CN103457151A - High-temperature hard solder quasi-continuous semiconductor laser bar stack encapsulating method - Google Patents

Abstract

The invention discloses a high-temperature hard-solder quasi-continuous semiconductor laser bar stacking packaging method, using special fixtures and high-temperature hard solder to insulate n bars, n+1 conductive and heat-dissipating spacers and n+1 electrical insulation The heat sinks are alternately stacked and reflow-welded once to form a laser bar stacked array unit, and then the laser bar stacked array unit and the heat sink are reflow-welded again to form a laser bar stacked array unit with a relatively low temperature soft solder. The method can significantly reduce the welding stress when the high-temperature hard solder quasi-continuous semiconductor laser is packaged in bar stacks, and improve the lifespan, output rate and photoelectric performance of the device.

Description

A high-temperature hard-solder quasi-continuous semiconductor laser bar-stack packaging method

technical field

The invention relates to the field of laser technology, in particular to a bar-stack packaging method for high-temperature hard solder quasi-continuous semiconductor lasers. the

Background technique

Due to its small size, light weight, and high electro-optical conversion efficiency, semiconductor lasers are widely used in industries, medical care, communications, military defense and other fields. The application market has higher and higher requirements for high power, especially the peak power of quasi-continuous output, and the high-power vertical stack and area array assembled by multiple bars have developed rapidly. the

At present, the high-power vertical stacks assembled by multiple bars are mainly stacked with single-bar semiconductor lasers packaged in micro-channel heat sinks. The micro-channel heat sink uses deionized water to remove the heat generated by the laser from the bar in time, and the heat dissipation efficiency is high. However, the microchannel heat sink using this method of heat dissipation requires a special design, and the design and production costs are very high; secondly, the volume of the semiconductor laser array using this packaging method is much larger than that of the conduction cooling semiconductor laser array, and it needs to be equipped with water cooling. The machine can work normally; again, this packaging method needs to minimize the corrosion and wear of the heat sink material while effectively dissipating heat from the laser. Generally, it is required to use deionized water. Once the inside of the microchannel is corroded or there are metal debris Peeling, or particles in the cooling water, etc., the cooling capacity of the microchannel will decrease, resulting in a sharp decline in device performance, red shift in the spectrum, etc., and the requirements for working conditions are very harsh. the

In addition, the solder used for single-bar semiconductor lasers packaged with microchannel heat sinks is mainly high-purity indium. High-purity indium is a kind of soft solder with good ductility, which can well compensate the thermal expansion coefficient mismatch between heat sink material and bar material during device packaging (especially in the cooling stage) and device working state, and The wettability of the welding surface with the p-side gold-plated layer of the semiconductor laser bar is also very good. The disadvantage of indium solder is that when mechanical and thermal cycles occur at the indium interface, the plastic deformation rate is high and creep is easy to occur. Indium solder is easily oxidized during sintering and welding, and an oxide film with high melting point, poor wettability, and solder resistance is formed on its surface, which reduces the soldering performance of the device. And it is easy to produce indium whiskers, which can easily lead to the short circuit of the P and N junctions of the bar and the pollution of the cavity surface of the bar. When the device is working, indium solder is prone to electromigration and electrothermal migration under high current, which reduces the stability of the device and is prone to sudden degradation. The life of the device packaged with indium solder is much shorter than that of the device packaged with gold-tin solder. the

Therefore, the application of high-temperature hard-solder quasi-continuous semiconductor laser bar-stack packaging technology was born. The methods disclosed in U.S. Patent Nos. 5,040,187 and 5,284,790 are to cut out a plurality of spaced, parallel and separated rectangular grooves in the electrically insulating and heat-conducting substrate. An electrical connection of the metallization takes place from the walls of these parallel separated grooves to the walls of the adjacent grooves. The width of the groove is chosen to be slightly smaller than the thickness of a single laser bar. The thermally conductive substrate can be bent in another direction under the action of external force, so that the distance between the grooves is larger, and the semiconductor laser bar can be inserted into it. When the external force is removed and the substrate returns to its normal position, the laser bar is firmly compressed and fixed in the groove of the substrate, realizing multiple electrical connections between the laser bar in the groove and the surface of the metallized substrate. conductive connection. In this method, in order to avoid cracking of the bars due to stress during packaging, soft solder, such as indium, is selected. In addition, this method is not conducive to the alignment of the front end of the laser bar, and the bar is easy to translate or rotate in the groove during the packaging process. the

US Patent No. 5,128,951 shows an improvement on the basis of the above method, which is a simpler method for manufacturing a laser bar array. The heat sink substrate is composed of two layers, the upper part is a conductive and heat-conducting layer, and the lower part is an electrically insulating and heat-conducting layer. The two layers can be connected together by welding or other means. After cutting out the groove array on the upper layer, laser bars can be placed, and then welded together by reflow. However, there is still no way to provide a better front-end alignment of the laser bars. the

US Patent No. 5,305,344 discloses inserting a semiconductor laser bar heat sink, rather than the laser bar itself, into a groove on the top surface of a substrate. The heat sink consists of a laser bar, alumina spacers, and tungsten-copper alloy heat sinks. The bar at the front end of the tungsten-copper heat sink is connected with the upper surface of the metallized alumina pad with gold foil. The spacer is located in the middle of the heat sink. Paste the soft solder on the inner walls of the grooves distributed in parallel and equally spaced on the substrate. The rear end of the tungsten-copper alloy heat sink is inserted into the groove. The electrical connections between the laser bars in the stack are made by adding copper spacers between the heat sink and the top of the alumina spacer. Unfortunately, failure modes such as laser bar performance degradation, solder creeping onto the bar surface, etc. have a high chance of occurring with failure modes such as joining the package. the

U.S. Patent Nos. 6,636,538 and 7,060,515, and 5,898,211 disclose different stack assembly methods to solve the above problems, that is, to provide a single laser bar module (including heat sink spacer, laser bar and electrical insulation substrate) combined into a stack . Each individual laser module can be tested to ensure that it matches the required operating parameters of the stack. The other exposed surface of the laser bar (i.e. the N side) includes a solder layer so that two or more modules can be reflowed at this special solder melting temperature and combined into a multi-bar stack. U.S. Patent No. 6,424,667 discloses a similar method, that is, two heat sink pads with matching thermal expansion coefficients are used to sandwich the laser bars and weld them together, and then the heat sink pads are perpendicular to the other side of the bar welding surface. An electrically insulating and thermally conductive material substrate is pasted on the surface to form a sub-module of the laser bar. Later, multiple sub-modules are pasted together and welded to a large heat sink to form a stack of laser bars. This invention greatly improves the resistance of laser bar stacks to thermal cycle fatigue. However, these methods above all require multiple reflow assembly processes with many different solders (different melting points), which makes the process cumbersome and inefficient. In addition, the period of the laser bars in the stack has certain limitations, which cannot be small enough to meet many practical requirements and applications. the

U.S. Patent Nos. 6,295,307 and 6,352,873 disclose a method of assembling semiconductor laser bar stacks. That is, put the first conductive pad alloy, paste the first solder sheet, place the bar on the first solder sheet, then paste the second solder sheet, place the second conductive pad alloy, and use The jig compresses and fixes the block, bar, and block together, heats them to a temperature higher than the melting point of the solder for reflow, and cools to harden. This sandwich-type production process can be extended to the production process of multiple laser bar stacks. The conductive heat sink block-bar composite assembly is bonded to the non-conductive heat sink substrate in this way: the upper surface of the non-conductive heat sink substrate is metallized or coated with conductive material, and a plurality of grooves are cut out to pass through the substrate to conduct electricity. layer. The groove spacing corresponds to the arrangement period of the bars, the conductive heat dissipation pads are welded to the conductive layer of the non-conductive heat sink substrate, and the laser bars are just located above the grooves. The lower surface of the substrate is then soldered to a thermally conductive substrate containing a coolant. The heat conduction matrix, the non-conductive heat sink substrate, and the conduction heat dissipation pad-bar composite assembly are all welded together to have a good heat conduction effect. U.S. Patent No. 7,864,825 provides a laser bar stack packaging method, which changes the sequence of reflow soldering of different components: the metallized non-conductive heat sink substrate is first welded to a larger heat-conducting substrate, and the cut multi-element parallel The groove passes through the non-conductive heat sink substrate to form a parallel street-type multi-element heat sink. The multi-element laser bars and conductive heat dissipation pads composed of laser bars are welded to the surface electrically insulated through the grooves, and the bars are just right The non-conductive heat sink substrate located above the groove is soldered to the conductive heat dissipation pad. In this assembled condition, the individual heat sink substrates are free to move as the heat sink expands. However, when reflowing with high-temperature hard solder, due to the stress caused by the inconsistent thermal expansion coefficients of different materials, the performance of the laser bars in the stack may still be degraded, and even the laser bars may be split, especially the bars arranged in the stack. In the case of large cycles. the

The oxygen-free copper heat sink is used for conduction cooling and heat dissipation, and no cooling medium such as deionized water is required. The welding between the laser bar and the conductive heat dissipation spacer is connected by high-temperature hard solder to form a stable alloy phase with high welding strength and can work under extremely harsh conditions such as -40°C to 85°C. However, the high-temperature hard solder is easy to cause a large strain on the bar, and the large welding stress makes the bar easy to crack, resulting in failure of the laser. Therefore, there is an urgent need for a packaging method for stacking arrays of quasi-continuous semiconductor lasers that adopts high-temperature hard solder welding and low stress. the

Contents of the invention

The object of the present invention is to overcome the above problems in the prior art, provide a high-temperature hard solder quasi-continuous semiconductor laser bar-stack packaging method, and significantly reduce the welding stress during the high-temperature hard-solder quasi-continuous semiconductor laser bar stack packaging. the

In order to achieve the above-mentioned technical purpose and achieve the above-mentioned technical effect, the present invention is realized through the following technical solutions:

A high-temperature hard solder quasi-continuous semiconductor laser bar stack packaging method, comprising the following steps:

Step 1) Place super-flat alumina on the bottom surface of the first fixture, first place a super-flat alumina on the bottom surface of the first fixture, and then place another super-flat alumina and several conductive and heat-dissipating spacers from one end , the conductive and heat-dissipating spacers are equally spaced apart by laser bars and high-temperature hard solder, and spring pins or screws are placed at the other end of the first tooling fixture to connect the laser bars, high-temperature hard solder, and conductive The heat dissipation spacer is fixed; or the two welding surfaces of the conductive heat dissipation spacer are plated with high-temperature hard solder to replace the preformed separately placed high-temperature hard solder sheet;

Step 2) Making an electrical insulating heat sink, metallizing the unprocessed electrical insulating heat sink, coating the outermost layer of the welding surface with a layer of gold, and then manufacturing an electrical insulating heat sink matching the size of the conductive heat dissipation spacer, Insulation is maintained between the welding surfaces of the electrically insulating heat sink;

Step 3) Use precision machining or micro-nano processing technology to make the second fixture, make n grooves on the second fixture, the width of the groove is slightly smaller than the width of the bar, and then insert the insulating object into the groove;

Step 4) placing the electrically insulating heat sink between each two insulating objects, and placing the high-temperature hard solder on the electrically insulating heat sink;

Step 5) Assemble the two parts of the special fixture into a whole, buckle the unit module in step 1 upside down on the unit module in step 4, so that the conductive heat dissipation spacer corresponds to the electrical insulation heat sink, and the inlaid insulation The object corresponds to the laser bar between two adjacent conductive and heat-dissipating spacers, and the special precision positioning and alignment system on the fixture is used to make the bar, the conductive and heat-dissipating spacer and the electrical Precise alignment is achieved between insulating heat sinks to ensure the alignment accuracy after welding, and then reflow welding is performed, and the special fixture is removed after one molding to obtain the bar stacked module unit;

Step 6) The bar stack module unit is welded with relatively low melting point soft solder and the large heat sink of the base, and then welded with electrodes, so as to obtain a high temperature hard solder quasi-continuous semiconductor laser bar stack.

Further, the high-temperature hard solder can be a preformed solder sheet or a plated or evaporated hard solder layer with a thickness of 5um-50um and its composition can be gold tin or gold germanium. the

Further, the number of the laser bars is greater than or equal to 1, and the interval period between two adjacent laser bars may be 0.4 mm to 2 mm. the

Further, the thermal expansion coefficient of the conductive heat dissipation spacer must match the thermal expansion coefficient of the laser bar. the

Further, the size of the laser bar is smaller than the size of the conductive heat dissipation spacer. the

Further, after metallization, the two welding surfaces of the electrical insulating fins are cut and formed, separated from each other, and independently welded and formed with the corresponding conductive and heat dissipating spacers. the

Further, the flatness and roughness of the assembly surfaces of the first fixture, the second fixture and the groove are within 10 μm, the machining accuracy of the groove is within 5 μm, and the roughness and smoothness of the super-flat alumina The degree is within 5 μm. the

The beneficial effects of the present invention are:

The present invention can guarantee the realization of the front-end alignment of each semiconductor bar of the semiconductor laser bar stack in the mode of conduction cooling and heat dissipation, low stress, high power, high brightness, narrow spectrum, no indiumization at the welding part of the bar, and small cycle, etc. Improve device lifetime, yield, and optoelectronic performance.

Description of drawings

The schematic diagram of the overall structure of Fig. 1;

Figure 2 is a schematic diagram of the assembly of the laser bar, the conductive heat dissipation spacer and the solder;

Fig. 3 Assembly diagram of laser stack unit;

Fig. 4 is a laser bar stacked module unit.

Explanation of symbols in the figure: 1. High temperature hard solder, 2. Laser bar, 3. Conductive heat dissipation spacer, 4. Electrically insulating heat sink, 5. Soft solder, 6. Heat sink, 7. Super flat alumina, 8. insulating object. the

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. the

  Referring to Figure 1, Figure 2, Figure 3, and Figure 4, a high-temperature hard-solder quasi-continuous semiconductor laser bar stack packaging method includes the following steps: 

Step 1) Place an ultra-flat alumina 7 on the bottom surface of the first fixture, first place an ultra-flat alumina 7 on the bottom surface of the first fixture, and then place another ultra-flat alumina 7 from one end, several conductive Heat dissipation spacers 3, the conductive heat dissipation spacers are spaced equally apart by laser bars 2 and high-temperature hard solder 1, and spring pins or screws are placed at the other end of the first tooling fixture to fasten the laser bars. 2. The high-temperature hard solder 1 and the conductive and heat-dissipating spacer 3 are fixed; or the two welding surfaces of the conductive and heat-dissipating spacer 3 are plated with high-temperature hard solder 1 to replace the preformed separately placed high-temperature hard solder sheet;

Step 2) Making the electrical insulation heat sink 4, metallizing the unprocessed electrical insulation heat sink, plating a layer of gold on the outermost layer of the welding surface, and then making an electrical insulation heat sink matching the size of the conductive heat dissipation spacer 3 Sheet 4, insulation is maintained between the welding surfaces of the electrical insulating heat sink;

Step 3) Using precision machining or micro-nano processing technology to make the second fixture, making n grooves on the second fixture, the width of the groove is slightly smaller than the width of the bar, and then inserting the insulating object 8 into the groove;

Step 4) placing the electrically insulating heat sink 4 between every two insulating objects 8, and placing the high-temperature hard solder 1 on the electrically insulating heat sink 4;

Step 5) Assemble the two parts of the special fixture into a whole, buckle the unit module in step 1 upside down on the unit module in step 4, so that the conductive heat dissipation spacer 3 corresponds to the electrical insulation heat sink 4, and inlays The insulating object 8 corresponds to the laser bar 2 between two adjacent conductive heat dissipation spacers 3, and the special precision positioning and alignment system on the tooling fixture is used to make the bar 2 and the conductive heat dissipation Precise alignment is realized between the spacer 3 and the electrical insulation heat sink 4 to ensure the alignment accuracy after welding, and then reflow welding is performed, and the special fixture is removed after one-time molding to obtain the bar stacked module unit;

Step 6) The bar stacking module unit is formed by welding the relatively low melting point soft solder 5 and the large heat sink 6 of the base, and then welding the electrodes, so as to obtain a high temperature hard solder quasi-continuous semiconductor laser bar stacking.

Further, the high temperature hard solder 1 can be a preformed solder sheet or a plated or evaporated hard solder layer with a thickness of 5um-50um and its composition can be gold tin or gold germanium. the

Further, the number of said laser bars 2 is greater than or equal to 1, and the interval period between two adjacent laser bars 2 may be 0.4 mm to 2 mm. the

Further, the thermal expansion coefficient of the conductive heat dissipation spacer 3 must match the thermal expansion coefficient of the laser bar 2 . the

Further, the size of the laser bar 2 is smaller than the size of the conductive heat dissipation spacer 3 . the

Further, after the two welding surfaces of the electrical insulating fin 4 are metallized, they are cut and formed, separated from each other, and independently welded and formed with the corresponding conductive and heat dissipating spacer 3 . the

Further, the flatness and roughness of the assembly surfaces of the first fixture, the second fixture and the groove are within 10 μm, the processing accuracy of the groove is within 5 μm, and the roughness and roughness of the ultra-flat alumina 7 are within 10 μm. The flatness is within 5μm. the

Claims (7)

1. the folded battle array of the quasi-continuous semiconductor laser bar of a high temperature braze material method for packing, is characterized in that, comprises the following steps:

Step 1) is placed super flat aluminium oxide (7) in the first frock clamp bottom surface, first place a super flat aluminium oxide (7) in the bottom surface of described the first frock clamp, then place again a super flat aluminium oxide (7), several conductive radiator spacer blocks (3) since an end, between described conductive radiator spacer block by laser cling to bar (2), high temperature braze material (1) separates equally spacedly, at the other end of described the first frock clamp, places spring catch or screw is fixed described laser bar bar (2), high temperature braze material (1), conductive radiator spacer block (3); Perhaps described conductive radiator spacer block (3) two solders side are coated with high temperature braze material (1), to replace the high temperature braze tablet of preformed independent placement;

Step 2) make electric insulation fin (4), by unprocessed electric insulation fin metallization, the outermost layer of solder side plates layer of gold, produce again the electric insulation fin (4) mated with described conductive radiator spacer block (3) size, keep insulation between the solder side of described electric insulation fin;

Step 3) utilizes precision optical machinery processing or micro-nano process technology to make the second frock clamp, produces n groove on the second frock clamp, and the width of groove is slightly less than the width of bar bar, then insulating bodies (8) is inlaid in groove;

Step 4) is placed described electric insulation fin (4) in the middle of every two described insulating bodies (8), at the upper described high temperature braze material (1) of placing of described electric insulation fin (4);

Step 5) is assembled into an integral body by two parts of special fixture, the unit module of step 1 is tipped upside down on the unit module of step 4, make described conductive radiator spacer block (3) corresponding with described electric insulation fin (4), the insulating bodies of inlaying (8) is corresponding on the bar bar of the laser between adjacent two conductive radiator spacer blocks (3) (2), utilize the special precision positioning on frock clamp, alignment system, make described bar bar (2), realize accurate contraposition between described conductive radiator spacer block (3) and described electric insulation fin (4), aligning accuracy after guaranteeing to weld, then carry out reflow soldering, remove special fixture after one-shot forming, obtain clinging to the folded array module of bar unit,

Step 6) will be clung to the folded array module of the bar unit slicken solder (5) and base greatly heat sink (6) welding fabrication relatively low by fusing point, then weld top electrode, thereby obtain the folded battle array of the quasi-continuous semiconductor laser bar of high temperature braze material.

2. the quasi-continuous semiconductor laser bar of high temperature braze material according to claim 1 is folded the battle array method for packing, it is characterized in that: described high temperature braze material (1) can be the hard solder bed of material of preformed solder sheet or process plating or evaporation, and thickness is that its composition of 5um～50um can be Jin Xi or golden germanium.

3. the quasi-continuous semiconductor laser bar of high temperature braze material according to claim 1 is folded the battle array method for packing, it is characterized in that: described laser bar bar (2) number is more than or equal to 1, and the gap periods between adjacent two-laser bar bar (2) can be 0.4mm～2mm.

4. the folded battle array of the quasi-continuous semiconductor laser bar of a high temperature braze material according to claim 1 method for packing is characterized in that: the thermal coefficient of expansion that the thermal coefficient of expansion of described conductive radiator spacer block (3) must cling to bar (2) with laser is complementary.

5. the quasi-continuous semiconductor laser bar of high temperature braze material according to claim 1 is folded the battle array method for packing, it is characterized in that: the size of described laser bar bar (2) is less than the size of described conductive radiator spacer block (3).

6. the quasi-continuous semiconductor laser bar of high temperature braze material according to claim 1 is folded the battle array method for packing, it is characterized in that: described electric insulation fin (4) two solders side are after metallization, excision forming, be separated from each other, the independent and corresponding corresponding welding fabrication of conductive radiator spacer block (3).

7. the quasi-continuous semiconductor laser bar of high temperature braze material according to claim 1 is folded the battle array method for packing, it is characterized in that: the evenness of the fitting surface of described the first frock clamp, the second frock clamp and groove, roughness are in 10 μ m, the machining accuracy of described groove is in 5 μ m, and the roughness of described super flat aluminium oxide (7) and evenness are in 5 μ m.

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