A semiconductor laser bar stacking array and packaging method thereof

Abstract

The present invention discloses a semiconductor laser bar stack array and a packaging method thereof. The bar stack array includes multiple stacking groups, an electrically insulating heat sink and a heat sink, each stacking group includes a bar and two conductive heat dissipation blocks, the bar is welded between the two conductive heat dissipation blocks, and the stacking groups are welded to each other. A plurality of gold soldering points are arranged on the bottom surface of each conductive heat dissipation block, and both sides of the bottom surface have chamfers. The middle two chamfers of each stacking group are non-gold-plated chamfers, and the two chamfers on both sides are gold-plated chamfers. The top surface of the electrically insulating heat sink is provided with a plurality of electrically insulating grooves. A semiconductor laser bar stack array and a packaging method thereof in the present invention solves the problem of solder extrusion by distinguishing between gold-plated chamfers and non-gold-plated chamfers on both sides of the conductive heat dissipation block, and also solves the problem of uncontrollable solder extrusion caused by the height difference of the conductive heat dissipation blocks on both sides of the bar by making soldering points on the conductive heat dissipation block and the heat sink.

Description

Technical Field

[0001] The present invention relates to the field of lasers, and in particular to a semiconductor laser bar stack array and a packaging method thereof. Background Art

[0002] The current high-temperature hard solder semiconductor laser bar stacking packaging structure generally alternately stacks n bars and n+1 conductive heat dissipation spacers (such as tungsten copper, copper, diamond copper, etc.), and reflow solders them with a whole piece of electrically insulating heat sink (such as gold-plated or copper-clad aluminum nitride / aluminum oxide / beryllium oxide ceramic sheet, etc.) and a heat sink (usually a copper block) to form a laser bar stacking unit.

[0003] The preparation process of the packaging structure is generally to first weld each bar and each conductive heat dissipation spacer into a module using high-temperature hard solder (such as gold-tin, gold-germanium, etc.), and then weld the module and the electrically insulating heat sink for a second time using relatively low-temperature soft solder (such as indium / indium silver / indium tin, etc.). At the same time, the electrically insulating heat sink and the heat sink are welded using relatively low-temperature soft solder.

[0004] During the welding process of each bar and each conductive heat sink in the preparation process of the above-mentioned packaging structure, it is generally ensured that the light-emitting surface of the bar (the upper surface in the figure) is aligned. Since the height of the conductive heat sink spacers on both sides generally deviates, it will further cause errors in the height of the lower surface, so that the welding surface in the final welding process is not a plane, which not only poses the risk of empty welding, but also causes the light emission directionality of the bar to be off-angled.

[0005] In addition, in the process of preparing the above-mentioned packaging structure, the welding effect that needs to be achieved is that there is no empty solder at the welding interface between the bar and the conductive heat dissipation spacer, there is less solder overflow on the front cavity surface of the bar and the conductive heat dissipation spacer, and there is no solder short circuit as a whole. However, in the actual product preparation process, since the height of the conductive heat dissipation spacers on both sides of the bar often deviates, and the indium solder is easy to migrate during the high-temperature reflow process, if the pressure and reflow temperature are fixed, the solder is too thin, it is easy to cause empty solder at the welding interface, and conversely, the solder is too thick, it is easy to cause solder extrusion and then cause solder short circuit; at the same time, if the reflow temperature and solder thickness are fixed, the pressure is too low, it is easy to cause empty solder at the welding interface or the light directivity of the bar is deviated due to the height error of the lower surface of the conductive heat dissipation spacers on both sides of the bar, and conversely, the pressure is too high, it is easy to cause solder extrusion and then cause solder short circuit. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a semiconductor laser bar stack array and a packaging method thereof, which solves the solder extrusion problem by distinguishing between gold-plated chamfers and non-gold-plated chamfers on both sides of the conductive heat dissipation block. At the same time, by making solder points on the conductive heat dissipation block and the heat sink, the problem of uncontrollable solder extrusion caused by the height difference of the conductive heat dissipation spacers on both sides of the bar is solved.

[0007] According to one aspect of the present invention, there is provided a semiconductor laser bar stack array, comprising a plurality of stacking groups, an electrically insulating heat sink and a heat sink, each of the stacking groups comprising a bar and two conductive heat sink spacers, the bar being welded between the two conductive heat sink spacers, the stacking groups being welded to each other, and the bottom surface of each conductive heat sink spacer being welded to the top surface of the electrically insulating heat sink, and the bottom surface of the electrically insulating heat sink being welded to the top surface of the heat sink;

[0008] A plurality of gold solder joints are arranged on the bottom surface of each of the conductive heat dissipation spacers, and both sides of the bottom surface have chamfers, the two middle chamfers of each stacking group are non-gold-plated chamfers, and the two chamfers on both sides are gold-plated chamfers;

[0009] The top surface of the electrically insulating heat sink is provided with a plurality of electrically insulating grooves, each of the electrically insulating grooves is respectively located directly below the two non-gold-plated chamfers of each stacking group, and each side surface of the electrically insulating groove is not gold-plated.

[0010] In some embodiments, the bar is welded between two conductive heat dissipation spacers by hard solder, the conductive heat dissipation spacers of two adjacent stacked groups are welded by soft solder, the bottom surface of each conductive heat dissipation spacer is welded to the top surface of the electrical insulation heat sink by soft solder, and the bottom surface of the electrical insulation heat sink is welded to the top surface of the heat sink by soft solder. The benefit lies in that the solder selected for each welding position is described.

[0011] In some embodiments, the hard solder is made of gold-tin or gold-germanium materials, and the soft solder is made of indium, indium-silver, or indium-tin materials. It is beneficial to describe suitable selection materials for the hard solder to merge into the soft solder.

[0012] In some embodiments, the gold solder joint is made of soft gold and has a height of 20 μm to 50 μm. The benefit is that the material and size of the gold solder joint are described, and the gold solder joint will be deformed to a certain extent under the action of pressure.

[0013] In some embodiments, two separate conductive heat dissipation spacers are respectively provided on both sides of all the stacking groups. The benefit is that the separate conductive heat dissipation spacers provided on both sides can be used for fixing with a clamp during processing, and the relationship between the two separate conductive heat dissipation spacers and the adjacent stacking groups also conforms to the above arrangement.

[0014] In some embodiments, the height of the conductive heat dissipation spacer minus the length of the chamfered edge is not less than the length of the bar. The benefit of this is that it describes the specific size relationship between the conductive heat dissipation spacer and the bar.

[0015] In some embodiments, the top and bottom surfaces of the electrically insulating heat sink are plated with gold. The advantage is that the gold plating on the top and bottom surfaces of the electrically insulating heat sink can facilitate solder climbing.

[0016] In some embodiments, a plurality of solder joints are provided on the top surface of the heat sink, which is beneficial in that the provision of solder joints can apply greater pressure to fix the heat sink and ensure that the solder thickness between the heat sink and the electrically insulating heat sink is not too thin, so that the solder extrusion amount is controllable.

[0017] According to another aspect of the present invention, a packaging method for the semiconductor laser bar stack array is provided, comprising the following steps:

[0018] S1: assembling the stacked array of bars;

[0019] S2: placing the stack of bars in a fixture and applying pressure from the side and top to fix it;

[0020] S3: placing the fixture and the stacked array of bars in a vacuum reflow furnace for heating to melt each solder sheet for reflow soldering, wherein the solder extruded from around the conductive heat dissipation spacer climbs along each gold-plated chamfer and fills into a triangular area formed by the two gold-plated chamfers between each two adjacent stacking groups and the top surface of the electrically insulating heat sink, and the extruded solder does not climb along each non-gold-plated chamfer and the electrically insulating groove.

[0021] In some embodiments, in step S2, when pressure is applied, the gold solder joints on the bottom surfaces of the conductive heat dissipation spacers of different heights are compressed and deformed in different amounts, and the upper surfaces of the conductive heat dissipation spacers are flush. This is beneficial in that it describes the effect of the gold solder joints when under pressure, and can ensure the consistency of the light output direction of the bar strips. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic structural diagram of a semiconductor laser bar stack array and a packaging method thereof according to an embodiment of the present invention;

[0023] Figure 2 for Figure 1 A schematic diagram of the structure of the conductive heat dissipation spacer shown;

[0024] Figure 3 for Figure 1 A schematic diagram of the structure of the stacking group shown;

[0025] Figure 4 for Figure 1 A schematic diagram of the structure of the electrical insulating heat sink shown;

[0026] Figure 5 for Figure 1A schematic diagram of a part of the structure of two stacking groups of the bar stack array and the electrical insulation heat sink before being fixed and reflow soldering;

[0027] Figure 6 for Figure 1 The schematic diagram of the partial structure of two stacking groups of the bar stack array and the electrical insulation heat sink after being fixed and reflow soldered.

[0028] In the figure: stacking group 1, electrically insulating heat sink 2, heat sink 3, bar 4, conductive heat dissipation spacer 5, gold solder joint 6, chamfer 7, non-gold-plated chamfer 8, gold-plated chamfer 9, electrically insulating groove 10, triangular area 11. DETAILED DESCRIPTION

[0029] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0030] like Figure 1 As shown, the bar stack array includes a plurality of bar bars 4, a plurality of conductive heat dissipation spacers 5, an electrically insulating heat sink 2 and a heat sink 3. The bar bars 4 and the conductive heat dissipation spacers 5 are divided into a plurality of stacking groups 1, each stacking group 1 includes a bar bar 4 and two conductive heat dissipation spacers 5, and the bar bar 4 is stacked between two conductive heat dissipation spacers 5. The conductive heat dissipation spacers 5 of each stacking group 1 are placed on the electrically insulating heat sink 2, and the electrically insulating heat sink 2 is placed on the heat sink 3.

[0031] In addition, two separate conductive heat dissipation spacers 5 are respectively provided on both sides of all stacking groups 1 for fixing with a clamp during processing.

[0032] The two sides of the bar 4 of each stacking group 1 are welded to the two conductive heat dissipation spacers 5 by hard solder, the two conductive heat dissipation spacers 5 of adjacent stacking groups 1 are welded by soft solder, the bottom surface of all the conductive heat dissipation spacers 5 of each stacking group 1 are welded to the top surface of the electrically insulating heat sink 2 by soft solder (the soft solder there can be slightly thicker), and the bottom surface of the electrically insulating heat sink 2 and the top surface of the heat sink 3 are welded by soft solder.

[0033] Preferably, the hard solder is a high-temperature hard solder such as gold-tin or gold-germanium, and the soft solder is indium, indium-silver, indium-tin, etc., which has a reflow temperature lower than that of the high-temperature hard solder.

[0034] like Figure 2-3 As shown, a plurality of gold solder joints 6 are arranged on the bottom surface of each conductive heat dissipation spacer 5, and both sides of the bottom surface have chamfers 7. Among the four chamfers 7 of the two conductive heat dissipation spacers 5 in each stacking group 1, the two middle chamfers 7 are non-gold-plated chamfers 8, and the two chamfers 7 on both sides are gold-plated chamfers 9.

[0035] In addition, the relationship between two separate conductive heat dissipation spacers 5 and adjacent stacking groups 1 also conforms to the above arrangement.

[0036] Preferably, the gold solder joint 6 is made of soft gold, has a height between 20 μm and 50 μm, and will produce a certain deformation under the action of pressure.

[0037] The height of the conductive heat dissipation spacer 5 is slightly greater than the length of the bar 4, and even if the height of the conductive heat dissipation spacer 5 minus the side length of the chamfer 7 is not less than the length of the bar 4. For example, if the height of the conductive heat dissipation spacer 5 is 2.65 mm, and when it is matched with the bar 4 with a cavity length of 2.5 mm, the chamfer 7 is suitably set within the range of 0.1 mm to 0.15 mm, and in order to improve the heat dissipation effect, the side length of the chamfer 7 is as wide as possible within the adjustable range.

[0038] like Figure 4 As shown, the top surface of the electrically insulating heat sink 2 is provided with a plurality of electrically insulating grooves 10, and each electrically insulating groove 10 is respectively located directly below the two non-gold-plated chamfers 8 of each group of conductive heat sinks 5. Among them, the top and bottom surfaces of the electrically insulating heat sink 2 are both gold-plated, but the inner side surface and bottom side surface of each electrically insulating groove 10 are not gold-plated.

[0039] In addition, a plurality of solder joints (not shown in the figure) are also arranged on the top surface of the heat sink 3 . The design and material of each solder joint can refer to the above-mentioned gold solder joint 6 .

[0040] The present invention also provides a packaging structure preparation method using the above-mentioned high-reliability semiconductor laser array packaging structure preparation fixture, which includes the following main steps S1 to S3.

[0041] S1: Assemble the bar array.

[0042] As described above, the bar stack array is assembled using multiple bar strips 4, multiple conductive heat dissipation spacers 5, an electrically insulating heat sink 2 and a heat sink 3, wherein each hard solder and soft solder can be selectively set at the corresponding position using solder sheets.

[0043] like Figure 5 As shown, after assembly, the heights of the conductive heat dissipation spacers 5 are often inconsistent, and the bottom surface appears uneven.

[0044] S2: Fix the stacked bars with a clamp.

[0045] In this step, the stack of bar arrays is placed in a corresponding fixing fixture, and the fixture is used to fix the stack of bar arrays, including applying corresponding pressure from the side and top to fix the stack of bar arrays.

[0046] S3: The fixture and the stack of bars thereon are placed in a vacuum reflow oven for heating to melt the solder and perform reflow soldering.

[0047] like Figure 6 As shown, after fixation and reflow soldering, each solder begins to melt, and with the pressure applied from above by the fixture, the solder around each conductive heat dissipation spacer 5 will be squeezed out. Since the heights of different conductive heat dissipation spacers 5 are inconsistent, the amount of solder extrusion will be different, and the extruded solder will tend to climb along the chamfers 7 of the conductive heat dissipation spacer 5.

[0048] Among them, since the two chamfers 7 on both sides of the stacking group 1 are gold-plated chamfers 9, and the top surface of the electrically insulating heat sink 2 is also gold-plated, they can be wetted with the solder, making it convenient for the solder to climb. Therefore, the squeezed excess solder will climb and spread along the gold-plated chamfers 9 and fill in the triangular area 11 formed by the two gold-plated chamfers 9 and the top surface of the electrically insulating heat sink 2 between each adjacent stacking group 1.

[0049] Since the two chamfers 7 in the middle of the stacking group 1 are non-gold-plated chamfers 8, and the electrical insulating grooves 10 below the two non-gold-plated chamfers 8 are not gold-plated, they are not wetted by the solder, so that the solder cannot climb up. Therefore, it is possible to prevent the extruded excess solder from climbing to that place, avoiding the formation of solder balls and further causing the solder to be squeezed out and short-circuited.

[0050] In addition, since there are gold solder joints 6 on the bottom surface of the conductive heat dissipation spacer 5, which will be deformed under the action of pressure, in terms of pressure control, a larger pressure can be applied to the conductive heat dissipation spacer 5 to fix it. Even if the heights of the conductive heat dissipation spacers 5 at different positions are different, the compression deformation amounts of the gold solder joints 6 will also be different. Therefore, the upper surfaces of the conductive heat dissipation spacers 5 can still be kept flush, ensuring the consistency of the light emitting direction of the bar 4. During the welding process, the presence of the gold solder joints 6 will ensure that the solder thickness between the conductive heat dissipation spacer 5 and the electrically insulating heat sink 2 will not be too thin, so that the solder extrusion amount can be controlled.

[0051] Similarly, the solder joints on the heat sink 3 can also be fixed by applying greater pressure in terms of pressure control, and during the welding process, it is ensured that the solder thickness between the heat sink 3 and the electrically insulating heat sink 2 is not too thin, so that the solder extrusion amount can be controlled to avoid excessive solder extrusion and cause a short circuit.

[0052] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the creative concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A semiconductor laser bar stack array, characterized in that: It comprises a plurality of stacking groups, an electrically insulating heat sink and a heat sink, each of the stacking groups comprises a bar and two conductive heat sinking blocks, the bar is welded between the two conductive heat sinking blocks, the stacking groups are welded to each other, and the bottom surface of each conductive heat sinking block is welded to the top surface of the electrically insulating heat sink, and the bottom surface of the electrically insulating heat sink is welded to the top surface of the heat sink; A plurality of gold solder joints are arranged on the bottom surface of each of the conductive heat dissipation spacers, and both sides of the bottom surface have chamfers, the two middle chamfers of each stacking group are non-gold-plated chamfers, and the two chamfers on both sides are gold-plated chamfers; The top surface of the electrically insulating heat sink is provided with a plurality of electrically insulating grooves, each of the electrically insulating grooves is respectively located directly below the two non-gold-plated chamfers of each stacking group, and each side surface of the electrically insulating groove is not gold-plated; The gold-plated chamfer is wetted by the solder, while the non-gold-plated chamfer and the side surfaces of the non-gold-plated electrical insulating groove are not wetted by the solder.

2. The semiconductor laser bar stack array according to claim 1, characterized in that: The bar is welded between two conductive heat dissipation spacers by hard solder, the conductive heat dissipation spacers of two adjacent stacking groups are welded by soft solder, the bottom surface of each conductive heat dissipation spacer is welded to the top surface of the electrically insulating heat sink by soft solder, and the bottom surface of the electrically insulating heat sink is welded to the top surface of the heat sink by soft solder.

3. The semiconductor laser bar stack array according to claim 2, characterized in that: The hard solder is made of gold-tin or gold-germanium materials, and the soft solder is made of indium, indium-silver or indium-tin materials.

4. The semiconductor laser bar stack array according to claim 1, characterized in that: The gold solder joint is made of soft gold and has a height of 20 μm to 50 μm.

5. The semiconductor laser bar stack array according to claim 1, characterized in that: Two separate conductive heat dissipation spacers are respectively arranged on both sides of all the stacking groups.

6. The semiconductor laser bar stack array according to claim 1, characterized in that: The height of the conductive heat dissipation spacer minus the length of the chamfered edge is not less than the length of the bar.

7. The semiconductor laser bar stack array according to claim 1, characterized in that: The top and bottom surfaces of the electrically insulating heat sink are plated with gold.

8. The semiconductor laser bar stack array according to claim 1, characterized in that: A plurality of solder joints are arranged on the top surface of the heat sink.

9. A method for packaging a semiconductor laser bar stack array according to any one of claims 1 to 8, characterized in that: The following steps are included S1: assembling the stacked array of bars; S2: placing the stack of bars in a fixture and applying pressure from the side and top to fix it; S3: placing the fixture and the stacked array of bars in a vacuum reflow furnace for heating to melt each solder sheet for reflow soldering, wherein the solder extruded from around the conductive heat dissipation spacer climbs along each gold-plated chamfer and fills into a triangular area formed by the two gold-plated chamfers between each two adjacent stacking groups and the top surface of the electrically insulating heat sink, and the extruded solder does not climb along each non-gold-plated chamfer and the electrically insulating groove.

10. The method for packaging a semiconductor laser bar stack array according to claim 9, characterized in that: In step S2, when pressure is applied, the gold solder joints on the bottom surfaces of the conductive heat dissipation spacers of different heights are subjected to different amounts of compression deformation, and the upper surfaces of the conductive heat dissipation spacers are flush.

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