A laser welding process for multi-dimensional cross-oscillator interconnection between substrates

Abstract

The present invention discloses a laser welding process for multi-dimensional cross-oscillator interconnection between substrates, which accurately positions the workpiece to be welded through a five-axis linkage system, and determines the spray welding area and thickness of the spray solder paste; sprays the solder paste according to the spray welding area and thickness determined by S1, and checks the solder paste morphology; heats the solder paste through a laser to form a solder joint; and cleans the solder joint. Through the above-mentioned optimized laser welding process, the workpiece to be welded is accurately positioned through a five-axis linkage system, and the welding position, area, and thickness are designed in advance according to the requirements of the solder joint, thereby improving the welding efficiency. At the same time, the laser beam of the laser welding equipment can accurately locate the welding position, and the heat is relatively concentrated, avoiding thermal damage to the surrounding materials, achieving good consistency of the solder joints and a high pass rate.

Description

Technical Field

[0001] The present invention relates to the technical field of welding of vibrator interconnections, and in particular to a laser welding process for multi-dimensional cross-vibrator interconnections between substrates. Background Art

[0002] With the continuous development of electronic technology, the status of electronic countermeasure technology in military struggle is becoming increasingly important. As the operating frequency range of radar systems continues to expand, the requirements for antennas are also developing in the direction of ultra-wideband, high gain, and miniaturization. Radar countermeasure antennas are the core part of radar countermeasure systems. They are usually composed of antenna arrays of different frequency bands, and line source antennas are one of the typical forms. Each antenna array consists of a cross-assembly of different numbers of row line sources and column line sources, both of which are welded by microstrip boards and mounting angle pieces. In order to achieve electrical interconnection between microstrip boards, line sources need to be welded. This welding includes both welding between cross-microstrip boards and welding between connectors and microstrip board feeders. The solder joints between cross-microstrip boards are located in the vertical direction, while the solder joints between connectors and microstrip board feeders are located in the horizontal direction. The presence of multi-dimensional solder joints increases the difficulty of welding.

[0003] In most cases, manual welding is usually used to achieve the connection and transmission of electrical signals between microstrip boards. At present, antenna arrays are becoming more and more miniaturized and sophisticated. For example, the dual-polarized antenna in the XX radar product usually needs to use cross-polarization to eliminate interference in the two polarization directions in order to maintain the polarization purity of the antenna. The cross-polarization design makes manual welding more and more difficult. First, the narrow deep cavity structure between the boards limits the manual operation space, and the smaller the diameter of the soldering iron tip, the slower the heat conduction speed, and the more difficult it is to form a good solder joint. Secondly, the quality of manual welding mainly depends on the technical level of the welder. It takes a long time and high cost to train a qualified technician. In addition, the welding consistency of products completed by different technicians is poor, and multiple repairs are inevitable, which affects the production efficiency of the product. More repairs will also affect the long-term reliability of the product.

[0004] Laser welding is one of the important aspects of the application of laser material processing technology. It uses laser as a heat source to radiate the welding pad, and its characteristics are local rapid centralized heating and cooling. Traditional laser wire welding is a side-feeding method, in which the welding wire is fed into the focused spot, and then the laser beam heats and melts it and solidifies it to form a weld or welding point. In existing laser wire welding, since the light and wire are not coaxial, a slight change in the position between the two will cause coupling problems, thereby affecting the quality of the welding point. In addition, since the welding wire is only irradiated on one side of the laser, the material is easily heated unevenly, and high power is required for welding.

[0005] Therefore, in actual production, a new type of welding process is urgently needed to replace traditional manual welding and laser wire welding, which can meet the electronic interconnection requirements of deep cavities or small solder joints, and realize the refinement of the solder joint structure to obtain solder joints with good quality and high fatigue life. Summary of the invention

[0006] In order to solve the technical problems existing in the background technology, the present invention proposes a laser welding process for multi-dimensional cross-vibration element interconnection between substrates.

[0007] The present invention proposes a laser welding process for multi-dimensional cross-oscillator interconnection between substrates, comprising the following steps:

[0008] S1. Use the five-axis linkage system to accurately position the workpiece to be welded and determine the spraying area and thickness of the solder paste;

[0009] S2, spray solder paste according to the spray soldering area and thickness determined in S1, and check the solder paste shape;

[0010] S3, heating the solder paste by laser to form solder joints;

[0011] S4. Clean the solder joints.

[0012] Preferably, in S1, the workpiece to be welded is cleaned in advance.

[0013] Preferably, in S1, the spraying area and thickness of the solder paste are determined by, specifically, driving the focusing system to move through the electronically controlled servo system of the laser welding equipment to determine the welding position, while measuring the welding object distance through a laser rangefinder, and observing the welding position from a CCD monitoring system, and performing fine adjustments as needed.

[0014] Preferably, in S1, the spraying area of ​​the solder paste is determined according to the size of the solder pad and the height of the solder point.

[0015] Preferably, when the spray soldering area is located between the connector and the microstrip feed line, the thickness of the spray solder paste is h=d+h0, wherein h0 is the height of the inner conductor of the connector from the soldering pad, and d is the diameter of the inner conductor of the connector.

[0016] Preferably, when the soldering area is between the intersections of the line sources, the solder paste is sprayed on the pad.

[0017] Preferably, the solder paste is Sn96.5Ag3.0Cu0.5, Sn63Pb37 or Sn62Pb36Ag2.

[0018] Preferably, in S3 , welding is performed in a protective gas atmosphere.

[0019] Preferably, in S4, the workpiece is cleaned by placing it in a cleaning tank containing bromopropane.

[0020] In the present invention, the proposed laser welding process of multi-dimensional cross-oscillator interconnection between substrates uses a five-axis linkage system to accurately position the workpiece to be welded, and determines the spray welding area and thickness of the spray solder paste; sprays the solder paste according to the spray welding area and thickness determined by S1, and checks the solder paste morphology; heats the solder paste by laser to form solder joints; and cleans the solder joints. Through the above-mentioned optimized laser welding process, the workpiece to be welded is accurately positioned by a five-axis linkage system, and the welding position, area, and thickness are designed in advance according to the requirements of the solder joints to improve the welding efficiency. At the same time, the laser beam of the laser welding equipment can accurately locate the welding position, and the heat is relatively concentrated to avoid thermal damage to the surrounding materials, so as to achieve good consistency of the solder joints and a high pass rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of the structure of the welded antenna array surface in one implementation of a laser welding process for multi-dimensional cross-vibrator interconnection between substrates proposed by the present invention.

[0022] Figure 2 A schematic diagram of the structure of cross-element welding points in an implementation of a laser welding process for multi-dimensional cross-element interconnection between substrates proposed by the present invention. DETAILED DESCRIPTION

[0023] like Figure 1 and 2 As shown, Figure 1 This is a schematic diagram of the structure of the welded antenna array surface in one embodiment of a laser welding process for multi-dimensional cross-element interconnection between substrates proposed by the present invention. Figure 2 A schematic diagram of the structure of a cross-element solder joint in an embodiment of a laser welding process for multi-dimensional cross-element interconnection between substrates proposed by the present invention. 1 is an SMP connector, 2 is a column line source, 3 is a corner piece, 4 is a reflector, and 5 is a row line source.

[0024] The present invention proposes a laser welding process for multi-dimensional cross-oscillator interconnection between substrates, comprising the following steps:

[0025] S1. Use the five-axis linkage system to accurately position the workpiece to be welded and determine the spraying area and thickness of the solder paste;

[0026] Specifically, in S1, the part of the workpiece to be welded is cleaned in advance. In actual welding, the part of the microstrip board or connector to be welded can be cleaned manually or by equipment, and equipment cleaning includes ultrasonic cleaning, plasma cleaning, water cleaning and the like.

[0027] In a specific design, the spraying area and thickness of the spray solder paste are determined by driving the focusing system to move through the electronically controlled servo system of the laser welding equipment to determine the welding position, while measuring the welding object distance through a laser rangefinder, and observing the welding position from a CCD monitoring system, and making fine adjustments as needed. In a specific design, the position accuracy is preferably ≤±20um.

[0028] Furthermore, the soldering area of ​​the solder paste is determined according to the size of the pad and the height of the solder joint. In the specific selection of solder paste, the solder paste is selected from Sn96.5Ag3.0Cu0.5, Sn63Pb37 or Sn62Pb36Ag2. Sn96.5Ag3.0Cu0.5 is a typical lead-free solder with excellent physical properties and high temperature stability. Sn63Pb37 solder is the most widely used solder joint at present, with a low melting point (183°C) and good wettability to metals such as copper and nickel. The Ag in Sn62Pb36Ag2 solder can effectively improve the strength of the solder joint.

[0029] When the soldering area is located between the connector and the microstrip feeder, the thickness of the solder paste is h=d+h0, where h0 is the height of the inner conductor of the connector from the pad, and d is the diameter of the inner conductor of the connector. At this time, the solder paste has a rectangular parallelepiped structure.

[0030] When the spray soldering area is between the line sources, the solder paste is sprayed on the pad. At this time, the length and width of the solder paste are 0.1-0.4mm, and the thickness is 0.2mm-0.25mm.

[0031] S2, spray solder paste according to the spray soldering area and thickness determined in S1, and check the solder paste shape;

[0032] S3, heating the solder paste by laser to form solder joints;

[0033] Specifically, the high pulse energy generated by the laser is used to liquefy the alloy to form a welding spot to complete the welding. The laser light source is one of 1064nm, 355nm, and excimer lasers, with an output power of 1500mW to 2500mW. The laser energy output is 10%-25%, the time is 0.1-5s, and the spot diameter is 2-3.5mm.

[0034] In the specific welding process, welding is carried out in a protective gas atmosphere, wherein the protective gas can be nitrogen or argon.

[0035] S4. Clean the solder joints.

[0036] Specifically, the workpiece is placed in a cleaning tank containing bromopropane for cleaning.

[0037] Finally, the solder joints can be tested for mechanical strength and electrical properties.

[0038] In this embodiment, the proposed laser welding process for multi-dimensional cross-oscillator interconnection between substrates uses a five-axis linkage system to accurately position the workpiece to be welded, and determines the spraying area and thickness of the solder paste; sprays the solder paste according to the spraying area and thickness determined by S1, and checks the solder paste morphology; heats the solder paste by laser to form solder joints; and cleans the solder joints. Through the above-mentioned optimized laser welding process, the workpiece to be welded is accurately positioned through a five-axis linkage system, and the welding position, area, and thickness are designed in advance according to the requirements of the solder joints to improve the welding efficiency. At the same time, the laser beam of the laser welding equipment can accurately locate the welding position, and the heat is relatively concentrated to avoid thermal damage to the surrounding materials, so as to achieve good consistency of the solder joints and a high pass rate.

[0039] The present invention is further described below with reference to the accompanying drawings and specific examples:

[0040] Comparative Example 1:

[0041] For attachment Figure 1 The antenna array uses manual welding to weld multiple solder joints in different dimensional directions. The dimensions of a single row source are 120×15×0.5 (mm), and a single column source is 80×15×0.5 (mm). The row source and the column source are cross-assembled on the reflector, and the size of the square area formed is 8.9mm×8.9mm. The diameter of the conductor inside the connector is d=0.3mm, the length is l=1.5mm, and the size of the microstrip board feed pad is 1.5mm×2mm. The gap at the intersection of the line source is about 0.2mm wide.

[0042] The row line source 5 and the column line source 2 are welded by microstrip board and mounting angle piece 3, and then mounted on the transmitting board 4. The microstrip board is a multilayer board, and the welding position is grooved. The inner conductor is placed on the feed line of the microstrip board, and the laser provides heat source to complete the welding process. Figure 2 For the cross connection of row source and column source, the pad is slotted, and all welding areas and connectors are gold-plated. Before welding, the tooling and antenna array are installed to assist in the welding of the connector and the antenna mounting plate.

[0043] First, apply RMA type flux to the inner conductor of the connector and the position to be welded on the microstrip board. Due to the small deep cavity, a thinner soldering iron tip is used and soldered at a certain angle. The solder used is a solder wire composed of Sn62Pb36Ag2, and the temperature of the hot plate is set to 380℃. For the welding of the cross-microstrip board, make sure that the solder fills the gap at the intersection. After each solder joint is welded, it is cleaned with acetone or alcohol, and then a 40x magnifying glass is used for appearance inspection. For an antenna array composed of 18 row line sources and 36 column line sources cross-assembled, the manual welding time is about 1.5h. After the solder joint inspection is qualified, it is handed over to the telecommunications designer for electrical performance testing. The results show that the qualified rate of the product is about 60%, and the solder joints at the cross-oscillator have different morphologies, with lengths and widths ranging from 0.4mm-1.0mm. Unqualified products need to be repaired.

[0044] Embodiment 1

[0045] As shown in the figure, the operation process of a laser welding process of multi-dimensional interconnected cross-oscillators is as follows.

[0046] The printing range of solder paste is determined according to the size of the pad and the height of the solder joint, and the laser welding process is carried out in a nitrogen atmosphere.

[0047] In the first embodiment, the diameter of the inner conductor of the connector is d=0.2mm, the length is l=1.5mm, the size of the pad of the microstrip board feeder is 1.5mm×2mm, and the height of the inner conductor of the connector from the pad is h0=0.1mm. Therefore, the height of the solder joint is h=0.1+0.2=0.3mm. After the tooling is installed, the solder paste is sprayed on the pad of the microstrip board through an automatic solder paste spraying device, and the printing thickness is 0.3mm. The selected solder paste is Sn62Pb36Ag2. The solder paste spraying system sprays the solder paste on the pad between the boards or the position to be welded between the connector and the antenna feeder. After the printing is completed, the thickness and shape of the solder paste are checked by a solder paste thickness gauge. During welding, the laser heats the position to be welded and liquefies the alloy to achieve interconnection between microstrip boards and between connectors and microstrip boards. At this time, the laser energy output is 18%, the time is 3s, and the spot diameter at the focus is about 3mm.

[0048] In Example 1, the solder paste printed on the pads between the intersecting boards has a thickness of 0.2 mm, a length and a width of 0.2 mm, and the solder paste is heated by laser, the energy output of the laser is 32%, the time is 50 ms, and the spot diameter is 1.5 mm. The laser heat source parameters during welding are energy output 20% and time 1 s.

[0049] After the welding of one welding spot is completed, the equipment's robotic arm and clamping arm will operate in sequence according to the pre-set program to complete the welding of all welding spots on the array surface.

[0050] After welding, the antenna array is placed in a water cleaning device for cleaning, and the cleaning liquid is bromopropane. After that, appearance inspection and electrical performance test are carried out. The solder joints are required to have good wetting, no defects such as pull tips and shrinkage holes, the solder is spread evenly and continuously on the solder joint surface, the contact angle is less than 30°-50°, and the electrical standing wave is <1.8. In Example 1, the entire antenna array has a total of 648 antenna units, and the total welding time is about 0.9h (including cleaning time). The height of the connector solder joints is generally about 0.3mm, and the length and width m of the solder joints between the cross-vibrators are about 0.5mm, and the solder joints have good consistency. After external inspection, the electrical inspection results show that the qualified rate is about 95%.

[0051] Embodiment 2

[0052] Different from the first embodiment, the dual connector in the second embodiment has two inner conductors, which are connected to the feed lines of the column source and the row source respectively. The diameter of the inner conductor of the connector is d = 0.3 mm, and the length is l = 1.5 mm. In addition, the solder paste used in the second embodiment is Sn63Pb37. The specific operation process and parameters are as follows:

[0053] First, use an alcohol cotton ball to clean the inner conductor of the connector and the pad waiting for welding, leaving no excess. The size of the microstrip board feed pad is 1.5mm×2mm, and the height of the connector inner conductor from the pad is h0=0.1mm. Therefore, the height of the solder joint is h=0.1+0.3=0.4mm, and the printing thickness of the solder paste is 0.4mm. The pad parameters at the intersection of the line source are the same as those in Example 1. After the printing is completed, check the thickness and morphology of the solder paste. The laser heats the position to be welded and liquefies the alloy. The laser energy output is 20%, the time is 2.5s, and the spot diameter at the focus is about 3mm. According to the pre-set procedure, the welding of all solder joints on the array surface is completed in sequence. After welding, the antenna can be cleaned with ultrasound. There are 648 antenna units, and the total welding time is about 1.3h (including cleaning time), and the solder joint morphology is consistent. After external inspection, the electrical test results show that the qualified rate is about 96%.

[0054] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A laser welding process for multi-dimensional cross-oscillator interconnection between substrates, characterized in that: The following steps are involved: S1. Use the five-axis linkage system to accurately position the workpiece to be welded and determine the spraying area and thickness of the solder paste; S2, spray solder paste according to the spray soldering area and thickness determined in S1, and check the solder paste shape; S3, heating the solder paste by laser to form solder joints; S4, cleaning the solder joints; Determining the spraying area and thickness of the spray solder paste is specifically to drive the focusing system to move through the electronic control servo system of the laser welding equipment to determine the welding position, and at the same time measure the welding object distance through the laser rangefinder, and observe the welding position through the CCD monitoring system, and make fine adjustments as needed; In S1, the solder paste spraying area is determined according to the size of the solder pad and the height of the solder joint; When the spray welding area is between the line sources, the solder paste is sprayed on the pad, and the length and width of the solder paste are 0.1-0.4mm, and the thickness is 0.2mm-0.25mm; When the spray soldering area is located between the connector and the microstrip feeder, the solder paste is sprayed on the position to be soldered between the connector and the antenna feeder, and the thickness of the spray solder paste is h=d+h0, where h0 is the height of the inner conductor of the connector from the pad, and d is the diameter of the inner conductor of the connector.

2. The laser welding process for multi-dimensional cross-oscillator interconnection between substrates according to claim 1 is characterized in that: In S1, the portion of the workpiece to be welded is cleaned in advance.

3. The laser welding process for multi-dimensional cross-oscillator interconnection between substrates according to claim 1 is characterized in that: The solder paste is Sn96.5Ag3.0Cu0.5, Sn63Pb37 or Sn62Pb36Ag2.

4. The laser welding process for multi-dimensional cross-oscillator interconnection between substrates according to claim 1 is characterized in that: In S3 , welding is performed in a protective gas atmosphere.

5. The laser welding process for multi-dimensional cross-oscillator interconnection between substrates according to claim 1 is characterized in that: In S4, the workpiece is cleaned by placing it in a cleaning tank containing bromopropane.

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