DCDC converter and manufacturing method thereof

Abstract

The invention discloses a DCDC converter and a manufacturing method thereof, which comprises a welding processing link of a patch transformer and a circuit PCB (Printed Circuit Board), and specifically comprises the following steps of: preparing materials, providing a patch type magnetic core, winding a coil on a winding post of the magnetic core, manufacturing the patch transformer, the end part of the coil is welded on the metal electrode of the magnetic core in a spot welding or thermocompression welding manner; in the laser cleaning step, laser is used for conducting laser ablation on the end portion of the coil and the surface of the metal electrode of the magnetic core at the same time, insulating film residues on the wire end of the coil and insulating film residues on the metal electrode of the magnetic core are ablated away, and the end portion of the wire end of the coil and the surface of the metal electrode of the magnetic core are clean; and a welding step: enabling the electric connecting piece to be in physical contact with the end part of the coil, the magnetic core metal electrode and the bonding pad of the PCB through a ball mounting process or a low-temperature tin immersion process, and forming interconnected welding spots. According to the invention, the electric connecting piece is added to be welded with the external circuit electrode, so that the weldability of the inductive device is improved.

Description

Technical Field

[0001] The invention belongs to the field of micro-power DCDC converters of switching power supplies, and in particular relates to a DCDC converter including an inductive device and a manufacturing method thereof. Background Art

[0002] As a passive component, inductive devices are widely used in the micro-power switching power supply industry. With the development of miniaturization of electronic products, inductive devices are also constantly upgraded and iterated to reduce the size of the device itself. In order to reduce the size of the inductive device as much as possible, a winding type chip inductive device with a drum-shaped magnetic core as the main body has appeared on the market. The coil is wound on the magnetic core and directly welded to the electrode on the magnetic core. Then the entire inductive device is mounted on the PCB circuit board.

[0003] However, the current micro-power DCDC converter with a drum-shaped magnetic core as the main body of the winding type chip inductive device still has the following shortcomings: The ends and tails of the conductive coil need to be welded to the metal electrodes of the magnetic core. The conductive coil itself contains an insulating film. During the welding process, the insulating film will remain on the metal electrode, reducing the contact area between the metal electrode of the magnetic core and the PCB pad, affecting the welding strength and reliability. In severe cases, a "cold weld" will be formed, and the metal electrode of the magnetic core will have no electrical connection with the PCB.

[0004] In order to solve the above-mentioned deficiencies, the industry has also proposed a solution, that is, before the end of the conductive coil is welded to the metal electrode of the magnetic core, the insulating film of the conductive coil is processed, and the method usually adopted is laser peeling, and then the wire head or wire tail after the insulating film is removed is welded to the metal electrode of the magnetic core by pulse spot welding or hot pressing welding; this method can solve the problem of solder resistance caused by the residual insulating film, but the energy of pulse welding or hot pressing welding is very large, and the tin layer on the surface of the metal electrode will be oxidized. The oxidized electrode will also cause poor welding with the PCB, such as solder resistance or cold welding or insufficient welding strength; at the same time, the enameled wire end is laser peeled in advance, and the peeling position and tolerance are difficult to control, which may easily lead to the peeling position and tolerance deviation, resulting in insufficient pressure resistance distance between the exposed end of the first coil conductor and the second coil, resulting in poor pressure resistance or reduced pressure resistance reliability.

[0005] In view of the above shortcomings, the industry also has an optimized solution, which is to add tin to the metal electrode by dipping it in a high-temperature tin furnace with a temperature greater than or equal to 400°C after the wire is welded at the end of the magnetic core, so as to remove the residual insulating paint and re-attach a new layer of solder to the metal electrode, thereby avoiding welding reliability problems caused by surface oxidation of the electrode; however, this solution also has hidden dangers. On the one hand, the magnetic core is a sintered body. Under the instantaneous high temperature of about 400°C when dipping it in a tin furnace, it is very likely to directly break or produce dark cracks, thereby affecting the magnetic conductivity of the magnetic core body; on the other hand The winding pole of this drum-shaped magnetic core is arranged in parallel with the metal electrode. The length of the patch inductive device is between 5.5mm and 6.3mm, the width is between 2.9mm and 3.5mm, and the height is ≤2.4mm. In the small-volume inductive device, the metal electrode and the wire coil are very close (the distance between them is only about 0.5mm). The tinning process is difficult to control and will not directly immerse the coil. The coil insulation film itself is not resistant to high temperature. It is very easy to cause the insulation film to be damaged or the life to be reduced when immersed in a high-temperature tin furnace of about 400℃, resulting in performance failure of the conductive coil. Summary of the invention

[0006] The present invention aims to overcome the above defects in the prior art and provide a DCDC converter and a manufacturing method thereof to improve the solderability problem of the metal electrodes of the inductive device.

[0007] In order to achieve the above object, the present invention adopts the following technical solution: A manufacturing method of a DC-DC converter is applicable to a patch transformer in which a winding post of a magnetic core is arranged in parallel with a metal electrode, and includes a welding process link between the patch transformer and a circuit PCB board, specifically including the following steps: a material preparation step, providing a patch magnetic core, winding a coil on the winding post of the magnetic core to make a patch transformer, and welding the end of the coil to the metal electrode of the magnetic core by spot welding or hot pressing welding; a laser cleaning step, using a laser to simultaneously laser ablate the end of the coil and the surface of the metal electrode of the magnetic core, ablate the insulating film residue on the coil wire end and the insulating film residue on the metal electrode of the magnetic core, so that the end of the coil wire end and the surface of the metal electrode of the magnetic core are clean; a welding step, through a ball planting process or a low-temperature tinning process, the electrical connector is physically contacted with the coil end, the metal electrode of the magnetic core and the soldering pad of the circuit PCB board to form an interconnection solder joint, and after the interconnection solder joint is cooled, the welding of the patch transformer and the circuit PCB board is completed, wherein the low temperature in the low-temperature tinning process means that the tin furnace temperature is less than 350° C.

[0008] Preferably, in the laser cleaning step, the laser ablation power of the insulating film of the coil does not exceed 5W.

[0009] Preferably, in the material preparation step, the coil is wound with enameled wire or three-layer insulated wire, and the insulation film of the coil has a temperature resistance between 130°C and 240°C.

[0010] Preferably, in the electrical connection step, the electrical connector is a solder body, and the melting temperature of the solder body is less than or equal to 400°C.

[0011] Preferably, the circuit PCB board is a carrier board on which electronic components of a DCDC converter circuit with a power of 3 W or less are installed.

[0012] The present invention also provides a DCDC converter, comprising a magnetic core in which a winding column and a metal electrode are arranged in parallel, which is manufactured by the manufacturing method of the above-mentioned DCDC converter, and comprises a transformer, an electrical connector and a circuit PCB board. The electrical connector is in a local ellipsoid shape or a film shape and wraps the coil end of the transformer, and is in physical contact with the coil end and the metal electrode of the magnetic core and the pad of the circuit PCB board to form an interconnected solder joint. The operating power of the transformer is ≤3W.

[0013] Preferably, the input voltage of the transformer is between 2V-6V, the output voltage is between 2V-6V, and the input-output isolation withstand voltage is 2500VDC.

[0014] Preferably, the transformer of the DCDC converter has a length between 5.5 mm and 6.3 mm, a width between 2.9 mm and 3.5 mm, and a height ≤2.4 mm.

[0015] Preferably, the packaging structure of the DCDC converter is a surface mount package, a SIP package or a DIP package.

[0016] The present invention further provides a DCDC converter, comprising a surface-mount transformer and a circuit PCB board, wherein the transformer is composed of a magnetic core and a coil wound thereon, the coil of the transformer is wound by enameled wire or three-layer insulated wire, the magnetic core of the transformer has a winding column and two ends, the ends of the magnetic core are provided with metal electrodes, the winding column of the magnetic core and the metal electrode are arranged between the two ends in parallel, and also comprises an electrical connector, the electrical connector is a solder body, the components of the electrical connector solder body include tin, and are arranged on the metal electrode of the magnetic core, wrapping the coil end of the transformer in a partial ellipsoid shape or a film shape, and physically contacting the coil end and the metal electrode of the magnetic core and the pad of the circuit PCB board to form an interconnected solder joint, and the working power of the transformer is ≤3W.

[0017] The DCDC converter and the manufacturing method thereof of the present invention have the following beneficial effects: 1. The method of laser cleaning before soldering the interconnection solder joints, coupled with the use of a new ellipsoidal solder body, can avoid solder resistance or "false solder joints" caused by residual insulating film at the interconnection solder joints at the metal electrodes of the magnetic core; the surface of the new solder body is bright, which also improves the reliability of welding with the circuit PCB board pads; 2. By adding electrical connectors to solder with the circuit PCB pads or external circuit electrodes, the solder body is supplemented based on this technology, and the temperature is lower than 400°C. When low-temperature tinning is used, the tin furnace temperature can be as low as 260-320°C, which will not affect the insulation performance and reliability of the coil body; there is no destructive effect on the core body and the conductive coil body, thereby ensuring that the performance of the inductive device is not affected by high temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the overall structure of the inductive device of the DCDC converter of the present invention assembled on the PCB; Figure 2 It is a schematic side view of the overall structure of the inductive device of the DCDC converter of the present invention assembled on the PCB; Figure 3 It is a side structural schematic diagram of the inductive device of the DCDC converter of the present invention; Figure 4 The present invention is a flow chart of the inductive device welding processing method of the DCDC converter.

[0019] Among them, 10 is a magnetic conductor, 101 is a winding pole, 102 is an end of the magnetic conductor, 103 is a metal electrode at the end of the magnetic conductor, 20 is a coil, 201 is an end of the coil, 30 is an electrical connector, 40 is a circuit PCB board, 401 is a pad on the circuit PCB board, and 50 is an inductive device. DETAILED DESCRIPTION

[0020] Aiming at the current problem of insufficient solderability in the direct winding welding process of inductive devices such as the patch core of a DCDC converter, the present invention provides an inductive device, comprising: a magnetic conductor, the magnetic conductor is provided with a winding post and two ends, the ends are provided with metal electrodes, the winding post and the metal electrode are arranged in parallel between the two ends; a conductive coil, the conductive coil is wound on the winding post of the magnetic conductor, the end of the conductive coil is arranged on the metal electrode at the end of the magnetic conductor and forms physical contact with the metal electrode; an electrical connector is a solder body, which wraps the end of the conductive coil in a local ellipsoidal or film shape, is arranged on the metal electrode of the magnetic conductor, and is used to form physical contact with the end of the conductive coil and the metal electrode of the magnetic conductor and the circuit PCB board to form an interconnected solder joint. Preferably, the magnetic conductor includes at least two metal electrodes, which are arranged on the same end or on different ends. The conductive coil also includes a metal conductive wire core and an insulating film; the insulating film covers and insulates the metal conductive wire core. The cross-section of the conductive wire core of the coil is circular or square, and the insulating film of the conductive coil has a temperature resistance between 130°C and 240°C. The electrical connector includes a solder body, the solder body includes tin, and the melting temperature of the solder body is ≤400°C.

[0021] The present invention and its beneficial effects will be further described in detail below in conjunction with specific implementations and the accompanying drawings, but the specific implementations of the present invention are not limited thereto.

[0022] See also Figures 1 to 3 The structure of an inductive device 50 of the DCDC converter of the present invention comprises a magnetic conductor 10, wherein the magnetic conductor 10 comprises a winding post 101, an end 102, and a metal electrode 103 on the end; a coil 20 is wound on the winding post 101 of the magnetic conductor 10, and the end 201 of the coil 20 is 201, and the end 201 of the coil 20 is arranged on the metal electrode 103 of the magnetic conductor 10; then, an electrical connector 30 is arranged above the end 201 of the coil 20, and the electrical connector 30 is partially ellipsoidal, and the electrical connector 30 is in physical contact with the end 201 of the coil 20, the metal electrode 103 of the magnetic conductor 10, and the pad 401 of the circuit PCB board 40 to form an interconnected solder joint of electrical connection. The coil 20 is a conductive coil, which is wound by enameled wire or three-layer insulated wire, and the insulation film of the coil has a temperature resistance between 130°C and 240°C.

[0023] See also Figure 2 , is a side view of the overall structure of the welding connection between the inductive device and the circuit PCB board. Figure 2 It can be seen that the electrical connection between the inductive device and the pad 401 of the circuit PCB board 40 is achieved through the electrical connector 30. The metal electrode 103 of the magnetic core body of the inductive device and the end 201 of the coil will not be in direct contact with the PCB pad 401, so there is no need to worry about the oxidation solder mask or insulation film residue of the metal electrode causing welding reliability problems. Preferably, the magnetic conductor 10 is a magnetic core, the electrical connector 30 is a solder body, including but not limited to lead-free tin or tin beads used for welding, and the inductive device 50 is a transformer. The circuit PCB board 40 is a carrier board for electronic components of a DCDC converter circuit with a power of 3W or less. Preferably, the inductive device 50 is a transformer. The DCDC converter can also be called a DCDC converter.

[0024] See also Figure 4 , is a flow chart of the inductive device welding processing method of the DCDC converter of the present invention. The manufacturing method of the DCDC converter of the present invention includes the welding processing link of the patch transformer and the circuit PCB board, and specifically includes the following processing process: Step 1: Provide a magnetic core, and wind a coil on the winding column of the magnetic core to make a chip transformer; Step 2: Weld the ends of the transformer coil to the metal electrodes of the magnetic core by pulse spot welding or hot pressing welding; Step 3: Use laser to ablate the ends of the coil and the surface of the metal electrode at the same time, ablate the insulating film residue on the end of the coil wire and the insulating film residue on the metal electrode, so that the end of the coil wire and the surface of the metal electrode of the magnetic core are clean; Step 4: Place the electrical connector 30 on the end of the coil and the metal electrode. Specifically, a ball planting process or a low-temperature tinning process or other welding process can be used to make the tin physically contact with the coil end, the core metal electrode and the pad of the circuit PCB board to form interconnection solder joints. After the interconnection solder joints are cooled, the welding of the chip transformer and the circuit PCB board is completed. The low temperature in the low-temperature tinning process means that the tin furnace temperature is less than 350°C.

[0025] Preferably, in step one, the transformer coil is wound by enameled wire or three-layer insulated wire, and the temperature resistance of the coil is between 120°C and 240°C.

[0026] Preferably, the power of laser ablation in step three does not exceed 3W.

[0027] Preferably, the insulating film of the laser ablated coil in step three has a temperature resistance between 130° C. and 240° C.

[0028] Through the above manufacturing method of the DCDC converter, in step three, the metal electrode is accurately positioned by laser ablation, and the insulating film of the wire end part of the coil located on the metal electrode is removed, and the surface oxide layer of the metal electrode itself is also removed, so as to realize the clean treatment of all metal surfaces in the welding area of ​​the interconnection solder joint, and the whole process only treats the surface of the metal electrode, and will not cause damage to the coil insulation layer outside the metal electrode, thereby ensuring the reliability of the insulation film performance of the coil. Secondly, the laser ablation power does not exceed 3W, the energy is low, and the temperature generated instantly is relatively low, which does not affect the mechanical strength and electrical performance of the magnetic core body. In step four, in the process of supplementing the electrical connector, the transformer coil insulation film is not immersed in a high-temperature tin furnace, and the magnetic core body is not immersed in high temperature. It is a relatively low-temperature welding process, so that the inductive device can avoid the residual solder resistance of the insulating film, welding thermal oxidation and magnetic core fragmentation caused by high-temperature tinning while supplementing the new coating, thereby improving the welding reliability of the DCDC converter power supply product, and avoiding the degradation or failure of the performance of the inductive device itself caused by high temperature.

[0029] The above are only preferred embodiments of the invention. It should be noted that the above preferred embodiments should not be regarded as limiting the present invention, and its protection scope should be based on the scope defined by the claims. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the spirit and scope of the application of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for manufacturing a DCDC converter, which is suitable for a patch transformer in which the winding pole of the magnetic core is arranged in parallel with the metal electrode, includes a welding process between the patch transformer and the circuit PCB board, and specifically includes the following steps: The material preparation step includes providing a chip-type magnetic core, winding a coil on a winding column of the magnetic core to make a chip transformer, and welding the end of the coil to a metal electrode of the magnetic core by spot welding or hot pressing; Laser cleaning step, using laser to simultaneously ablate the ends of the coil and the metal electrode surface of the magnetic core, ablating the insulating film residue on the coil wire ends and the insulating film residue on the metal electrode of the magnetic core, so that the ends of the coil wire ends and the metal electrode surface of the magnetic core are clean; The welding step is to make the electrical connector physically contact with the coil end, the core metal electrode and the pad of the circuit PCB board through a ball planting process or a low-temperature tinning process to form interconnection solder joints. After the interconnection solder joints are cooled, the soldering of the SMD transformer and the circuit PCB board is completed, wherein: The low temperature in the low temperature tinning process means that the temperature of the tin furnace is less than 350°C.

2. The method for manufacturing a DCDC converter according to claim 1, characterized in that: In the laser cleaning step, the laser ablation power of the insulating film of the coil does not exceed 5W.

3. The method for manufacturing a DCDC converter according to claim 1, characterized in that: In the material preparation step, the coil is wound with enameled wire or three-layer insulated wire, and the insulation film of the coil has a temperature resistance between 130°C and 240°C.

4. The method for manufacturing a DCDC converter according to claim 1, characterized in that: In the welding step, the electrical connector is a solder body, and the melting temperature of the solder body is less than or equal to 400°C.

5. The method for manufacturing a DCDC converter according to claim 1, characterized in that: The circuit PCB board is a carrier board on which electronic components of a DCDC converter circuit with a power of 3W or less are installed.

6. A DCDC converter, comprising a magnetic core with winding posts and metal electrodes arranged in parallel, manufactured by the manufacturing method of a DCDC converter according to any one of claims 1 to 5, characterized in that: The invention comprises a transformer, an electrical connector and a circuit PCB board. The electrical connector is in a partial ellipsoid shape or a film shape and wraps around the coil end of the transformer. The electrical connector is in physical contact with the coil end and the metal electrode of the magnetic core and the pad of the circuit PCB board to form interconnected solder joints. The working power of the transformer is ≤3W.

7. The DCDC converter according to claim 6, characterized in that: The input voltage of the transformer is between 2V-6V, the output voltage is between 2V-6V, and the input-output isolation withstand voltage is 2500VDC.

8. The DCDC converter according to claim 6, characterized in that: The transformer of the DCDC converter has a length between 5.5 mm and 6.3 mm, a width between 2.9 mm and 3.5 mm, and a height of ≤2.4 mm.

9. The DCDC converter according to claim 6, characterized in that: The packaging structure of the DCDC converter is a surface mount package, a SIP package or a DIP package.

10. A DCDC converter, comprising a SMD transformer and a circuit PCB board, wherein the transformer is composed of a magnetic core and a coil wound thereon, wherein the coil of the transformer is wound by enameled wire or three-layer insulated wire, wherein the magnetic core of the transformer has a winding post and two ends, wherein the ends of the magnetic core are provided with metal electrodes, and the winding post of the magnetic core is arranged parallel to the metal electrode between the two ends, wherein: It also includes an electrical connector, which is a solder body. The component of the electrical connector solder body includes tin, which is arranged on the metal electrode of the magnetic core, wraps the coil end of the transformer in a partial ellipsoid or film shape, and physically contacts the coil end and the metal electrode of the magnetic core and the solder pad of the circuit PCB board to form an interconnected solder joint. The working power of the transformer is ≤3W.

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