A solder ball welding method and its application

Abstract

The present invention discloses a solder ball welding method and its application. The method includes: setting a solder ball on a substrate ball pad, and melting the solder ball by heating a preset part of the solder ball to achieve welding with the substrate ball pad; wherein, controlling the preset part to be located in an area outside the part of the solder ball in contact with the substrate ball pad; and the application of the above solder ball welding method in a ball grid array packaging method and an integrated circuit packaging method can achieve: on the basis of achieving excellent welding between the solder ball (such as a tin ball) and the package substrate, it can avoid the problems of product deformation and reduced service life that may be caused by the existing reflow soldering method, and can further reduce the solder ball pitch and almost even completely avoid the phenomenon of bridging between solder balls.

Description

Technical Field

[0001] The present invention relates to the technical field of ball grid array (BGA) packaging, and particularly relates to a solder ball welding method and its application. Background Art

[0002] BGA (Ball Grid Array) packaging, that is, ball grid array packaging, is to fabricate an array of solder balls (common solder balls can be, for example, tin balls) at the bottom of the package substrate as the I / O terminals of the circuit to be interconnected with a printed circuit board (PCB). Currently, the welding method of this array of solder balls usually uses reflow soldering. However, in actual operation, the obtained BGA products are inevitably prone to deformation. And when there are more requirements for products, such as more I / O terminals, it is difficult to reduce the solder ball pitch. If the ball pitch is forced to be reduced, bridging between solder balls is likely to occur. In addition, the service life of the products is also affected to a certain extent, and there may even be an obvious phenomenon of a decrease in the service life of some products. Summary of the Invention

[0003] The object of the present invention is to overcome the deficiencies of the prior art and provide a new solder ball welding method, which can be used in ball grid array packaging operations. On the basis of achieving excellent welding between the solder balls (such as tin balls) and the package substrate, it can avoid problems such as product deformation and decreased service life that may be caused by the existing reflow soldering method, and can further reduce the solder ball pitch and hardly even completely avoid the bridging phenomenon between solder balls.

[0004] The present invention also provides a ball grid array packaging method using the above solder ball welding method.

[0005] The present invention also provides an integrated circuit packaging method using the above solder ball welding method.

[0006] To achieve the above object, a technical solution adopted by the present invention is:

[0007] A solder ball welding method, which includes: arranging solder balls on the ball pads of the substrate for ball implantation, and heating a preset part of the solder balls to melt the solder balls and achieve welding with the ball pads of the substrate; wherein, it is controlled that the preset part is located in a region outside the part of the solder ball in contact with the ball pads of the substrate.

[0008] According to some preferred aspects of the present invention, the heating method is heat conduction.

[0009] Furthermore, the heat conduction method is achieved by the heating component coming into contact with the preset part of the solder ball to transfer heat.

[0010] According to some preferred aspects of the present invention, the time for controlling heating until the solder ball melts is 5 - 100 s, more preferably 15 - 80 s. In some specific embodiments of the present invention, the time for controlling heating until the solder ball melts is 5 - 10 s, or 11 - 20 s, or 21 - 30 s, or 31 - 40 s, or 41 - 50 s, or 51 - 60 s, or 61 - 70 s, or 71 - 80 s, or 81 - 90 s, or 91 - 100 s.

[0011] According to some preferred aspects of the present invention, during the heating process, the solder ball and the substrate ball pad are controlled to be arranged from top to bottom in sequence.

[0012] Further, the preset part is located at the top of the solder ball.

[0013] According to some preferred aspects of the present invention, during the heating process, the heating steps include:

[0014] First, a first heating component with a first cross-sectional area at the bottom is brought into contact with the surface of the preset part to heat the solder ball until the solder ball melts;

[0015] Then, after the solder ball melts or during the melting process of the solder ball, a second heating component with a second cross-sectional area is inserted into the solder ball;

[0016] Remove the first heating component and the second heating component;

[0017] Wherein, the first cross-sectional area is larger than the second cross-sectional area.

[0018] Further, the second cross-sectional area is smaller than the surface area of the preset part.

[0019] Further, the length of the second heating component inserted into the solder ball is greater than or equal to 0.25 times the diameter of the solder ball and less than or equal to 0.75 times the diameter of the solder ball.

[0020] Further, the heating time for controlling the first heating component to heat the solder ball until the solder ball melts is 5 - 100 s, and the first heating component and the second heating component are removed after 1 - 20 s when the second heating component is inserted into the solder ball.

[0021] Further, during the heating process, the following heating mechanism is used for heating:

[0022] The heating mechanism includes a heat source, the first heating component and the second heating component that respectively transfer heat to the heat source by heat conduction.

[0023] According to some preferred aspects of the present invention, the second heating component conducts heat with the heat source through the first heating component.

[0024] According to some preferred aspects of the present invention, a receiving groove is formed inside the first heating component, and the second heating component is located inside the receiving groove and is slidably arranged relative to the receiving groove.

[0025] According to some preferred aspects of the present invention, the heating mechanism further includes an elastic member that tends to make the second heating component slide relative to the receiving groove.

[0026] According to some preferred aspects of the present invention, the telescopic direction of the elastic member is parallel to the extending direction of the receiving cavity.

[0027] According to some preferred aspects of the present invention, the elastic member is arranged inside the receiving groove.

[0028] According to some preferred aspects of the present invention, the first heating components and the second heating components are respectively multiple and have the same quantity, and one first heating component corresponds to one second heating component.

[0029] According to some preferred aspects of the present invention, the shortest distance between the preset portion and the surface of the substrate ball grid pad is greater than the radius of the solder ball.

[0030] According to some preferred aspects of the present invention, the preset portion and the portion of the solder ball in contact with the substrate ball grid pad are arranged opposite to each other in the up and down direction.

[0031] According to some preferred aspects of the present invention, the surface area of the preset portion is 1 / 100 - 1 / 10 of the spherical surface area of the solder ball; more preferably, the surface area of the preset portion is 1 / 50 - 1 / 20 of the spherical surface area of the solder ball.

[0032] According to some specific aspects of the present invention, the solder ball is a tin ball.

[0033] According to some preferred aspects of the present invention, there are multiple solder balls and they are arranged in an array, the number of the substrate ball grid pads corresponds to the number of the solder balls one by one, and by independently heating the preset portions of each solder ball respectively, each solder ball is melted respectively and the welding with the corresponding substrate ball grid pad is realized.

[0034] Another technical solution provided by the present invention: a ball grid array packaging method, which includes the solder ball welding method described above.

[0035] Another technical solution provided by the present invention: An integrated circuit packaging method, which includes the solder ball welding method or the ball grid array packaging method described above.

[0036] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0037] The solder ball welding method of the present invention innovatively adopts a targeted single-point heating method. Further, a specific area (i.e., the preset part) of the solder ball is selected for heating, and it is controlled that the preset part is located at a position outside the part of the solder ball in contact with the substrate ball pads. Such an operation greatly avoids the problem that the substrate may be deformed due to excessive heat during the process of heating and melting the solder ball and realizing the welding with the substrate ball pads, reduces the amplitude and frequency of the passive temperature rise and fall of the substrate, can further shorten the solder ball pitch of the BGA product, reduce or even avoid the solder joint offset and the bridging phenomenon between the solder balls, achieve a smaller size, higher quality of the product, can add more I / O terminals, and moreover, the method of the present invention can also reduce the solder ball welding station fixtures, is simple to operate, saves costs, can improve production capacity, improve the qualified rate of the product, and extend the service life of the product. Description of the Drawings

[0038] Figure 1 It is a working schematic diagram of soldering the solder balls by reflow soldering in the current ball grid array packaging;

[0039] Figure 2 It is a schematic diagram of the deformation mode and deformation process of the substrate after soldering the solder balls by reflow soldering in the current ball grid array packaging;

[0040] Figure 3 It is a schematic diagram of the state where the heating mechanism heats the solder ball in the embodiment of the present invention;

[0041] Figure 4 For Figure 3 The enlarged schematic diagram of part A in;

[0042] Figure 5 It is a schematic diagram of the second heating component inserted into the solder ball after the solder ball melts or during the melting process of the solder ball in the embodiment of the present invention;

[0043] Figure 6 For Figure 5 The enlarged schematic diagram of part B in;

[0044] Figure 7 It is a schematic diagram of the heating mechanism disengaging from the solder ball in the embodiment of the present invention;

[0045] Figure 8 For Figure 7 The enlarged schematic diagram of part C in;

[0046] Figure 9 Schematic diagram of the heating mechanism moving away from the solder balls after soldering in the embodiments of the present invention;

[0047] Figure 10 is Figure 9 an enlarged schematic diagram of position D in

[0048] wherein, 1, substrate; 2, solder ball; 31, heat source; 32, first heating component; 33, second heating component; 34, elastic member. Detailed implementation manners

[0049] Currently, generally, the reflow soldering method is used for soldering the solder balls and the ball pads of the package substrate in the ball grid array package (the ball pads are arranged on the substrate). However, in actual operation, the obtained BGA products are inevitably deformed (such as substrate deformation). And with the increasing demand for products, such as more I / O terminals, it is difficult to reduce the pitch of the solder balls. If the pitch is forced to be reduced, bridging between the solder balls is likely to occur. In addition, the service life of the products is also affected to a certain extent, and even the service life of some products may decrease significantly.

[0050] The inventors of the present invention found in the long-term practice process that the above problems should be due to the fact that the reflow soldering method makes the environmental temperature of the products too high, so that the whole product will experience high temperature changes. And the high environmental temperature is likely to cause deformation of the substrate in the product. Moreover, during the working process of reflow soldering, the substrate will even be deformed multiple times in the changing temperature ( Figure 1 An exemplary working schematic diagram of soldering the solder balls in the current ball grid array package by reflow soldering is given. Figure 2It is a schematic diagram of the possible deformation modes and deformation processes of the substrate after the solder balls in the current ball grid array package are welded by reflow soldering. Especially for products with defects that need to be reworked, they will experience multiple high and low temperature changes, which will cause the substrate to warp, possibly resulting in poor soldering. Moreover, it may also cause the displacement and possible approach of two or more adjacent solder balls that are already arranged in an array, resulting in bridging between the melted solder balls. Especially when more I / O terminals are required, it is difficult to reduce the solder ball pitch, because reducing the ball pitch means that the solder balls are more likely to approach and bridge when the substrate warps during the reflow soldering process. At the same time, due to the characteristics of reflow soldering, air or nitrogen is heated to a sufficiently high temperature and then blown onto the substrate on which the solder balls have been placed, which causes the substrate to directly receive too much heat, resulting in, for example, aging or other adverse changes, and reducing the service life of the product to a certain extent. Therefore, based on the above findings, in the process of continuous experimentation and experience summary, the inventor of the present invention innovatively proposed to adopt a targeted single-point heating method, specifically, directly and independently heating a specific area of the solder ball, rather than heating the solder ball through the ambient temperature or high-temperature air flow. This targeted heating method is to only heat the preset part of the solder ball that is not in contact with the substrate ball pads. In other words, in this heating method, the substrate can basically only be heated by the heat transfer of the solder ball. To put it another way, most of the heat received by the substrate comes from the heat transfer of the solder ball. When the solder ball absorbs heat and melts to complete the soldering, the substrate is limited in heat absorption, effectively avoiding obvious and frequent temperature changes of the substrate. Moreover, this method has a higher heating efficiency for the solder ball and can achieve soldering in a shorter time, further avoiding the warping and deformation phenomenon that may be caused by the passive temperature rise and fall of the substrate, thus effectively solving the adverse effects that may occur when soldering solder balls by reflow soldering.

[0051] According to one embodiment, the heating method used to heat the preset part of the solder ball can be heat conduction. By directly contacting between objects, a large number of molecular thermal motions in the substance collide with each other, so that energy is transferred from the high-temperature part of the object to the low-temperature part, or from the high-temperature object to the low-temperature object. Further, the heat transfer is realized by contacting the heating component with the preset part of the solder ball. This method further reduces the possibility that the heat for heating the solder ball overflows outward and causes the ambient temperature to change too much and affect the substrate.

[0052] According to one embodiment, the time for controlling heating until the solder ball melts is preferably such that the solder ball can be melted quickly but without significantly changing the ambient temperature (i.e., reducing the temperature affecting the substrate). Generally, the time for controlling heating until the solder ball melts is 5 - 100 s, more preferably 15 - 80 s. Specifically, for example, the time for controlling heating until the solder ball melts can be 5 - 10 s, or 11 - 20 s, or 21 - 30 s, or 31 - 40 s, or 41 - 50 s, or 51 - 60 s, or 61 - 70 s, or 71 - 80 s, or 81 - 90 s, or 91 - 100 s.

[0053] According to one embodiment, the preset part and the part of the solder ball in contact with the substrate ball pad are arranged oppositely in the up - down direction. Preferably, during the heating process, it is preferred to control the solder ball and the substrate ball pad to be arranged from top to bottom in sequence, that is, it can enable the solder ball to be stably supported on the substrate ball pad with less or even no external force, while also facilitating heating and reducing the possibility of the solder ball shifting due to the heating operation. Further, it is preferred to control the preset part to be located at the top of the solder ball. In this way, contact heating of the solder ball can be carried out from above. When the heating component is removed, the solder ball can be less affected by the heating component under the action of its own gravity. In some specific embodiments, the surface area of the preset part is 1 / 100 - 1 / 10 of the spherical surface area of the solder ball; more preferably, the surface area of the preset part is 1 / 50 - 1 / 20 of the spherical surface area of the solder ball, reducing the influence of the contact between objects after heating by heat conduction on the shape of the melted solder ball.

[0054] According to one embodiment, during the heating process, the heating steps include:

[0055] First, use a first heating component with a first cross - sectional area at the bottom to contact the surface of the preset part to heat the solder ball until it melts;

[0056] Then, after the solder ball melts or during the melting process of the solder ball, insert a second heating component with a second cross - sectional area into the solder ball;

[0057] Remove the first heating component and the second heating component;

[0058] Among them, the first cross-sectional area is larger than the second cross-sectional area, and the first heating component with a larger cross-sectional area at the bottom can have more contact with the preset part of the solder ball to achieve rapid heat transfer and accelerate the melting of the solder ball; and the second heating component needs to be inserted into the solder ball. The purpose is: when the bottom of the first heating component is out of contact with the preset part of the solder ball, due to the interaction force between the two, the molten solder ball may be deformed or even out of its original position during the removal of the first heating component. At this time, the second heating component inserted into the solder ball can stabilize the solder ball.

[0059] Generally, the second heating component can be pulled out of the solder ball while the first heating component is removed, that is, the second heating component can be removed at the same time as the first heating component, but the second heating component will lag behind the first heating component in separating from the solder ball; the first heating component can also be removed first, and then the second heating component can be removed. At the same time, since the second heating component needs to be inserted into the solder ball, it is preferred that the second cross-sectional area is smaller than the surface area of ​​the preset part, that is, the contact area between the second heating component and the solder ball is reduced as much as possible, reducing its own influence on the solder ball; in addition, the length of the second heating component inserted into the solder ball is controlled to be greater than or equal to 0.25 times the diameter of the solder ball and less than or equal to 0.75 times the diameter of the solder ball.

[0060] Furthermore, the action of inserting the second heating component into the solder ball can be that the second heating component is inserted into the solder ball after it is melted or in the process of melting under the action of gravity relying on its own gravity, or it can be inserted into the solder ball after it is melted or in the process of melting under the independent or coordinated action of other external forces.

[0061] According to one embodiment, during the heating process, the following heating mechanism is used for heating:

[0062] The heating mechanism includes a heat source, a first heating component and a second heating component that transfer heat to the heat source through heat conduction respectively. The second heating component conducts heat to the heat source through the first heating component. Further, it can be arranged as follows: a receiving groove is formed inside the first heating component, and the second heating component is located in the receiving groove and is arranged to be slidable relative to the receiving groove. In this way, on the one hand, the second heating component can conduct heat to the heat source through the first heating component; on the other hand, after the first heating component heats the solder ball and melts the solder ball or during the melting process, the second heating component can slide relative to the first heating component and extend out of the receiving groove and then insert into the solder ball. When the first heating component is withdrawn after heating, the second heating component is inserted into the solder ball and plays a role in stabilizing the shape of the molten solder ball. In fact, in the early stage of this setting method, the second heating component can also conduct heat to the solder ball, increasing the speed and efficiency of heat transfer, accelerating the melting speed of the solder ball, and at the same time reducing the amount of heat overflowing outward. Of course, preferably, a protective layer can be provided outside the first heating component, only leaving the part in contact with the solder ball at the lower part exposed, and enabling the second heating component to slide out of the receiving groove, further ensuring the effect of heating the solder ball and reducing the influence of heat overflow on the ambient temperature and even the temperature of the substrate.

[0063] Further, the heating mechanism further includes an elastic member that tends to make the second heating component slide relative to the receiving groove. The elastic member is arranged in the receiving groove, and the telescopic direction of the elastic member is parallel to the extending direction of the receiving cavity. In this way, when the first heating component heats and melts the solder ball, the second heating component can quickly insert into the solder ball under the action of the elastic member, which can reduce the adverse situation that may affect the shape of the solder ball caused by slow insertion.

[0064] In fact, during the ball grid array packaging process, there are multiple solder balls and they are arranged in an array. The number of substrate ball pads for ball implantation corresponds one-to-one with the number of solder balls. By separately and independently heating a preset part of each solder ball, each solder ball can be melted respectively and welded to the corresponding substrate ball pad. Therefore, there are multiple first heating components and second heating components respectively, and the numbers are the same. One first heating component corresponds to one second heating component, that is, each solder ball can be heated at a single point simultaneously and separately.

[0065] Generally, during the ball grid array packaging process, the solder balls are usually tin balls. The composition of the tin balls can be, for example: Sn63 / Pb37 (indicating an alloy solder bar with a tin content of 63% and a lead content of 37%, and the meaning of the numbers listed after each component is the same in the following), Sn62 / Pb36 / Ag2, Sn99.3 / Cu0.7, Sn96.5 / Ag3.5, Sn96 / Ag4, Sn96.5 / Ag3 / Cu0.5, etc.

[0066] Such asFigures 3 - 10 As shown, a schematic diagram of a process of the solder ball welding method of the present invention is exemplarily given. Specifically, as Figures 3 - 4 shown, after solder balls 2 are placed on each substrate ball pads (not shown) on substrate 1 (preferably, a soldering flux that can remove surface oxides can be sprayed before placing the solder balls 2, and the soldering flux includes but is not limited to: rosin, organic acids, inorganic salts, organic halides, etc.), with the solder balls 2 on top and the substrate ball pads below, by moving the heating mechanism, both the first heating component 32 and the second heating component 33 directly contact a preset portion at the top of the spherical surface of the solder balls 2, thereby achieving heat transfer heating. Among them, Figure 3 FIG. is a schematic diagram of the heating mechanism heating each solder ball on the heating substrate simultaneously, Figure 4 is Figure 3 an enlarged schematic diagram at A in FIG., the length and width of the bottom of the first heating component 32 can be 4 / 3 - 2 / 3 of the solder ball radius; as Figures 5 - 6 shown, after the bottom of the first heating component 32 contacts the preset portion of the solder ball 2 for heat transfer for about 5 - 100 s, the second heating component 33 is inserted into the solder ball 2 under the combined action of gravity and the elastic member 34. Among them, Figure 5 FIG. is a schematic diagram of the action relationship between each component of the heating mechanism and the solder ball 2 at this time, Figure 6 is Figure 5 an enlarged schematic diagram at B in FIG.; as Figures 7 - 8 shown, after the second heating component 33 is inserted into the solder ball 2 for about 1 - 20 s, the heating mechanism moves upward to separate from the solder ball 2, and the welding is completed. During this process, the first heating component 32 separates from the preset heating portion first, and the second heating component 33 gradually withdraws from the inside of the solder ball 2. Among them, Figure 7 FIG. is a schematic diagram of the action relationship between each component of the heating mechanism and the solder ball 2 at this time, Figure 8 is Figure 7 an enlarged schematic diagram at C in FIG.; as Figures 9 - 10 shown, these figures exemplify a schematic diagram of the heating mechanism moving away from the solder ball 2 after the solder ball 2 is welded (wherein, Figure 9 FIG. is a schematic diagram of the action relationship between each component of the heating mechanism and the solder ball 2 at this time, Figure 10 is Figure 9 an enlarged schematic diagram at D in FIG.), and moreover, the second heating component 33 can be completely received into the receiving groove (not shown) of the first heating component 31. The receiving method can be that under the action of an external force, it gradually overcomes gravity and the elastic force of the elastic member 34 and slides into the receiving groove. Preferably, it is maintained that the bottom of the first heating component 32 is flush with the bottom of the second heating component 33, that is, a locking component can be set to keep this state, and before the next use, it can be unlocked after contacting the solder ball 2.

[0067] In this field, due to reasons such as the wettability between the solder balls and the ball pads for ball implantation, as Figures 3 - 10 shown, the solder balls still present a roughly spherical or spherical-like state before and after heating and after welding with the ball pads for ball implantation.

[0068] The above solder ball welding method can be applied to the ball grid array packaging method and the integrated circuit packaging method and achieve the expected effects, overcoming some defects existing in the existing reflow soldering.

[0069] The following further illustrates the above solution with specific embodiments; it should be understood that these embodiments are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited by the scope of the following embodiments; the implementation conditions adopted in the embodiments can be further adjusted according to specific requirements.

[0070] Embodiment 1

[0071] This example provides a solder ball welding method. The solder ball is a tin ball, and the method includes:

[0072] (1) Flip the product with the solder balls to be welded as the I / O terminals of the circuit, so that the substrate ball pads on the package substrate face upward. Use the spraying method to spray flux on the ball surfaces of the substrate ball pads, and then place the tin balls one by one on each substrate ball pad. The composition of the tin balls is: Sn63 / Pb37 (indicating an alloy solder bar with a tin content of 63% and a lead content of 37%);

[0073] (2) Select a partial area at the top of the tin ball as the preset part to be heated. Use the above heating mechanism to heat the selected preset part. Set the heating mechanism above the tin ball and make the bottom of the first heating component basically cover the surface of the preset part. When heating is required, move the heating mechanism downward. In this example, by controlling the surface area of the preset part and the temperature of the heat source, the tin ball is roughly completely melted in about 30s. During the melting process of the tin ball, the second heating component extends downward into the tin ball under the action of gravity and the elastic member. The length of the second heating component inserted into the solder ball is about the radius of the solder ball;

[0074] (3) After about 5s when the action of the second heating component inserted into the tin ball is completed, move the mechanism upward to separately disengage the first heating component and the second heating component from the tin ball, and the welding is completed.

[0075] Embodiment 2

[0076] This example provides a solder ball welding method. The solder ball is a tin ball, and the method includes:

[0077] (1)Flip the product with the solder balls to be welded as the I / O terminals of the circuit, so that the substrate ball pads on the package substrate face upward. Use the spraying method to spray flux on the ball planting surfaces of the substrate ball pads, and then place solder balls one by one on each substrate ball pad. The composition of the solder balls is Sn63 / Pb37 (an alloy solder bar with 63% tin content and 37% lead content);

[0078] (2)Select a partial area at the top of the solder ball as the preset part to be heated, and use the above heating mechanism to heat the selected preset part. Set the heating mechanism above the solder ball, and make the bottom of the first heating component basically cover the surface of the preset part. When heating is required, move the heating mechanism downward. In this example, by controlling the surface area of the preset part and the temperature of the heat source, the solder ball is roughly completely melted in about 35 s. During the melting process of the solder ball, the second heating component extends downward into the solder ball under the action of gravity and the elastic component. The length of the second heating component inserted into the solder ball is about the radius of the solder ball;

[0079] (3)About 8 s after the action of the second heating component inserted into the solder ball is completed, move the mechanism upward to separate the first heating component and the second heating component from the solder ball successively, and the welding is completed.

[0080] Example 3

[0081] This example provides a solder ball welding method. The solder ball is a tin ball, and the method includes:

[0082] (1)Flip the product with the solder balls to be welded as the I / O terminals of the circuit, so that the substrate ball pads on the package substrate face upward. Use the spraying method to spray flux on the ball planting surfaces of the substrate ball pads, and then place solder balls one by one on each substrate ball pad. The composition of the solder balls is Sn63 / Pb37 (an alloy solder bar with 63% tin content and 37% lead content);

[0083] (2)Select a partial area at the top of the solder ball as the preset part to be heated, and use the above heating mechanism to heat the selected preset part. Set the heating mechanism above the solder ball, and make the bottom of the first heating component basically cover the surface of the preset part. When heating is required, move the heating mechanism downward. In this example, by controlling the surface area of the preset part and the temperature of the heat source, the solder ball is roughly completely melted in about 40 s. During the melting process of the solder ball, the second heating component extends downward into the solder ball under the action of gravity and the elastic component. The length of the second heating component inserted into the solder ball is about the radius of the solder ball;

[0084] (3)About 10 s after the action of the second heating component inserted into the solder ball is completed, move the mechanism upward to separate the first heating component and the second heating component from the solder ball successively, and the welding is completed.

[0085] Example 4

[0086] This example provides a solder ball welding method. The solder ball is a tin ball, and the method includes:

[0087] (1) Flip the product with the solder balls to be welded as the I / O terminals of the circuit, so that the substrate ball pads on the package substrate face upward. Use the spraying method to spray flux on the ball surfaces of the substrate ball pads, and then place solder balls one by one on each substrate ball pad. The composition of the solder balls is Sn63 / Pb37 (indicating an alloy solder bar with a tin content of 63% and a lead content of 37%);

[0088] (2) Select a partial area at the top of the solder ball as the preset part to be heated. Use the above heating mechanism to heat the selected preset part. Set the heating mechanism above the solder ball, and make the bottom of the first heating component able to basically cover the surface of the preset part. When heating is required, move the heating mechanism downward. In this example, by controlling the surface area of the preset part and the temperature of the heat source, the solder ball is roughly completely melted in about 50 s. During the melting process of the solder ball, the second heating component extends downward into the solder ball under the action of gravity and the elastic member. The length of the second heating component inserted into the solder ball is about the radius of the solder ball;

[0089] (3) About 10 s after the action of inserting the second heating component into the solder ball is completed, move the mechanism upward to separately disengage the first heating component and the second heating component from the solder ball, and the welding is completed.

[0090] Test the product with the solder balls welded as above. The results show that there is no bridging phenomenon between the welded solder balls, and the solder ball solder joints are hardly offset, indicating that the solder ball pitch can be further reduced or the product size can be reduced, and more I / O terminals can be added. Almost no solder ball welding station fixture is used in the whole process, the operation is simple, the cost is saved, and at the same time, the size, height and quality of the solder balls meet the expectations.

[0091] The above examples are only for illustrating the technical concept and features of the present invention, and the purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A solder ball welding method, comprising: placing a solder ball on a substrate ball pad, characterized in that the solder ball welding method further comprises: heating a preset portion of the solder ball to melt the solder ball and achieve welding with the substrate ball pad; wherein, controlling the preset portion to be located in a region outside the portion of the solder ball in contact with the substrate ball pad; during the heating process, controlling the solder ball and the substrate ball pad to be arranged from top to bottom in sequence, and the preset portion is located at the top of the solder ball; during the heating process, the heating step comprises: first, using a first heating member having a first cross-sectional area at the bottom to contact the surface of the preset portion to heat the solder ball until the solder ball melts; then, after the solder ball melts or during the melting process of the solder ball, inserting a second heating member having a second cross-sectional area into the solder ball; removing the first heating member and the second heating member, and the second heating member lags behind the first heating member to disengage from the solder ball; wherein, the first cross-sectional area is greater than the second cross-sectional area.

2. The solder ball welding method according to claim 1, characterized in that the heating method is heat conduction, and the heat conduction method is to achieve heat transfer by contacting the heating member with the preset portion of the solder ball.

3. The solder ball welding method according to claim 1, characterized in that the time for controlling heating until the solder ball melts is 5 - 100 s.

4. The solder ball welding method according to claim 3, characterized in that the time for controlling heating until the solder ball melts is 15 - 80 s.

5. The solder ball welding method according to claim 1, characterized in that the shortest distance between the preset portion and the surface of the substrate ball pad is greater than the radius of the solder ball.

6. The solder ball welding method according to claim 1, characterized in that the surface area of the preset portion is 1 / 100 - 1 / 10 of the spherical surface area of the solder ball.

7. The solder ball welding method according to claim 6, characterized in that the surface area of the preset portion is 1 / 50 - 1 / 20 of the spherical surface area of the solder ball.

8. The solder ball welding method according to claim 1, characterized in that the second cross-sectional area is smaller than the surface area of the preset portion.

9. The solder ball welding method according to claim 1, characterized in that the length of the second heating member inserted into the solder ball is greater than or equal to 0.25 times the diameter of the solder ball and less than or equal to 0.75 times the diameter of the solder ball.

10. The solder ball welding method according to claim 1, characterized in that the heating time for controlling the first heating member to heat the solder ball until the solder ball melts is 5 - 100 s, and the first heating member and the second heating member are removed after 1 - 20 s after the second heating member is inserted into the solder ball.

11. The solder ball welding method according to claim 1, characterized in that during the heating process, the following heating mechanism is used for heating: The heating mechanism includes a heat source, a first heating component and a second heating component that respectively transfer heat to the heat source by heat conduction; wherein, the second heating component conducts heat to the heat source through the first heating component; a receiving groove is formed inside the first heating component, and the second heating component is located in the receiving groove and is slidably arranged relative to the receiving groove; the heating mechanism further includes an elastic member that tends to make the second heating component slide relative to the receiving groove, the elastic member is arranged in the receiving groove, and the telescopic direction of the elastic member is parallel to the extending direction of the receiving cavity; the first heating component and the second heating component each have a plurality of them and the same number, and one first heating component corresponds to one second heating component.

12. The solder ball welding method according to claim 1, characterized in that, the solder ball is a tin ball.

13. The solder ball welding method according to claim 1, characterized in that, the solder balls are multiple and are arranged in an array, the number of substrate ball pads for ball implantation corresponds one-to-one to the number of solder balls, and by independently heating the preset parts of each solder ball, each solder ball is melted respectively and the welding with the corresponding substrate ball pad for ball implantation is realized.

14. A ball grid array packaging method, characterized in that, the ball grid array packaging method includes the solder ball welding method according to any one of claims 1-13.

15. An integrated circuit packaging method, characterized in that, the integrated circuit packaging method includes the solder ball welding method according to any one of claims 1-13 or the ball grid array packaging method according to claim 14.

Images