Search

EP-4740703-A1 - FLEXIBLE LED STRIP

EP4740703A1EP 4740703 A1EP4740703 A1EP 4740703A1EP-4740703-A1

Abstract

The present invention relates to a flexible LED strip (1) having: a flexible circuit board (2) extending longitudinally along a longitudinal extent (L), electrical conductor tracks (3) which are provided on the circuit board (2), components (4) at least having an LED chip (40), wherein the components (4) are fastened to the circuit board (2) and are each electrically connected to at least one of the conductor tracks (3), and terminal contact points (6) for the electrical connection of external terminal contacts (8) to the conductor tracks (3), wherein the terminal contact points (6) are each at least partially covered with solder (5) of a soldering paste that has been melted and hardened again, and electrically connected.

Inventors

  • KERBER, STEFAN
  • MÜHLBACHER, Gerd
  • HECHENBERGER, CLAUS
  • ANNA, Szücs

Assignees

  • Tridonic GmbH & Co. KG

Dates

Publication Date
20260513
Application Date
20240820

Claims (20)

  1. 1. Flexible LED strip (1), comprising, • a flexible printed circuit board (2) extending longitudinally along a longitudinal extent (L), • electrical conductor tracks (3) provided on the circuit board (2), • Components (4) comprising at least one LED chip (40), wherein the components (4) are mounted on the circuit board (2) and are each electrically connected to at least one of the conductor tracks (3), and • Connection contact points (6) for the electrical connection of external connection contacts (8) to the conductor tracks (3), wherein the connection contact points (6) are at least partially covered and electrically connected by means of reflow soldering with melted and recurred solder (5) of a solder paste.
  2. 2. Flexible LED strip (1) according to claim 1, wherein the connection contact points (6) are completely covered with the solder (5) and electrically connected.
  3. 3. Flexible LED strip (1) according to one of the preceding claims, wherein at least one of the connection contact points (6) is provided adjacent to at least one or both narrow end edges (20) of the printed circuit board (2) opposite one another with respect to the longitudinal extent (L).
  4. 4. Flexible LED strip (1) according to one of the preceding claims, wherein a plurality of connection contact points (6) are provided distributed along the longitudinal extent (L).
  5. 5. Flexible LED strip (1) according to the preceding claim, wherein the plurality of connection contact points (6) are provided distributed at regular intervals along the longitudinal extent (L).
  6. 6. Flexible LED strip (i) according to one of the preceding claims, wherein the flexible LED strip (1) has at least one predetermined separation section (7) along its longitudinal extent (L) or a plurality of predetermined separation sections (7) distributed along its longitudinal extent (L), at which or at which the LED strip (1) can be separated transversely to the longitudinal extent (L) into a plurality of flexible partial strip sections (10).
  7. 7. Flexible LED strip (1) according to the preceding claim, wherein the plurality of predetermined separation sections (7) are provided distributed at regular intervals along the longitudinal extent (L).
  8. 8. Flexible LED strip (1) according to one of the two preceding claims, wherein at least one of the connection contact points (6) is provided adjacent to the predetermined separation section (7) or to the predetermined separation sections (7).
  9. 9. Flexible LED strip (1) according to the preceding claim, wherein at least one of the connection contact points (6) is provided adjacent to the intended separation section (7) or to the intended separation sections (7) in such a way that after the flexible LED strip (1) has been separated at the respective intended separation section (7) into the plurality of partial strip sections (10), these connection contact points (6) are arranged adjacent to a further narrow end edge (11) of these partial strip sections (10) produced by the separation.
  10. 10. Flexible LED strip (1) according to one of the preceding claims, wherein the components (4) comprise COB components (42).
  11. 11. Flexible LED strip (1) according to the preceding claim, wherein at least one of the COB components (42) comprises the LED chip (40), wherein the LED chip (40) is covered with a phosphor matrix (12).
  12. 12. Flexible LED strip (1) according to the preceding claim, further comprising a dam (13) which laterally delimits or circumferentially surrounds the LED chip (40) and is filled with the phosphor matrix (12).
  13. 13- Flexible LED strip (1) according to the preceding claim, wherein the dam (13) is made of an epoxy resin or a silicone resin.
  14. 14. Flexible LED strip (1) according to one of the two preceding claims, wherein the dam (13) is reflective, and/or wherein the dam (13) is non-transparent at least for the wavelength of the light emitted by the LED chip (40) and/or the light then converted in the phosphor matrix (12).
  15. 15. Flexible LED strip (1) according to one of the preceding claims, wherein the components (4) comprise surface-mounted components (41).
  16. 16. Flexible LED strip (1) according to the preceding claim, wherein at least one of the surface-mounted components (41) comprises the LED chip (40).
  17. 17. Flexible LED strip (1) according to one of the preceding claims, wherein the components (4) are fastened to the circuit board (2) by means of reflow soldering via melted and recurred solder (5) of the solder paste and are each electrically connected to at least one of the conductor tracks (3).
  18. 18. Flexible LED strip (1) according to one of the preceding claims, wherein the conductor tracks (3) are made of copper or a copper alloy.
  19. 19. Flexible LED strip (1) according to one of the preceding claims, wherein the connection contact points (6) are made of copper or a copper alloy.
  20. 20. Flexible LED strip (1) according to one of the preceding claims, wherein the solder (5) consists of tin or a tin alloy.

Description

Flexible LED strip Description: The present invention relates to a flexible LED strip with connection contact points for the electrical connection of external connection contacts and to a light strip system with such a flexible LED strip and a connection contact to be connected thereto. Flexible LED strips are generally known from the prior art. For this purpose, a large-area printed circuit board component is typically manufactured and then divided into narrow and elongated LED strips. The printed circuit board component is first provided with the appropriate electrical conductors and contact points. The surface is then coated with an organic surface protection agent (also called an "organic solderability preservative" (OSP)). This layer consists of organic substances such as benzotriazole, imidazole, or benzimidazole, which protect the conductors and contact points—for example, those made of copper—from oxidation. In the next step, appropriate electrical/electronic components or electrical conductors can be soldered onto the circuit board or contact points. For example, electrical conductors in the form of an electrical cable with a stripped end can be soldered directly onto the circuit board. Alternatively or additionally, it is conceivable to provide chip-on-board (COB) components (e.g., COB LEDs). In this case, LED chips are attached to the circuit board, e.g., in flip-chip assembly. The LED chips are covered with a phosphor matrix. Optionally, the LED chips can first be surrounded laterally with a dam (e.g., made of silicone resin), which is then filled with the phosphor matrix, thus encapsulating the LED chip. The phosphor matrix and, if present, the dam material are then cured in one step (or alternatively in separate steps) (curing step). Alternatively or additionally, it is conceivable that in a first step, solder paste is applied to the printed circuit board component – for example, using a screen printing process – particularly to conductor track sections. Subsequently, corresponding surface-mounted components (SMD) are placed on the printed solder paste areas. In a subsequent reflow soldering process, the solder paste containing the components is The assembled circuit board is heated sufficiently to melt the solder contained in the solder paste, while the increased temperature simultaneously activates the flux in the solder paste gel. This secures the surface-mounted components to the circuit board. The circuit board component can then be cut open to separate the individual flexible LED strips. These can then be rolled up in a final step, if required. Depending on the assembly and design of the flexible LED strip, it is then possible to divide it into smaller sub-strips. Since the heat introduced during reflow soldering and/or the curing of the phosphor matrix and, if applicable, dam material, in particular, leads to damage of the organic surface protection, the connection contact points are often partially exposed and oxidize. This, in turn, reduces the subsequent electrical connection of a connection contact via these connection contact points. To keep the connection contact points permanently and efficiently electrically conductive, even when reflow soldering or curing is used, the surface of the connection contact points is usually treated. These are often coated with chemical silver, chemical gold, or even chemical tin. Such coatings are comparatively expensive but enable highly effective electrical conductivity even after reflow soldering or curing. It is therefore an object of the present invention to provide a flexible LED strip and a light strip system equipped therewith, which can be produced cost-effectively, while the connection contact points simultaneously retain effective electrical conductivity. This object is achieved by the subject matter of the independent claims. The dependent claims develop the central idea of the present invention in a particularly advantageous manner. According to a first aspect, the present invention relates to a flexible LED strip. This has a flexible printed circuit board extending longitudinally along a longitudinal extent. The flexible LED strip further has electrical conductor tracks provided on the printed circuit board. In addition, the flexible LED strip has components (e.g., COB components such as COB LEDs or surface-mounted components), which in turn have at least have an LED chip for emitting light. The components (e.g., surface-mounted or mounted using COB technology) are attached to the circuit board and each electrically connected to at least one of the conductor tracks. The flexible LED strip further has connection contact points for electrically connecting external connection contacts to the (i.e., at least one of the) conductor tracks (and thus preferably to the components). The connection contact points are at least partially covered with melted and recurred solder from a solder paste by means of reflow soldering and are electrically