Soldering device and method with low bubble generation rate for semiconductor packaging

Abstract

The present invention discloses a soldering device and method with low bubble generation rate for semiconductor packaging. The soldering device of the present invention comprises a first heating part and a second heating part respectively located on both sides of a substrate, which can realize staged heating when melting solder paste. In the first heating stage, the heating temperature of the second heating part is lower than the melting temperature of the solder paste, and the heating temperature of the first heating part is not lower than the melting temperature of the solder paste. In the second heating stage, the heating temperatures of the first heating part and the second heating part both exceed the melting temperature of the solder paste. The first heating part is a heating plate, and the second heating part is a hot air heating part. The second heating part is located on one side of the substrate where the solder paste to be melted is arranged. The soldering device of the present invention also comprises a cooling part capable of cooling the hot air of the hot air heating part. By using the soldering device of the present invention, the solder paste can be gradually melted from the bottom to the outside, thereby discharging bubbles out of the solder joint, thereby effectively reducing bubbles in the solder paste and forming a good solder joint.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor packaging, and in particular to a soldering device and method with low bubble generation rate for semiconductor packaging. Background Art

[0002] When packaging semiconductor components, solder paste is heated until it melts, then connected to the substrate and cooled to form solder joints. Then, during the SMT surface mounting or solder paste process of semiconductor packaging, many voids will be formed in the solder joints, which will have a great impact on the performance of the solder joints.

[0003] The reason for the generation of bubbles is that solder paste is a paste formed by mixing flux and solder alloy powder. The flux is prepared by activating agent, solvent, rosin, etc. The various components of the flux have different vaporization temperature points. During the heating process, the flux will vaporize. Before the solder paste liquefies, part of the flux will overflow from the gaps of the alloy particles after vaporization. When the solder paste is heated to the melting point, the surface of the solder paste liquefies and generates surface tension. Some small and medium-sized bubbles are unable to break the surface tension due to insufficient pressure and are enclosed inside the solder joint, thus forming voids.

[0004] At present, the following three methods are usually used to reduce bubbles generated during solder paste melting: ① Vacuum degassing method: During solder paste melting, the pressure difference between internal bubbles and the outside world is expanded by vacuuming, so that bubbles break the surface tension and overflow from the solder joints to reduce the void rate; ② Vapor phase reflow soldering: The vapor phase liquid is heated to form an oxygen-free, steam reflow (welding) zone with good heat transfer performance, so that the gas in the solder joints can be fully volatilized during the reflow process; ③ No flux is added. The vacuum degassing method will cause the production cycle to be lengthened by about 3 times, and the pads with pins less than 0.4p ith are prone to short circuits. The other two methods also have the defects of low production efficiency and high production costs. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a soldering device and method with low bubble generation rate for semiconductor packaging.

[0006] The soldering device with low bubble generation rate for semiconductor packaging of the present invention is used for soldering connection between soldering elements and substrates, and includes a first heating part and a second heating part respectively located on both sides of the substrate. The device can realize staged heating when melting solder paste. In the first heating stage, the heating temperature of the second heating part is lower than the melting temperature of the solder paste, and the heating temperature of the first heating part is not lower than the melting temperature of the solder paste. In the second heating stage, the heating temperatures of the first heating part and the second heating part both exceed the melting temperature of the solder paste. The soldering device of the present invention is used to melt the solder paste by heating in two stages. In the first heating stage, the side of the solder paste close to the first heating part begins to melt while the part close to the second heating part does not melt. In the second heating stage, the temperature of the second heating part also rises to above the melting point of the solder paste, so that the solder paste gradually melts from the bottom to the outside, thereby gradually discharging the bubbles out of the solder joint. Therefore, the bubbles in the solder paste are effectively reduced and a good solder joint can be formed.

[0007] Further, at least one of the first heating part and the second heating part is heated by hot air, and the hot air can be blown toward the solder paste located on the substrate.

[0008] Furthermore, the first heating part is a heating plate, the second heating part is a hot air heating part, and the second heating part is located on the side of the substrate where the solder paste to be melted is disposed. Therefore, the solder paste can be gradually melted in a direction close to the second heating part on the side close to the first heating part.

[0009] Furthermore, the hot air heating part includes a plurality of hot air nozzles arranged toward the solder paste, a wind chamber connected to the hot air nozzles, and a high-temperature fan connected to the wind chamber, and at least one heater is arranged in the wind chamber.

[0010] Furthermore, a cooling unit is included to cool down the hot air of the hot air heating unit. Therefore, the hot air temperature can be quickly adjusted by the cooling unit, thereby achieving rapid adjustment of the air temperature to ensure that the surface of the solder paste is finally melted.

[0011] Furthermore, the cooling unit includes a cold air channel communicated with the air chamber and a cooling fan connected to the cold air channel, and a heat exchanger for cooling is arranged in the cold air channel.

[0012] Furthermore, at least one return air hole is arranged around each of the hot air nozzles, and a negative pressure pipe is also provided which is connected to the return air hole. Therefore, after the hot air nozzle blows out the air to a certain distance, it can flow back through the return air hole to form a small cycle, and no lateral airflow will be generated, so that a better welding point can be obtained.

[0013] The present invention also provides a method for reducing solder bubbles in a semiconductor packaging process, wherein a first heating unit and a second heating unit are respectively provided on both sides of a substrate, and the heating and melting process of the solder paste includes at least a first heating stage and a second heating stage, wherein the heating temperature of the first heating unit in the first heating stage is not less than the melting temperature of the solder paste, the heating temperature of the second heating unit in the first heating stage is not more than the melting temperature of the solder paste, and the heating temperatures of the first heating unit and the second heating unit in the second heating stage both exceed the melting temperature of the solder paste. By using the method of the present invention, the solder paste can be gradually melted from the bottom to the top, thereby slowly gathering bubbles upward, and rapidly discharging the bubbles in the second heating stage, thereby forming a good solder joint, and effectively reducing the generation rate of bubbles in the solder joint.

[0014] Furthermore, the first heating part is a heating plate, and the second heating part heats the solder paste by hot air.

[0015] Furthermore, the heating temperature of the second heating part does not exceed the heating temperature of the first heating part. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention;

[0017] Figure 2 for Figure 1 A local enlarged schematic diagram of the middle A;

[0018] Figure 3 This is a schematic diagram of the heating principle of the first embodiment of the present invention;

[0019] Figure 4 : is a temperature curve of the first heating unit and the second heating unit in the first heating stage and the second heating stage of the first embodiment of the present invention, T1 is the wind temperature of the second heating unit, and T3 is the heating temperature of the first heating unit;

[0020] Figure 5a A schematic diagram of bubble distribution in a solder joint of tin soldering in the prior art;

[0021] Figure 5b A schematic diagram of bubble distribution in a solder joint of tin soldering in the prior art;

[0022] Figure 6a A schematic diagram of bubble distribution in a solder joint when soldering is performed using the device of the present invention;

[0023] Figure 6b The figure is a schematic diagram of bubble distribution in a solder joint when soldering is performed using the device of the present invention.

[0024] In the figure:

[0025] 1-welding element, 2-substrate, 3-solder paste, 4-first heating part, 5-second heating part, 51-hot air nozzle, 52-wind chamber, 53-high temperature fan, 54-heater, 61-cold air channel, 62-cooling fan, 63-heat exchanger, 64-return air hole, 65-negative pressure duct. DETAILED DESCRIPTION

[0026] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0027] Embodiment 1:

[0028] See attached Figure 1 and 2 As shown, as a preferred embodiment of the soldering device with low bubble generation rate for semiconductor packaging of this embodiment, it is used to solder the welding component 1 and the substrate 2. When in use, the solder paste 3 is set on the substrate 2, and the solder paste 3 is melted by the device of the present invention, and the pins of the welding component 1 are inserted into the melted solder paste 3, and then the solder paste 3 is cooled to complete the soldering process.

[0029] The device of the present invention includes a first heating part 4 and a second heating part 5 respectively located on both sides of the substrate 2. The device of the present invention can realize staged heating when melting the solder paste 3. In the first heating stage S1, the heating temperature of the second heating part 5 is lower than the melting temperature of the solder paste 3, and the heating temperature of the first heating part 4 is not lower than the melting temperature of the solder paste 3. In the second heating stage S2, the heating temperatures of the first heating part 4 and the second heating part 5 both exceed the melting temperature of the solder paste 3.

[0030] In this embodiment, the first heating unit 4 is a heating plate, and the second heating unit 5 is a hot air heating unit. The second heating unit 5 is located on the side of the substrate 2 where the solder paste 3 to be melted is disposed. Figure 3 As shown, the first heating part 4 of this embodiment is located at the lower side of the substrate 2 , the solder paste 3 is arranged on the upper side of the substrate 2 , and the second heating part 5 is located above the solder paste 3 .

[0031] The temperature curves of the first heating unit 4 and the second heating unit 5 in the first heating stage S1 and the second heating stage S2 of this embodiment are shown in the attached Figure 4As shown. In the first heating stage S1, the heating temperature of the first heating part 4 is greater than the melting temperature of the solder paste 3, and the side of the solder paste 3 close to the first heating part 4 begins to melt, while the side of the solder paste 3 close to the second heating part 5 does not melt under the action of the hot air whose temperature is lower than the melting point of the solder paste. Preferably, the temperature of the hot air is close to but slightly lower than the melting point of the solder paste, so that the bubbles generated in the melting of the solder paste 3 can slowly gather upward from the bottom; in the second heating stage S2, the heating temperatures of the first heating part 4 and the second heating part 5 are both higher than the melting point of the solder paste 3, and the bubbles generated in the solder paste 3 can be discharged from the surface of the melted solder paste 3, and then the temperatures of the first heating part 4 and the second heating part 5 are both lowered, so that the bubbles in the solder joint formed after cooling can be effectively reduced.

[0032] The hot air heating part (second heating part 5) of this embodiment includes a plurality of hot air nozzles 51 arranged toward the solder paste 3, a wind chamber 52 connected to the hot air nozzles 51, and a high-temperature fan 53 connected to the wind chamber 52, and at least one heater 54 is arranged in the wind chamber 52. It also includes a cooling part that can cool down the hot air of the hot air heating part. The cooling part includes a cold air channel 61 connected to the wind chamber 52 and a cooling fan 62 connected to the cold air channel 61, and a heat exchanger 63 for cooling is arranged in the cold air channel 61. The distance that the hot air is blown out can be controlled by setting the air volume of the hot air heating part to control the blowing distance, so as to achieve the purpose of layered heating without interfering with the temperature of the bottom plate. The cooling part can quickly adjust the upper hot air temperature, so as to achieve rapid adjustment of the wind temperature to ensure that the surface of the solder paste 3 is finally melted.

[0033] As a preferred implementation of this embodiment, at least one return air hole 64 is also provided around each hot air nozzle 51, and the return air hole 64 is connected to the negative pressure pipe 65, and the negative pressure pipe 65 can be connected to an exhaust pump or a vacuum pump to maintain a negative pressure state, so that the air blown out by the hot air nozzle 51 to a certain distance is extracted from the return air hole 64 to form a small cycle, and no lateral airflow is generated, so that a better solder joint can be obtained. The substrate 2 of this embodiment preferably adopts a material with good thermal conductivity such as a copper substrate 2, an aluminum substrate 2 and a ceramic substrate 2.

[0034] 5 and 6 show the comparison of the bubbles in the solder joints after soldering using the soldering device of the present invention and soldering using the conventional method. It can be seen that the soldering device of the present invention can effectively reduce the generation of bubbles during the melting of solder paste, and the device of the present invention can reduce the bubble rate from 25% to 10%.

[0035] Embodiment 2:

[0036] This embodiment is a method for reducing solder bubbles in a semiconductor packaging process, wherein a first heating unit and a second heating unit are respectively arranged on the upper and lower sides of a substrate to be soldered, wherein the first heating unit is a heating plate, and the second heating unit is a hot air heating unit, which melts the solder paste by blowing hot air toward the solder paste. Preferably, the heating plate is arranged in contact with the lower surface of the substrate.

[0037] The method of this embodiment includes at least a first heating stage S1 and a second heating stage S2 in the heating and melting process of the solder paste. The heating temperature of the first heating part in the first heating stage S1 is not less than the melting temperature of the solder paste. The heating temperature of the second heating part in the first heating stage S1 does not exceed the melting temperature of the solder paste but is close to the melting temperature of the solder paste. The heating temperatures of the first heating part and the second heating part in the second heating stage S2 both exceed the melting temperature of the solder paste. The heating temperature of the second heating part does not exceed the heating temperature of the first heating part. For the curves of the wind temperature (T1) and the heating temperature (T3) of the second heating part of this embodiment, see the attached Figure 4 Preferably, the heating temperature T3 of the first heating part is the sum of the melting point (T2) of the solder paste and Tx, and Tx can be set according to the requirements of the furnace temperature curve of the actual product.

[0038] The method of this embodiment uses bottom contact heat transfer and upper hot air heating to gradually melt the solder paste from the bottom to the top, thereby slowly gathering the bubbles upward and quickly expelling the bubbles in the second heating stage S2, thereby forming a good solder joint and effectively reducing the generation rate of bubbles in the solder joint.

[0039] The above implementation modes are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A soldering device with low bubble generation rate for semiconductor packaging, used for soldering a soldering element to a substrate, characterized in that: The device comprises a first heating part located at the lower side of the substrate and a second heating part located at the upper side of the substrate. The device can realize staged heating when melting solder paste. In the first heating stage, the heating temperature of the second heating part is lower than the melting temperature of the solder paste, and the heating temperature of the first heating part is not lower than the melting temperature of the solder paste. In the second heating stage, the heating temperatures of the first heating part and the second heating part both exceed the melting temperature of the solder paste. The second heating part is a hot air heating part, which includes a plurality of hot air nozzles arranged toward the solder paste, at least one return air hole is arranged around each of the hot air nozzles, and also includes a negative pressure pipe connected to the return air hole. The cooling unit is further provided to cool down the hot air from the hot air heating unit.

2. The soldering device with low bubble generation rate for semiconductor packaging according to claim 1, characterized in that: At least one of the first heating part and the second heating part is heated by hot air, and the hot air can be blown toward the solder paste located on the substrate.

3. The soldering device with low bubble generation rate for semiconductor packaging according to claim 2, characterized in that: The first heating part is a heating plate, and the second heating part is located on a side of the substrate where the solder paste to be melted is disposed.

4. The soldering device with low bubble generation rate for semiconductor packaging according to claim 3, characterized in that: The hot air heating unit further includes a wind chamber connected to the hot air nozzle and a high-temperature blower connected to the wind chamber, and at least one heater is disposed in the wind chamber.

5. The soldering device with low bubble generation rate for semiconductor packaging according to claim 4, characterized in that: The cooling unit includes a cold air channel communicated with the air chamber and a cooling fan connected to the cold air channel. A heat exchanger for cooling is arranged in the cold air channel.

6. A method for reducing solder bubbles in a semiconductor packaging process, characterized in that: A first heating unit is respectively arranged on the lower side of the substrate, and a second heating unit is arranged on the upper side. The heating and melting process of the solder paste includes at least a first heating stage and a second heating stage. The heating temperature of the first heating unit in the first heating stage is not less than the melting temperature of the solder paste, and the heating temperature of the second heating unit in the first heating stage is less than the melting temperature of the solder paste. The heating temperatures of the first heating unit and the second heating unit in the second heating stage both exceed the melting temperature of the solder paste. The second heating unit is a hot air heating unit, which includes a plurality of hot air nozzles arranged toward the solder paste, at least one return air hole is also arranged around each of the hot air nozzles, a negative pressure duct connected to the return air hole, and a cooling unit capable of cooling the hot air from the hot air heating unit.

7. The method for reducing solder bubbles in a semiconductor packaging process according to claim 6, characterized in that: The first heating part is a heating plate, and the second heating part heats the solder paste by hot air.

8. The method for reducing solder bubbles in a semiconductor packaging process according to claim 7, characterized in that: The heating temperature of the second heating part does not exceed the heating temperature of the first heating part.

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