A laser eutectic method of an optical module

Abstract

The application provides a laser eutectic method of an optical module, comprising the following processes: first, a suction nozzle is used to pick up a laser chip to a substrate, the suction nozzle maintains contact with the laser chip for 1-2 seconds after the eutectic solder is heated to a temperature T, wherein T is not less than the melting point temperature of the eutectic solder; then, the pressure of the suction nozzle on the laser chip is removed, and the eutectic solder is continuously heated at the temperature T to completely melt into a liquid state and is maintained for 2-10 seconds. After the eutectic solder reaches the melting temperature, the suction nozzle is temporarily in contact with the laser chip and then leaves, the cooling effect of the low-temperature suction nozzle on the laser chip is eliminated, the solder at the bottom of the laser chip is smoothly melted, and the eutectic welding is smoothly completed; meanwhile, since the suction nozzle leaves the laser chip, the pressure on the upper surface of the laser chip is removed, when the eutectic solder is melted, the overflowed eutectic solder can reflow to the bottom of the laser chip, and thus it is ensured that there is enough solder at the bottom of the laser to complete the welding.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical module processing, and particularly relates to a laser eutectic method of an optical module. BACKGROUND

[0002] The main function of an optical module is to convert input electrical signals into optical signals and output, and convert received optical signals into electrical signals to complete signal transmission. The transmitting end of the optical module has a very important optical chip laser. The laser is usually eutectically welded to an aluminum nitride substrate by gold-tin solder, and then bonded to the shell of the optical module, and then connected to the PCB of the optical module through gold wire bonding. We usually call the finished product of eutectically welding the laser to the aluminum nitride substrate as COC (Chip On Carrier), as shown in Figure 1 The volume of the laser used for optical communication is very small, usually less than 300um*300um, and the power consumption of the laser itself is relatively large, usually more than 0.1W. The performance of the laser itself will deteriorate seriously at high temperature, so the quality of eutectically welding the laser to the aluminum nitride substrate directly affects the performance of the laser. If the laser is not well welded to the aluminum nitride substrate, it will directly affect the heat dissipation of the laser, and also affect the connection reliability of the laser and the aluminum nitride substrate. Poor welding will cause the laser to fall off during use, thereby causing reliability problems.

[0003] The existing laser eutectic process is as follows: first, the eutectic heating table is warmed to an initial temperature, the aluminum nitride substrate is grabbed by the suction nozzle to the heating table, then the laser is grabbed by the suction nozzle to the heating table, and the suction nozzle is kept in contact with the upper surface of the laser to fix the position of the laser. The contact pressure of the suction nozzle is 10g, then the heating table is warmed to 320 degrees and maintained for 10s (the melting point of gold-tin solder is 280 degrees), at this time the suction nozzle still keeps contact with the laser; finally, the heating table is cooled to the initial temperature, the COC finished product is grabbed by the suction nozzle to the material box to complete a COC eutectic. The COC eutectic temperature curve using this eutectic method is shown in Figure 2 During the entire eutectic process, the suction nozzle maintains contact with the laser, and the contact pressure is about 10g.

[0004] The existing laser eutectic welding method has the following problems:

[0005] (1) Since the nozzle is usually made of metal material and the laser chip is very small in size and the nozzle has no heating function, when the eutectic soldering is performed, although the aluminum nitride substrate is heated to a temperature of 320 degrees, which is higher than the melting point of the gold-tin solder, the nozzle itself is not heated, and the cooling effect of the nozzle on the laser chip is very obvious. Even if the temperature of the eutectic soldering is further increased, the temperature of the solder at the bottom of the laser chip usually cannot reach the melting point of the solder, thereby resulting in poor eutectic soldering quality or even eutectic soldering failure.

[0006] (2) Since the nozzle always contacts the laser chip and a pressure of 10 g is applied to the laser chip, due to the very small area of the laser chip, the local pressure at the bottom of the laser chip is very large. When the solder is melted, the solder at the bottom of the laser chip is prone to overflow, thereby resulting in the problems of no solder or less solder at the bottom of the laser chip, which also leads to poor soldering or even soldering failure. SUMMARY

[0007] The purpose of the present application is to provide a laser eutectic soldering method of an optical module, which can at least solve some defects in the prior art.

[0008] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0009] A laser eutectic soldering method of an optical module, comprising the following processes:

[0010] The nozzle is used to grab the laser chip to the substrate with pre-positioned eutectic solder, and the nozzle maintains contact with the laser chip for 1-2 seconds after the eutectic solder is heated to a temperature T, wherein T is not less than the melting point temperature of the eutectic solder;

[0011] The vacuum of the nozzle is closed, the pressure of the nozzle on the laser chip is removed, and the eutectic solder is continuously heated at the temperature T until the eutectic solder is completely melted into a liquid state and maintained for 2-10 seconds.

[0012] Further, the laser eutectic soldering method of the optical module specifically comprises the following steps:

[0013] 1) Preheat the heating table;

[0014] 2) The nozzle of the automatic patch eutectic soldering machine is used to grab the substrate with pre-positioned eutectic solder to the preheated heating table;

[0015] 3) The nozzle of the automatic patch eutectic soldering machine is used to grab the laser chip to the corresponding position on the substrate, and the position of the laser chip is fixed by keeping the nozzle in contact with the upper surface of the laser chip;

[0016] 4) The heating table is heated to a temperature T and maintained for 1-2 seconds, during which the nozzle is kept in contact with the laser chip;

[0017] 5) the heating stage continues to maintain the temperature T, the suction nozzle vacuum is closed, and the suction nozzle is moved away from the upper surface of the laser chip until the eutectic solder is completely melted into liquid state and maintained for 2-10 seconds;

[0018] 6) the heating stage is cooled, and the laser chip is fixed.

[0019] Further, the eutectic solder adopts gold-tin solder.

[0020] Further, the preheating temperature of the heating stage is normal temperature to 260°C.

[0021] Further, the preheating temperature of the heating stage is 240°C.

[0022] Further, the contact pressure of the suction nozzle and the laser chip in step 3) is 10g.

[0023] Further, the heating temperature T of the heating stage in step 4) and step 5) is 320°C.

[0024] Further, the temperature of the heating stage in step 6) is cooled to 240°C.

[0025] Compared with the prior art, the beneficial effects of the present application are:

[0026] In the laser eutectic method of the light module provided by the present application, after the eutectic solder reaches the melting temperature, the suction nozzle is briefly contacted with the laser chip and then moved away, the temperature of the suction nozzle is relatively low, the cooling effect of the suction nozzle on the laser chip is completely eliminated, and the solder at the bottom of the laser chip is smoothly melted, so that the eutectic welding is smoothly completed. At the same time, since the suction nozzle is moved away from the laser chip, the pressure acting on the upper surface of the laser chip is removed, when the eutectic solder is melted, the overflowed eutectic solder will reflow to the bottom of the laser chip, so that enough solder is ensured to complete the welding at the bottom of the laser.

[0027] The present application will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a COC schematic diagram of traditional laser eutectic formation;

[0029] Figure 2 is a traditional laser eutectic temperature curve diagram;

[0030] Figure 3 is a laser eutectic temperature curve diagram of the present application;

[0031] Figure 4 is a comparison diagram of laser chip thrust test after laser eutectic of the present application and traditional laser eutectic; wherein, (a) is a laser chip thrust test diagram of the present application, and (b) is a laser chip thrust test diagram of traditional laser eutectic. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0033] In the description of the present application, it should be understood that the terms "center", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings based on the orientation or positional relationship shown in the drawings, and are only intended to facilitate the description of the present application and simplify the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0034] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or abutting connection or integrally connected; for those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances; in the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0035] The embodiment provides a laser eutectic method of an optical module, comprising the following processes:

[0036] First, the laser chip is grabbed by the suction nozzle to the substrate with pre-installed eutectic solder, the suction nozzle maintains contact with the laser chip to the eutectic solder to warm up to a temperature T for 1-2 seconds, wherein T is not less than the melting point temperature of the eutectic solder. After the eutectic solder is warmed up to the temperature T, the eutectic solder has begun to melt and has a certain viscosity, at this time the suction nozzle is maintained to press the laser chip for 1-2 seconds, and the position of the laser chip is preliminarily fixed.

[0037] Then, the pressure of the nozzle on the laser chip is removed, and the eutectic solder is continuously heated at the temperature T until the eutectic solder is completely melted into a liquid state and maintained for 2-10 seconds. In this process, the nozzle is away from the upper surface of the laser chip, and the vacuum of the nozzle is closed, so that the cooling effect of the nozzle with lower temperature on the laser chip is completely eliminated, which can ensure the eutectic solder at the bottom of the laser chip to be smoothly melted, so that the eutectic soldering is smoothly completed. Moreover, since the nozzle is away from the upper surface of the laser chip, the pressure acting on the upper surface of the laser chip is removed, and when the eutectic solder is melted, the overflowed eutectic solder can be reflowed to the bottom of the laser chip, so that enough eutectic solder is ensured to complete the welding at the bottom of the laser chip.

[0038] The specific process and effect of the laser eutectic method of the optical module are described below through specific examples.

[0039] As shown in Figure 3 , the laser eutectic soldering process in the embodiment is as follows:

[0040] (1) The heating table is heated to an initial temperature, which can be any temperature below the melting point temperature of the eutectic solder from room temperature, and is set according to actual needs. In the embodiment, the eutectic solder is gold-tin solder, and the melting temperature thereof is 280°C. In the embodiment, the initial temperature of the preheating of the heating table is 240°C. By preheating the heating table, on the one hand, the time for subsequent heating to above the melting point temperature of the eutectic solder is saved, and the work efficiency is improved. On the other hand, the preheated heating table can preliminarily heat the eutectic solder, which is beneficial to the subsequent fixation of the components on the substrate.

[0041] (2) The nozzle of the automatic die bonder eutectic machine is used to grab the aluminum nitride substrate to the preheated heating table.

[0042] (3) The nozzle is used to grab the laser chip to the heating table, and the position of the laser chip is fixed by keeping the nozzle in contact with the upper surface of the laser chip. The contact pressure of the nozzle is 10 g.

[0043] (4) The heating table is heated from 240°C to 320°C, and this process takes 3 seconds. From the 3rd second to the 4th second, the nozzle maintains contact with the upper surface of the laser chip.

[0044] (5) From the 4th second, the vacuum of the nozzle is closed, and the nozzle is raised to leave the upper surface of the laser chip. In this process, the heating table continues to maintain 320°C for 9 seconds.

[0045] (6) The heating table is cooled to the initial temperature of 240°C, and a COC eutectic finished product is completed.

[0046] The laser eutectic soldering process in the embodiment is used (as shown in Figure 3The laser eutectic method of the present application is used to make the COC eutectic product shown in the figure, and the traditional laser eutectic soldering process (such as Figure 2 The COC eutectic product made by the laser eutectic method of the present application is subjected to chip thrust test, and the thrust test result is shown in the figure Figure 4 The specific operation process of the thrust test is prior art, and thus will not be described here. It can be seen from the figure that Figure 4 It can be seen that the COC eutectic product made by the laser eutectic method of the present application has a large amount of laser chip material remaining at the welding position after the thrust test, indicating that the welding quality of the COC eutectic product is good.

[0047] The above examples are only illustrative of the present application and do not constitute a limitation on the protection scope of the present application. Any design identical or similar to the present application falls within the protection scope of the present application.

Claims

1. A laser eutectic method for an optical module, characterized in that, Specifically, the steps include the following: 1) Preheating heating table; 2) The nozzle of the automatic chip eutectic bonding machine picks up the substrate pre-filled with eutectic solder and places it onto the preheated heating stage; 3) The nozzle of the automatic die bonding machine picks up the laser chip and places it at the corresponding position on the substrate, and keeps the nozzle in contact with the upper surface of the laser chip to fix the position of the laser chip. 4) Heat the heating stage to temperature T and maintain it for 1 to 2 seconds, keeping the nozzle in contact with the laser chip. T should not be less than the melting point temperature of the eutectic solder. 5) Continue to maintain the temperature T on the heating stage, close the vacuum of the suction nozzle, and at the same time remove the suction nozzle from the upper surface of the laser chip until the eutectic solder is completely melted into a liquid state and maintained for 2 to 10 seconds; 6) Cool down the heating platform and fix the laser chip.

2. The laser eutectic method for optical modules as described in claim 1, characterized in that: The eutectic solder is gold-tin solder.

3. The laser eutectic method for optical modules as described in claim 2, characterized in that: The preheating temperature of the heating platform is from room temperature to 260°C.

4. The laser eutectic method for optical modules as described in claim 3, characterized in that: The preheating temperature of the heating platform is 240°C.

5. The laser eutectic method for an optical module as described in claim 1, characterized in that: In step 3), the contact pressure between the nozzle and the laser chip is 10g.

6. The laser eutectic method for an optical module as described in claim 2, characterized in that: In steps 4) and 5), the heating temperature T of the heating platform is 320℃.

7. The laser eutectic method for an optical module as described in claim 2, characterized in that: In step 6), the temperature of the heating platform is reduced to 240°C.

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