Double-layer circuit board and LED lamp strip
By creating vias on a double-layer circuit board and combining hot pressing or etching to form a second circuit layer, the problem of solder voids is solved, yield is improved and maintenance costs are reduced.
Patent Information
- Application Number
- CN202520190191.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-07
- Publication Date
- 2026-02-10
- Estimated Expiration
- 2035-02-07
AI Technical Summary
In existing technologies, solder voids exist during the soldering of double-layer circuit boards, leading to poor conductivity, resulting in a high defect rate and high maintenance costs for LED strip production.
The method involves forming vias on a circuit board with an insulating film and creating a second circuit layer by hot pressing or etching. This allows the second layer to bond with the first insulating film at some or all of the vias, avoiding the repulsion of the tin by the intermediate insulating material and ensuring that the tin can flow smoothly onto the two circuit metal layers.
It effectively reduces or avoids solder voids, improves the yield of circuit boards, and reduces maintenance costs.
Smart Images
Figure CN223899424U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to light strips, specifically a double-layer circuit board and an LED light strip. Background Technology
[0002] A double-layer circuit board has two layers of circuitry separated by an insulating layer. However, the two layers of circuitry need to be interconnected. One existing interconnection method is as follows:
[0003] The intermediate insulating layer, the upper circuit layer, and the adhesive layer are drilled together and then pasted onto the back circuit; alternatively, adhesive is applied to the back of the single-sided copper-clad board, then holes are drilled and it is pasted onto the copper foil, and then etched to form two layers of circuitry. See details. Figure 1.1 As shown, the cup-hole 1' produced by the above two methods has a lower layer of circuit metal 2' at the bottom and an upper layer of circuit metal 3' at the edge of the hole. When using this type of board, solder paste is applied to the cup-hole, and after reflow soldering, the upper and lower metal layers are soldered together at the cup-hole. This method has been promoted and used in the circuit board industry by the inventor, especially for making LED strip circuit boards, and has been in mass production for over ten years. However, it has always had serious defects such as insufficient solder application to the cup-hole or the formation of solder voids after soldering, such as... Figure 1.2 As shown, there is a solder cavity 5' below the solder 4', which causes many vias to become non-conductive after SMT soldering, requiring manual repair to restore conductivity. See details. Figure 1.3 As shown, even after soldering the component pin 6', the metal of the upper and lower layers of circuitry could not be connected; some of the vias were not visible because they were filled with solder voids, while a small amount of solder connected the upper and lower layers of circuitry. However, when the LED strip was used by the user, the connection would fail if it was bent even slightly, and the LED would not light up.
[0004] The inventors discovered that the poor conductivity and voids in the solder bowls are caused by the repulsive effect of the insulating material 7' in the middle of the bowl wall on the solder, resulting in voids or gaps. Even when the lower metal layer is pushed to the bowl hole, flush or nearly flush with the upper metal layer, gaps still exist between the upper and lower metal layers. In particular, the gaps are often larger due to tolerances in the mold and inaccurate pushing. After soldering, the upper and lower metal layers cannot be guaranteed to be 100% effective connected. Moreover, a typical LED strip is at least 5 meters long, with at least several hundred bowl holes that need to be soldered for conductivity. Currently, every LED strip has poor soldering in the bowl holes during production, requiring repairs, resulting in a high defect rate and high repair costs. Utility Model Content
[0005] The present invention aims to solve at least one of the problems of the prior art. To this end, the present invention provides a double-layer circuit board and LED light strip, which can avoid solder voids and improve the yield.
[0006] The technical solution adopted by this utility model to solve its technical problem is:
[0007] In a first aspect, embodiments of this utility model provide a method for manufacturing a double-layer circuit board, comprising:
[0008] On the first insulating film with adhesive, wires are attached to form the first circuit layer; or, metal foil is attached, die-cut, and the unwanted metal is peeled off to form the first circuit layer.
[0009] Die-cut the insulating film with adhesive on both sides to form a through hole;
[0010] The metal foil is attached to the middle insulating film, then the metal foil is die-cut, and the unwanted metal is peeled off to form the second circuit layer;
[0011] The top layer of adhesive-coated second insulating film is die-cut to form solder pad windows;
[0012] After aligning and bonding the first insulating film with the first circuit layer, the intermediate insulating film with the second circuit layer, and the second insulating film with the pad window, they are hot-pressed to form a circuit board, so that the second circuit layer is bonded to the first insulating film at some or all of the vias.
[0013] In a first aspect, another embodiment of this utility model also provides a method for manufacturing a double-layer circuit board, comprising:
[0014] On the first insulating film with adhesive, wires are attached to form the first circuit layer; or, metal foil is attached, die-cut, and the unwanted metal is peeled off to form the first circuit layer.
[0015] Die-cut the insulating film with adhesive on both sides to form a through hole;
[0016] A protective film is attached to one side of the intermediate insulating film, and a metal foil is attached to the other side. After hot pressing, the metal foil on the intermediate insulating film is etched using an etching method to obtain the second circuit layer. Then the protective film is peeled off.
[0017] After aligning and bonding the first insulating film with the first circuit layer to the intermediate insulating film with the second circuit layer, hot pressing is performed to bond the second circuit layer to the first insulating film at some or all of the through holes.
[0018] An ink solder resist layer is fabricated on the second circuit layer.
[0019] The first aspect of this utility model has at least one of the following beneficial effects: In this embodiment, a circuit board is formed by hot-pressing a first insulating film with a first circuit layer, an intermediate insulating film with a second circuit layer, and a second insulating film with solder pad windows, after alignment and bonding. This allows the second circuit layer to bond to the first insulating film at some or all of the vias. Alternatively, a circuit board is formed by hot-pressing a first insulating film with a first circuit layer and an intermediate insulating film with a second circuit layer, after alignment and bonding. This allows the second circuit layer to bond to the first insulating film at some or all of the vias. Thus, the two metal circuit layers are close to, in contact with, or overlap each other at some or all of the vias. The second circuit layer partially blocks the intermediate insulating film within the vias, preventing the intermediate insulating material blocked by the second circuit layer from repelling the solder during soldering. The solder can then flow smoothly onto the two metal circuit layers, reducing or avoiding solder voids and effectively improving the yield of the circuit board.
[0020] Secondly, this utility model embodiment provides a double-layer circuit board, comprising:
[0021] The first insulating film is the solder resist layer on the back side;
[0022] The first circuit layer is bonded to the first insulating film. The first circuit layer consists of circuits of uniform width or circuits of inconsistent width. The first circuit layer contains at least two main circuits longer than 1 meter.
[0023] An intermediate insulating film has a through hole on it, and a first circuit layer is exposed from the through hole at the through hole;
[0024] The second circuit layer is bonded to the intermediate insulating film. At some or all of the vias, the circuits of the second circuit layer are bonded to the first insulating film. The second circuit layer partially blocks the intermediate insulating film inside the vias.
[0025] A front solder mask layer is bonded to the second circuit layer. The front solder mask layer has pad windows, some of which are located at the vias. Each pad window at the via exposes both the metal of the first circuit layer and the metal of the second circuit layer; or, at the vias, some pad windows expose both the metal of the first circuit layer and the metal of the second circuit layer, while others expose only the metal of the first circuit layer.
[0026] Optionally, the front solder resist layer is an insulating film or solder resist ink.
[0027] Optionally, the thickness of the first circuit layer is greater than or equal to the thickness of the second circuit layer;
[0028] Optionally, the second line layer may consist of multiple secondary lines, or the second line layer may include a main line and multiple secondary lines.
[0029] Optionally, at the via, both the first and second circuit layers are bonded to the first insulating film and have formed pads. The metal of the first and second circuit layers are close to each other or in contact from side to side, or the metal portion of the second circuit layer overlaps on the first circuit layer.
[0030] Optionally, at the via, only the pad formed by the first line layer metal is used to solder one of the components, or as a shear pad.
[0031] Thirdly, this utility model provides an LED light strip, including the double-layer circuit board described in any of the embodiments of the second aspect above. Electronic components are soldered onto the double-layer circuit board, and component leads are soldered to the pads at some or all of the vias. The pads at the vias where component leads are soldered are combined pads formed by a combination of the first circuit layer metal and the second circuit layer metal; or, the pads at the vias where component leads are soldered are the first circuit layer metal; or, the pads at the vias are only soldered with tin.
[0032] The second and third embodiments of this utility model have at least one of the following beneficial effects: By bonding the second circuit layer to the intermediate insulating film, the circuits of the second circuit layer are bonded to the first insulating film at some or all of the vias. The second circuit layer partially blocks the intermediate insulating film inside the vias, so that when the circuit board is soldered, the intermediate insulating material blocked by the second circuit layer will not repel the solder, and the solder can flow smoothly to the two circuit metal layers, reducing or avoiding solder voids and effectively improving the yield of the circuit board. Attached Figure Description
[0033] Figure 1.1 This is a schematic diagram of the cross-sectional structure of a traditional circuit board at the location of a via.
[0034] Figure 1.2 yes Figure 1.1 A schematic diagram of the structure after soldering.
[0035] Figure 1.3 yes Figure 1.2 A schematic diagram of the structure after welding the component pins shown;
[0036] Figure 2.1 This is a schematic diagram of the planar structure of the first insulating film in the first embodiment of this utility model;
[0037] Figure 2.2 Is Figure 2.1 The diagram shows a planar structure after the first circuit layer has been fabricated on the first insulating film.
[0038] Figure 2.3 This is a schematic diagram of the planar structure of the intermediate insulating film with through holes in the first embodiment of this utility model;
[0039] Figure 2.4 Is Figure 2.3 The diagram shows a planar structure after a second circuit layer has been fabricated on the intermediate insulating film.
[0040] Figure 2.5 This is a schematic diagram of the planar structure of the second insulating film with solder pad windows in the first embodiment of this utility model;
[0041] Figure 2.6 It is Figure 2.2 , Figure 2.4 and Figure 2.5 The diagram shows the planar structure of the circuit board formed after the structures are bonded together.
[0042] Figure 2.7 yes Figure 2.6 A cross-sectional view of the shear pad location (the first and second circuit layers do not overlap at the vias).
[0043] Figure 2.8 yes Figure 2.6 A cross-sectional view of the shear pad location (the first and second circuit layers overlap at the vias).
[0044] Figure 3.1 This is a schematic diagram of the planar structure of the first insulating film in the second embodiment of this utility model;
[0045] Figure 3.2 Is Figure 3.1 The diagram shows a planar structure after the first circuit layer has been fabricated on the first insulating film.
[0046] Figure 3.3 This is a schematic diagram of the planar structure of the intermediate insulating film with through holes in the second embodiment of this utility model;
[0047] Figure 3.4 Is Figure 3.3 The diagram shows a planar structure after a second circuit layer has been fabricated on the intermediate insulating film.
[0048] Figure 3.5 This is the second embodiment of the present invention. Figure 3.3 An exploded view of the structure shown (before etching);
[0049] Figure 3.6 yes Figure 3.5 A schematic diagram of the cross-sectional structure after the combination of the structures shown.
[0050] Figure 3.7 It is Figure 3.2 , Figure 3.4 The diagram shows the planar structure of the circuit board formed after the structures are bonded together.
[0051] Figure 3.8 yes Figure 3.7 The diagram shown is a planar structure after the ink solder resist layer has been fabricated.
[0052] Figure 3.9 yes Figure 3.8 A cross-sectional view of the shear pad location (the first and second circuit layers do not overlap at the vias).
[0053] Figure 3.10 yes Figure 3.8 A cross-sectional view of the shear pad location (the first and second circuit layers overlap at the vias).
[0054] Figure 3.11 yes Figure 3.9 Schematic diagram of the structure after soldering;
[0055] Figure 3.12 yes Figure 3.10 Schematic diagram of the structure after soldering;
[0056] Explanation of icon numbers:
[0057] 10-Adhesive, 1-First insulating film, 2-First circuit layer, 3-Intermediate insulating film, 31-Through hole, 32-Protective film, 4-Second circuit layer, 41-Metal foil, 5-Second insulating film, 51-Pad window, 6-Ink solder resist layer, 7-Scissors pad, 8-Pad, 9-Tin. Detailed Implementation
[0058] To make the objectives, technical solutions, and advantages of this utility model clearer, the embodiments of this utility model will be described in detail below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described below can be arbitrarily combined with each other.
[0059] The following provides many different implementation methods or examples for realizing the structure of this utility model.
[0060] See Figures 2.1-2.8 As shown, the first embodiment of this utility model provides a method for manufacturing a double-layer circuit board, including:
[0061] See details Figure 2.1 Prepare the first insulating film 1 with adhesive 10; see details. Figure 2.2 As shown, a wire is attached to the first insulating film 1 with adhesive 10 to form a first circuit layer 2; in other embodiments, a metal foil can also be attached to the first insulating film 1 with adhesive, and the unwanted metal is removed after die cutting to form the first circuit layer.
[0062] See details Figure 2.3 As shown, the middle insulating film 3 with adhesive on both sides is die-cut to form a through hole 31;
[0063] See details Figure 2.4 As shown, the metal foil is attached to the intermediate insulating film 3, then the metal foil is die-cut, and the unwanted metal is removed to form the second circuit layer 4;
[0064] See details Figure 2.5 As shown, the second insulating film 5 with adhesive on the top layer is die-cut to form a solder pad window 51;
[0065] See details Figure 2.6 As shown, a circuit board is formed by aligning and bonding a first insulating film 1 with a first circuit layer 2, an intermediate insulating film 3 with a second circuit layer 4, and a second insulating film 5 with a pad window 51, and then hot-pressing them together. According to the circuit design, the second circuit layer 4 is bonded to the first insulating film 1 at some or all of the through holes 31.
[0066] See details Figures 3.1-3.10 As shown, the second embodiment of this utility model also provides a method for manufacturing a double-layer circuit board, including:
[0067] See details Figure 3.1 As shown, a first insulating film 1 with adhesive 10 is prepared;
[0068] See details Figure 3.2 As shown, a wire is attached to the first insulating film 1 with adhesive 10 to form a first circuit layer 2; in other embodiments, a metal foil is attached to the first insulating film 1 with adhesive, and the unwanted metal is removed after die cutting to form the first circuit layer.
[0069] See details Figure 3.3 As shown, the middle insulating film 3 with adhesive on both sides is die-cut to form a through hole 31;
[0070] See details Figure 3.5 and Figure 3.6 As shown, a protective film 32 is attached to one side of the intermediate insulating film 3, and a metal foil 41 is attached to the other side. After hot pressing, the metal foil 41 on the intermediate insulating film 3 is etched using an etching method to obtain the second circuit layer 4. Then, the protective film is removed to obtain... Figure 3.4 The structure shown;
[0071] See details Figure 3.7 As shown, the first insulating film 1 with the first circuit layer 2 is aligned and bonded with the intermediate insulating film 3 with the second circuit layer 4, and then subjected to hot pressing, so that the second circuit layer 4 is bonded to the first insulating film 1 at some or all of the through holes 31.
[0072] See details Figure 3.8As shown, an ink solder resist layer 6 is fabricated on the second circuit layer.
[0073] See details Figure 2.7 , Figure 2.8 or Figure 3.9 , Figure 3.10 As shown, this embodiment of the utility model provides a double-layer circuit board, including a first insulating film 1, which is a back solder resist layer; and a first circuit layer 2, which is bonded to the first insulating film 1, specifically by adhesive 10. The first circuit layer 2 consists of circuits of uniform width (e.g., ...). Figure 2.2 As shown), the first circuit layer 2 can also be a circuit of varying widths. The first circuit layer 2 contains at least two main circuits > 1 meter in length. In this embodiment, the first circuit layer 2 has two main circuits. An intermediate insulating film 3 has through-holes 31 on it, through which the first circuit layer 2 is exposed. A second circuit layer 4 is bonded to the intermediate insulating film 3. At some or all of the through-holes 31, the circuits of the second circuit layer 4 are bonded to the first insulating film 1. The second circuit layer 4 partially blocks the intermediate insulating film 3 within the through-holes 31. Figure 2.7 , Figure 2.8 As shown, the intermediate insulating film 3 on the right side of the via 31 is shielded by the second circuit layer 4; the front solder mask layer is bonded to the second circuit layer 4, see details. Figure 2.7 and Figure 2.8 As shown, the front solder mask layer can be the second insulating film 5, which is bonded to the second circuit layer 4 and the intermediate insulating film 3 by adhesive 10; see details. Figure 3.9 and Figure 3.10 As shown, the front solder mask layer can also be an ink solder mask layer 6, attached to the second circuit layer 4 and the intermediate insulating film 3. The front solder mask layer has solder pad windows 51, some of which are located at the vias 31; some solder pad windows 51 are not located at the vias 31, and these latter solder pad windows can be used for soldering electronic components. Each solder pad window 51 at the via 31 exposes both the metal of the first circuit layer 2 and the metal of the second circuit layer 4, as shown. Figure 2.6 The scissor pad 7 in the via 31; or, the pad window 51 at the via 31, wherein part of the pad window exposes both the metal of the first circuit layer 2 and the metal of the second circuit layer 4, and part of the pad window exposes only the metal of the first circuit layer 2, such as Figure 2.6 Pad 8 in the circuit only exposes the metal of the first circuit layer 2.
[0074] In some embodiments of this utility model, the thickness of the first circuit layer 2 is greater than or equal to the thickness of the second circuit layer 4. The first circuit layer 2 serves as the main line for connecting the power supply to ensure sufficient current load. The second circuit layer 4 is mainly used to connect components (such as LED beads and resistors), which require a smaller current load. Reducing its thickness helps to save costs.
[0075] In some embodiments of this utility model, according to the circuit design, the second circuit layer 4 consists of multiple secondary circuits; in other embodiments, the second circuit layer 4 includes a main circuit and multiple secondary circuits.
[0076] In some embodiments of this utility model, at the via 31, both the first circuit layer 2 and the second circuit layer 4 are bonded to the first insulating film 1 and have formed pads. The metals of the first circuit layer 2 and the second circuit layer 4 are close to or in contact with each other (e.g., ...). Figure 2.7 or Figure 3.9 (as shown); in other embodiments, such as Figure 2.8 or Figure 3.10 As shown, the metal portion of the second circuit layer 4 overlaps on the first circuit layer 2.
[0077] In some embodiments of this invention, at the via 31, there is only a pad formed by the metal of the first circuit layer 2. This pad is used to solder one foot of the component or as a shear pad.
[0078] This utility model embodiment also provides an LED light strip, including the double-layer circuit board described in any of the above embodiments. Electronic components are soldered on the double-layer circuit board, and component leads are soldered to the pads at some or all of the through holes 31. The pads at the through holes where component leads are soldered are combined pads formed by the combination of the first circuit layer metal and the second circuit layer metal; or, the pads at the through holes where component leads are soldered are the first circuit layer metal; or, the pads at the through holes are only soldered with tin.
[0079] See details Figures 3.11-3.12 As shown, in this embodiment of the invention, the second circuit layer 4 is bonded to the intermediate insulating film 3. At some or all of the through holes 31, the circuits of the second circuit layer 4 are bonded to the first insulating film 1. The second circuit layer 4 partially blocks the intermediate insulating film 3 inside the through holes 31. Thus, when the circuit board is soldered, the intermediate insulating material blocked by the second circuit layer 4 will not repel the solder. The solder can flow smoothly to the two layers of circuit metal, reducing or avoiding solder voids and effectively improving the yield of the circuit board.
[0080] The embodiments of the present utility model have been described in detail above with reference to the accompanying drawings. However, the present utility model is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present utility model.
Claims
1. A double-layer circuit board, characterized in that, include: The first insulating film is the solder resist layer on the back side; The first circuit layer is bonded to the first insulating film. The first circuit layer consists of circuits of uniform width or circuits of inconsistent width. The first circuit layer contains at least two main circuits longer than 1 meter. An intermediate insulating film has a through hole on it, and a first circuit layer is exposed from the through hole at the through hole; The second circuit layer is bonded to the intermediate insulating film. At some or all of the vias, the circuits of the second circuit layer are bonded to the first insulating film. The second circuit layer partially blocks the intermediate insulating film inside the vias. A front solder mask layer is bonded to the second circuit layer. The front solder mask layer has pad windows, some of which are located at the vias. Each pad window at the via exposes both the metal of the first circuit layer and the metal of the second circuit layer; or, at the vias, some pad windows expose both the metal of the first circuit layer and the metal of the second circuit layer, while others expose only the metal of the first circuit layer.
2. A double-layer circuit board according to claim 1, characterized in that: The front solder resist layer is an insulating film or solder resist ink.
3. A double-layer circuit board according to claim 1, characterized in that: The thickness of the first circuit layer is greater than or equal to the thickness of the second circuit layer.
4. A double-layer circuit board according to claim 1, characterized in that: The second line layer consists of multiple secondary lines, or the second line layer includes a main line and multiple secondary lines.
5. A double-layer circuit board according to claim 1, characterized in that: At the via, both the first and second circuit layers are bonded to the first insulating film and have formed pads. The metals of the first and second circuit layers are close to each other or in contact from side to side, or the metal portion of the second circuit layer overlaps on the first circuit layer.
6. A double-layer circuit board according to claim 1, characterized in that: At the via, there is only a pad formed by the first line layer metal. This pad is used to solder one of the components or as a shear pad.
7. An LED light strip, characterized in that: The double-layer circuit board includes any one of claims 1-6, wherein electronic components are soldered on the double-layer circuit board, and component leads are soldered to the pads at some or all of the vias, and the pads at the vias with component leads are combined pads formed by a combination of the first circuit layer metal and the second circuit layer metal; or, the pads at the vias with component leads are the first circuit layer metal; or, the pads at the vias are only soldered with tin.