example, which have contact tongues arranged in rows for electrical contacting and/or electrical connection to an electrical device, such as a printed circuit board (PCB). In particular when used in some applications, such as vehicle applications, a stamped grid of a motor vehicle electrical system is exposed to high temperature fluctuations and/or vibrations. These can e.g. B. lead to cracks appearing in the solder joints and the solder joints break and electrical contact between the stamped grid and the printed circuit board is lost. This happens, for example, when the stamped grid is exposed to different temperatures on different sides, so that a high temperature occurs on one side and a lower temperature on the other side of the stamped grid. The contact tongues that are in the high temperature range expand more than the contact tongues that are in the lower temperature range, causing a relative movement of the stamped grid to the printed circuit board. This creates high tension and forces in the solder joints and at the connection points, which can lead to damage.

Embodiments are known from the prior art which partially but incompletely solve the problem described above. For this purpose, the contact tongues have a C, V, or U-shaped curvature. The contact tongues designed in this way allow, on the one hand, temperature-related different expansions of the contact tongues and thus a relative movement between the stamped grid and the printed circuit board, and on the other hand, vibrations can be damped. However, the contact tongues must not be arranged too close together, otherwise the curvature of one contact tongue will protrude into the area of an adjacent contact tongue.

From the utility model specification DE 202 14 126 U1 a circuit arrangement with a stamped grid is already known, the stamped grid having fork-shaped plug-in contact elements which can be arranged in different planes. From the disclosure document US 6,445,584 B1 a stamped grid is also known which has rod-shaped contact tongues.

From the DE 10 2004 020085 A1 a method for producing a stamped grid is known, which is embedded in plastic in an injection mold. The stamped grid is fixed during an injection molding process at a fixing point with a fixing element, so that the shape of the stamped grid is preserved during the injection molding process. A plastic element, which is surrounded by the injected plastic, is used as the fixing element.

The pamphlet WO 2018/069301 A relates to an LED assembly with a flexible conductor arrangement (flexible lighting strip). the DE10134381A1 relates to a light source carrier, preferably for vehicle lights, with at least one LED, in particular a high-power LED, which is mechanically and electrically connected to the carrier, the light source carrier being a metal stamped grid on which at least two folded areas are arranged for each LED and wherein each contact lug of the at least one LED is arranged resiliently and clampingly and under pretension between the legs of a folded area and bears against the stamped grid over a large area. Efficient heat dissipation is ensured here by the large contact area between the LED contact lugs and the metal stamped grid.

the DE 20008346 U1 deals with a solution in which the contact plates are held at a distance from one another by an electrically insulating carrier. The advantage achieved in this way is that the heat dissipation from the electrical component to the environment is significantly improved by the large thickness or cross-sections of the contact plates (approx. 0.2 to approx. 1 mm) compared to the copper coating of a conventional circuit board. This allows a significant increase in the maximum permissible LED current and a reduction in the number of LEDs required, so that costs are saved.

The not yet published registration DE 10 2019 009034 relates to a light module in which the carrier is formed from a stamped grid. This eliminates the large number of printed circuit boards and their error-prone connection using stranded wires. The light module is advantageously of simpler design and is therefore more cost-effective. Furthermore, the light module also offers greater operational and/or functional reliability.

It is also described that the stamped grid can consist of a material with high electrical conductivity and/or thermal conductivity, which further increases the operational reliability of the light module. The metal for the pressed screen can be copper, copper beryllium or the like.

For the purpose of designing the light module in the form of a strip, a multiplicity of successive light sources can be provided. The light sources are expediently light-emitting diodes, which are particularly energy-efficient. The light sources can be soldered onto the stamped grid in a simple manner. In a compact design, an electronic module for controlling the light source can be electrically connected to the stamped grid. After soldering, the bridges in the stamped grid are separated so that electrical short circuits are prevented. If necessary, the bars are then overmoulded with plastic for stabilization. Subsequently or optionally, the light sources are overmoulded with the optically transparent plastic, such as silicone, polyurethane (PU), polycarbonate (PC) or the like.

However, the concepts known in the prior art all represent concepts which in any case do not adequately solve the said problems and do not provide the optimal mechanical and electrical properties of a stamped grid. The aim is on the one hand to improve the deformability of a conductor track in the form of a stamped grid and at the same time to ensure both the conductivity of electrical energy (resistance as small as possible) and the thermal conductivity to ensure sufficient dissipation of the heat that occurs.

Against this background, the present invention is based on the technical problem of providing a solution for improving the mechanical, electrical and thermal properties of a stamped grid.

The technical problem described above is solved by subject matter as defined by the independent claims.

A basic idea of the present invention relates to the geometric adjustment of a stamped grid for optimization with regard to the greatest possible deformability and the support of the current and heat conduction. The mechanical deformability is improved by minimized cross sections, but the thermal and electrical conductivity is reduced. The disadvantage of minimizing the cross-sections is the strength. The invention optimizes the geometry and cross-sections of the pressed screen in order to find a relative optimum of at least these two factors.

According to the invention, a stamped grid for a light module, in particular for the interior and/or interior lighting of a motor vehicle, is proposed with a plurality of connection sections arranged in series one behind the other, which are each designed to be connected to a light source (e.g. an LED). The stamped grid has at least two conductor tracks which together have a first common overall conductor cross section A1 and at least a number N of separate data lines which together have a common overall conductor cross section A2 that differs from the first overall conductor cross section A1.

In an advantageous embodiment of the invention, it is provided that the pressed screen extends in a strip-like or band-like manner along its longitudinal direction L and the two conductor tracks for supplying current and voltage to the light sources run along the longitudinal direction L without being severed or interrupted.

In other words, the stamped grid forms two essentially parallel, continuous conductor tracks for supplying voltage to the light sources or LEDs, which preferably run on the outside.

It is also advantageous if the data lines run locally in an area between the two (external) conductor tracks and, in particular, have contact ends (eg contact pins) on the connection sections for electrically connecting the light sources.

wobei k ein Wert zwischen 2 und 8 ist und N die Anzahl der Datenleitungen des Stanzgitters angibt, die jeweils zusätzlich zu den stromführenden bzw. spannungsführenden Leiterbahnen vorgesehen sind.In a particularly advantageous embodiment of the invention, it is provided that the ratio V of the total conductor cross section A1 _GES of the conductor tracks (to power the light sources or LEDs) to the total conductor cross section A2 _GES of the signal lines is determined according to the following formula: $$\text{V}\left(\text{k}\text{,n}\right)=\frac{A1\text{TOTAL}}{A2\text{TOTAL}}=\text{k}\cdot {\text{N}}^{-1}$$

where k is a value between 2 and 8 and N indicates the number of data lines of the stamped grid that are provided in addition to the current-carrying or voltage-carrying conductor tracks.

Also advantageous is an embodiment in which the following applies to k: k≈3.1.

In a likewise advantageous embodiment of the invention, it is provided that the respective connection sections (light source contacting sections) are provided with holding sections that protrude laterally in the stamped grid plane, which on the one hand serve as pilot strips for the tape transport and at the same time form fastening sections for the stamped grid. When processing in the "roll-to-roll process", so-called pilot strips are usually provided for the tape transport, which in the present case, however, has an additional function.

It is also advantageous if the data lines and the signal lines form a line section bent in a V-shape, S-shape, U-shape or non-linearly at a common position between the respective connection sections for the light sources, in which the data lines and the signal lines are either protrude together from the stamped grid plane or have at least two changes in direction in the stamped grid plane. This area forms a mechanical flex zone, by means of which the stamped grid can absorb thermal expansion or at least partially eliminate the stresses from the stamped grid.

Also as a material, a preferred material is copper-chromium-zirconium for the pressed screen.

1. a) An den jeweiligen Anschlussabschnitten werden Leiterplatten für oder mit den Lichtquellen bestückt und elektrisch mit den Datenleitungen und den Signalleitungen verbunden und danach erfolgt
2. b) das Umbiegen der Datenleitungen und der Signalleitungen zwischen den Anschlussabschnitten des Stanzgitters zur Herstellung der oben genannten Flex-Zone.

A further aspect of the present invention, in addition to the stamped grid, relates to a method for producing a light module, preferably with a stamped grid as described above, with the following steps:

1. a) Printed circuit boards for or with the light sources are fitted to the respective connection sections and electrically connected to the data lines and the signal lines, and then this is done
2. b) the bending of the data lines and the signal lines between the connection sections of the stamped grid to produce the above-mentioned flex zone.

1. a) An den jeweiligen Anschlussabschnitten werden Umspritzungen zur mechanischen Halterung der Datenleitungen und/oder der Signalleitungen ausgebildet;
2. b) Umbiegen der Datenleitungen und der Signalleitungen zwischen den Anschlussabschnitten des Stanzgitters zur Herstellung der oben genannten Flex-Zone und
3. c) Bestückung des Stanzgitters mit Lichtquellen an den Anschlussabschnitten.

Another aspect of the present invention, in addition to the method mentioned, relates to an alternative method with the following steps:

1. a) Encapsulations for mechanically holding the data lines and/or the signal lines are formed on the respective connection sections;
2. b) Bending the data lines and the signal lines between the connection sections of the stamped grid to produce the above-mentioned flex zone and
3. c) Equipping the stamped grid with light sources at the connection sections.

In an alternative embodiment of this last-mentioned method, an alternative mechanical mounting of the data lines and/or the signal lines is provided instead of the encapsulation, preferably by mounting devices, tape solutions or temporarily provided holding devices.

Other advantageous developments of the invention are characterized in the dependent claims or are presented in more detail below together with the description of the preferred embodiment of the invention with reference to the figures.

• 1 eine schematische Draufsicht auf ein erfindungsgemäßes Stanzgitter;
• 2 eine schematische Draufsicht des Stanzgitter aus 1 nach dem Durchtrennen von Verbindungsstegen und dem Abtrennen eines Teils des Pilotstreifens;
• 3 eine Grafik, die den Zusammenhang der Querschnittsverhältnisse abhängig von der Anzahl N der Datenleitungen verdeutlicht;
• 4 eine schematische Schnittansicht gemäß der Ausführung aus 1.

Show it:

• 1 a schematic plan view of a pressed screen according to the invention;
• 2 a schematic plan view of the lead frame 1 after severing tie bars and severing part of the pilot strip;
• 3 a graphic that illustrates the relationship between the cross-sectional ratios as a function of the number N of data lines;
• 4 FIG. 12 is a schematic sectional view according to the embodiment 1 .

The invention is described in more detail below using an exemplary embodiment with reference to the figures, with the same reference symbols indicating the same functional and/or structural features.

the 1 shows a schematic plan view of a stamped grid 1 according to the invention. The stamped grid 1 is designed for a light module with a plurality of serially arranged connection sections 10 one behind the other. The connection sections 10 are designed as electrical connection zones for the LEDs or light sources. The light sources 2 can be electrically connected to these connection sections 10 .

The stamped grid 1 is made from a stamped strip and has a pilot strip P with catch holes 4 for the feed of the stamping machine.

The two outer lines represent the traces 20 which, with reference to Table 1, represent the power and ground lines.

Between them are two data lines 30, which are narrower in width than the width of the conductor tracks 20. The connecting webs 5 are punched freely, as is the case in FIG 2 recognizes. The pilot strip P is also separated in a later process step. The catching holes 4 of the pilot strip P remain on the connection sections 10.

The encapsulations 50 are used for the mechanical connection of the conductor tracks 20 and the data lines 30 after the connecting webs 5 have been punched free. Also shown is the curved flex zone.

The stamped grid 1 has the two conductor tracks 20, which together have a first common overall conductor cross section A1 and at least a number N of separate data lines 30, which together have a common overall conductor cross section A2 _GES that differs from the first overall conductor cross section A1 _GES . In the 1 and 2 two data lines 30 are shown in each case.

Below is an example of geometries of a stamped grid 1 with 4 signal lines 30 (Data_1 to Data_4) for three different widths (width 1, width 2 and width 3). The strip conductors 20 provided for the current and voltage supply of the light sources are indicated here with V_Supply and ground. Management Thickness [mn Width 1 [r Width 2 [r Width 3 [r A 1 [mm ² ] A 2 [mm ² ] A 3 [mm ² ] 1 V_supply 0.15 0.7 1.1 2 0.105 0.165 0.3 2 Data_1 0.15 0.7 0.7 0.5 0.105 0.105 0.075 3 Data_2 0.15 0.7 0.7 0.5 0.105 0.105 0.075 4 Data_3 0.15 0.7 0.7 0.5 0.105 0.105 0.075 5 Data_4 0.15 0.7 0.7 0.5 0.105 0.105 0.075 6 mass 0.15 0.7 1.1 2 0.105 0.165 0.3

Depending on the number N of data lines, there are different values for the cross-sectional area ratio V = A1 _GES / A2 _GES , where A1 _GES is the sum of the cross-sections of the conductor tracks 20 and A2 _GES is the sum of the cross-sections of the signal lines 30 (Data_1 to Data_4). Cross-sectional area ratio depending on the data lines 1.00 2.00 3.00 4.00 data lines 1: min 2.00 1.00 0.67 0.50 2: preference 3:14 1.57 1.05 0.79 3: max 8.00 4.00 2.67 2.00

Graphically, the relationship is in the 3 shown. Mathematically, this means for the optimized ratio V for the number N of signal lines 30: $$\text{V}\left(\text{k}\text{,n}\right)=\frac{A1\text{<figure-callout id="2" label="TOTAL A" filenames="DE102021107369A1\_0004.png,DE102021107369A1\_0006.png" state="{{state}}">TOTAL</figure-callout>}}{A}=\text{k}\cdot {\text{N}}^{-1}$$

In the 4 A schematic sectional view is shown to illustrate the implementation of a flex zone with a U-bent duct section (FZ).

The implementation of the invention is not limited to the preferred exemplary embodiments specified above. Rather, a number of variants are conceivable which make use of the solution shown even in the case of fundamentally different designs.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 20214126 U1 [0006]
• US6445584B1 [0006]
• DE 102004020085 A1 [0007]
• WO 2018/069301 A [0008]
• DE 10134381 A1 [0008]
• DE 20008346 U1 [0009]
• DE 102019009034 [0010]

Claims (10)

Stamped grid (1) for a light module, in particular for the interior and/or interior lighting of a motor vehicle, with a plurality of connection sections (10) arranged in series one behind the other, which are each designed to be connected to at least one light source (2), characterized characterized in that the stamped grid (1) has at least two conductor tracks (20) which together have a first common overall conductor cross section A1 _Ges and at least a number N of separate data lines (30) which together have a common overall conductor cross section A2 that differs from the first overall conductor cross section A1 _GES have _GES . Punched grid (1) according to claim 1 , characterized in that the stamped grid (1) extends in a strip-like or band-like manner along its longitudinal direction L and the two conductor tracks (20) for supplying current and voltage to the light sources (2) run along the longitudinal direction L without being severed. Punched grid (1) according to claim 1 or 2 , characterized in that the data lines (30) run locally between the two conductor tracks (20) in an area and in particular have contact ends (21) on the connection sections (10) for electrically connecting the light sources (2). Stamped grid (1) according to one of the preceding claims, characterized in that the ratio V of the total conductor cross section A1 _GES of the conductor tracks (20) to the total conductor cross section A2 _GES of the signal lines (30) is determined according to the following formula: $$\text{V}\left(\text{k}\text{,n}\right)=\frac{A1\text{TOTAL}}{A2\text{TOTAL}}=\text{k}\cdot {\text{N}}^{-1}$$

where k is a value between 2 and 8 and N indicates the number of data lines (30). Punched grid (1) according to claim 4 , characterized in that the following applies to k: k ≈ 3.1. Stamped grid (1) according to one of the preceding claims, characterized in that holding sections (3) which protrude laterally in the stamped grid plane are provided on the respective connecting sections (10) and which on the one hand serve as pilot strips for the tape transport and at the same time are fastening sections for the stamped grid (1) form. Stamped grid (1) according to one of the preceding claims, characterized in that the conductor tracks (20) and the signal lines (30) between the respective connection sections (10) for the light sources (2) each have a V-shaped, S-shaped, U-shaped form a line section (flex zone) that is curved in a shaped or non-linear manner, in which the conductor tracks (20) and the signal lines (30) either protrude from the stamped grid plane or have at least two changes in direction in the stamped grid plane. Method for producing a light module (1), preferably with a stamped grid (1) according to one of the preceding ones Claims 1 until 6 , characterized in that a. printed circuit boards (40) for or with the light sources (2) are electrically connected to the conductor tracks (20) and the signal lines (30) on the respective connection sections (10) and b. the strip conductors (20) and the signal lines (30) are bent between the connection sections (10) of the stamped grid (1) in order to produce the features claim 7 . Method for producing a light module (1), preferably with a stamped grid (1) according to one of the preceding ones Claims 1 until 6 , characterized in that a. forming encapsulations (50) on the respective connection sections (10) for mechanically holding the conductor tracks (20) and/or the signal lines (30) and then b. the strip conductors (20) and the signal lines (30) are bent between the connection sections (10) of the stamped grid (1) in order to produce the features claim 7 and after that c. the lead frame (1) is equipped with light sources (2) at the connection sections (10). procedure after claim 9 , characterized in that in step a) instead of the encapsulation (50), an alternative mechanical mounting of the conductor tracks (20) and/or the signal lines (30) takes place, preferably by means of mounting devices, tape solutions or temporary hatches.

Images