Application of laser welding and automation in the packaging of optical communication devices

1. Application background

In the industry, the traditional optical communication device packaging technology generally uses UV glue to bond and fix the device at the joint surface. First, the UV glue is applied to the device joint and then cured by ultraviolet light. This device connection method has many defects, such as limited curing depth; limited by the geometry of the device; the glue will not cure where the ultraviolet lamp cannot be irradiated. Both a glue device and an ultraviolet lamp are required to make the entire system mechanism more complicated. The most important thing is that when the device is actually used, due to factors such as heat, there will be a slight positional deviation of the upper and lower devices at the joint. , Causing the device coupling power value to be abnormal, the accuracy is reduced, the product quality is affected, and the production cycle is long and the efficiency is not high. The use of laser welding, a new type of welding technology, has the advantages of firm welding, minimal deformation, high precision, fast speed, and easy automatic control, making it one of the important means of optical communication device packaging technology. To this end, Chutian Laser independently developed a high-speed automatic coupling laser welding system, which is a system that integrates laser welding, its process technology, and automatic control technology.

2. Application of automation technology

2.1 Automatic device leveling technology

Through sensor control technology and electric arc pendulum mechanism, the adjustment ring (Z ring) of the optical communication device and the contact surface of the adapter are attached, that is, the device is automatically leveled. Generally, the gap between the two surfaces is required to be controlled between 0.01 and 0.03 mm.

According to the working mechanism of the coupling device and the requirements of the packaging process, the contact surface of the adjustment ring (Z ring) and the adapter must be flat to meet the requirements of the device. The adjusting ring (Z ring) is clamped on the upper chuck. The upper chuck can only move up and down without swinging. It is set as the reference surface. Therefore, if the contact surface of the adjusting ring (Z ring) and the adapter is required to be effectively flat, It is necessary for the adapter to automatically align with the contact surface of the adjusting ring (Z ring). The adapter is clamped on the lower chuck, and the lower chuck is installed on the sliding block. It can slide smoothly and is lifted up by the upper cylinder. When the Z axis moves downward, the adjusting ring (Z ring) compresses the adapter, and the lower chuck faces Down movement (the force of the Z axis is greater than the force of the upper cylinder, the upper cylinder is equipped with a precision pressure reducing valve, and the upper force can be adjusted through the precision pressure reducing valve). When the sliding block moves up and down, the high-precision displacement sensor detects the change of the displacement. At the same time, the electric arc pendulum mechanism swings according to the set motion track. When the displacement sensor detects the smallest displacement and the value does not change, the adjustment ring (Z ring) is attached to the adapter, the above is the automatic leveling mechanism of the device.

2.2 Device automatic coupling technology

We talked about the principle of device leveling in 2.1. Next, in accordance with the process sequence, the device is automatically coupled to find the light, that is, the target optical power value is found, and after the target optical power value is found, the device is automatically welded by laser to complete the packaging of the device.

For the special process requirements of welding optical communication devices, we adopt three-axis linkage precise control technology to find light according to the specified spiral coupling trajectory. Due to the extremely high precision of light finding, we use imported ultra-high-precision motion components to realize automatic coupling of the device to find light, that is, through the XY axis and Z axis difference compensation movement, and follow the spiral track to find the target optical power value of the upper and lower devices.

Automatic coupling control technology has the following characteristics:

• a. The coupling adopts high-performance and high-precision motion elements, combined with our self-developed advanced control software coupling algorithm, to achieve high coupling efficiency;
• b. Real-time display of the distribution curve of the leveling and coupling process. The purpose is to visually display the leveling and coupling process. Only when a standard, complete and smooth normal distribution curve appears, does the leveling or coupling reach the expected target value ；
• c. Operate the movement and debugging of each axis individually to facilitate the measurement of coupling parameters;
• d. Friendly software operation interface, different programs can be written according to the process of different devices (F-Basic programming, easy to learn) when automatic, and can be saved for customers to call next;
• e. Coupling parameter setting is simple and convenient, and the coupling mode is optional (coupling mode includes X-axis, Y-axis, Z-axis independent coupling, XY two-axis simultaneous coupling, XYZ three-axis simultaneous coupling), the coupling process is automatically completed;
• f. The welding head is automatically adjusted to automatically realize the welding of devices of different heights and diameters;
• g. CCD image real-time monitoring of each solder joint, convenient for customers to observe the situation of the solder joint in real time.

Whether it is device automatic leveling technology or device automatic coupling technology, it is realized through automatic control technology and related thinking strategies. In order to achieve the goal of automatic coupling and light finding, we carefully design this set of precision motion mechanism to achieve six-axis linkage. This set of mechanism also has a certain degree of flexibility, which can realize automatic coupling welding of different devices by quickly switching the corresponding welding jigs.

2.3 Coupling Algorithm Technology

According to the precise requirements of optical communication devices to find light, according to the movement mechanism of the device, it is necessary to study a movement trajectory, which can quickly find the target optical power value of the device coupling. For this reason, we adopt the algorithm of moving according to the spiral trajectory, starting from a certain point, the XY axis will make a difference compensation movement, follow the subdivided spiral movement trajectory, and move spirally from the inside to the outside until the target is found. Optical power value. Using this method can quickly and accurately find the coupled target optical power value

3. Application of laser welding technology

As a high-quality, high-precision, high-efficiency and high-speed welding method, laser welding has received increasing attention and applications. Due to the high energy density of the laser, the laser welding speed is fast, the welding depth is deep, and the heat affected zone is small, which can realize automatic precision welding.

3.1 laser welding machine

The laser packaging technology of optical communication devices has very high requirements on the energy distribution and energy stability of the welding machine, and the energy deviation value of the three-channel light (or the six-channel light) is ≤0.03J. To meet this requirement, we independently developed a special laser welding machine WF80.

3.2 Welding process research

• A. Welding point distribution: 3 guns can be welded at the same time, and the welding points of 9 positions in the circumferential direction (the distribution of penetration welding and flat welding are the same). In addition, the solder joint distribution can be changed by self-modifying the program.
• B. Flat welding and penetration welding can be done at the same time, and the diameter and penetration parameters of flat welding and penetration welding are required to be consistent.
• C. It has the repair welding function, that is, the defective welding can be directly repaired (the equipment has this function, but the use of optional can not be selected).
• D. After welding, the through rate of power deviation within 5% requires more than 90%, and the through rate requirement after the aging test does not change.
• E. The diameter of the solder joint is 0.4～0.7mm; the penetration depth of the solder joint is 0.3～0.6mm; the shearing force is ≥42Kg.
• F. Preliminarily judge the welding effect by adjusting the welding machine’s energy, welding gun incident angle, fine zoom and other process parameters, observing the brightness of the spark and listening to the sound of the laser hitting the device. Finally, by testing the size of the solder spot and the penetration depth of the device, it is judged whether the device meets the requirements.

4. Application analysis

The application of laser welding technology in the optical communication industry is actually not particularly novel. In this field, automatic coupling equipment has been put into the market in South Korea and Taiwan. However, due to the high price of their equipment, many domestic users have difficulty adapting to it. Communication devices have higher and higher requirements for welding equipment accuracy and laser welding technology, which requires equipment to be more precise, more stable, reliable and easy to operate. Therefore, imported equipment is also facing many challenges. Therefore, in order to meet market demand, based on the leading advantages of Han’s Laser Precision Welding Division in the field of laser welding and automatic control technology, we have developed a high-speed automatic coupling laser welding system.

From the perspective of welding processability, the application of laser welding technology in optical communication device packaging is relatively mature, but there is still a lot of room for improvement from automatic coupling technology to welding process. How can the coupling mechanism be simpler and more reliable, how can the fixture for holding the device be able to be quickly switched, accurately positioned, and how the coupling algorithm can be more concise, all these need to be constantly innovated and improved to improve the stability, reliability and machine of the entire system Debug operability. It is hoped that through the continuous improvement of research and development capabilities, advanced technology will be integrated into the research and development design to ensure the leading performance of the machine.