A CBGA column implanting device and a column implanting method

Abstract

The application provides a CBGA column implanting device and a column implanting method, and solves the technical problem that replacing the solder ball with a spring column is not only complicated to operate, but also causes the spring column to be misaligned or easily fall off, etc.The application fixes the CBGA device without the solder ball, then prints solder paste on the pad of the CBGA device by using a small steel mesh or a tin paste jet printing machine, then places the spring column according to the 1:1 (i.e., in situ) pad position of the CBGA device, and fixes the CBGA device body and the spring column by using a pressing block, and finally welds the spring column to the self pad of the CBGA device by using a welding device, so that the replacement of the solder ball of the CBGA device is realized.

Description

Technical Field

[0001] This invention belongs to the field of precision electronic assembly technology, and relates to a CBGA column implantation device and column implantation method. Background Technology

[0002] CBGA devices possess excellent thermal and electrical properties, along with good hermeticity and resistance to damp heat, making them widely used in various electronic assembly fields. However, due to the significant difference in the coefficient of thermal expansion (CTE) between the ceramic substrate of CBGA devices and the printed circuit board (PCB) substrate (6 PPM / ℃ for the former and 16 PPM / ℃ to 25 PPM / ℃ for the latter), CBGA solder joints are prone to thermal stress in high and low temperature operating environments. This can lead to solder joint fatigue cracking failure (i.e., the leaded or lead-free solder balls integrated into the CBGA chip are susceptible to fatigue cracking due to thermal stress). Since solder joint fatigue cracking of CBGA devices typically occurs some time after product assembly (usually after 3 years), if CBGA devices are used only in relatively relaxed civilian and consumer applications, this problem generally does not affect the product's functionality. However, if used in demanding aerospace or other high-reliability applications, solder joint fatigue failure of CBGA devices will severely impact the functionality of products in these fields, necessitating the development of appropriate solutions.

[0003] Because spring posts possess both rigidity and flexibility, they can effectively release the shear force caused by the mismatch in thermal expansion coefficients between the CBGA ceramic substrate material and the printed circuit board (PCB) substrate material. Therefore, replacing the solder balls of CBGA devices with spring posts can effectively overcome and alleviate the problem of thermal expansion coefficient mismatch between the CBGA ceramic substrate and the PCB material, significantly improving the thermal fatigue life of the solder joints. However, currently, replacing solder balls with spring posts is usually done manually, lacking corresponding process equipment and method specifications. This not only makes the operation complex but also easily leads to spring post misalignment or detachment, resulting in low replacement efficiency and frequent replacement problems. The replacement method urgently needs improvement. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing methods that replace solder balls with spring pillars, which are not only complex to operate but also prone to spring pillar misalignment or easy detachment. This invention provides a CBGA pillar installation device and method.

[0005] The main concept of this invention is as follows: by designing a spring post fixture, a CBGA device with its own solder balls removed is fixed, and then solder paste is printed on its pads using a small stencil or solder paste printer. Next, spring posts are placed according to the CBGA device pad positions at a 1:1 ratio (i.e., in situ), and pressure blocks are used to fix the CBGA device body and the spring posts. Finally, the spring posts are soldered to the CBGA device's own pads using a soldering device, thereby replacing the solder balls that come with the CBGA device.

[0006] To achieve the above objectives, the technical solution provided by this invention is:

[0007] A CBGA column implantation device, characterized in that it includes a base, an upper mold, and a pressure block for use.

[0008] The base has a hollow area in the middle, the size of which is larger than the CBGA device to be replaced, and the bottom of the base in the hollow area has a step for supporting and limiting the CBGA device to be replaced.

[0009] The upper mold is installed on the upper part of the base, and the position on it corresponding to the hollow area is a slotted area; the thickness of the upper mold in the slotted area is less than the thickness of the upper mold body, and the upper mold in the slotted area is provided with an array of mounting holes for placing the spring pillars to be installed. The array of mounting holes is consistent with the pad arrangement of the CBGA device to be replaced.

[0010] The size of the pressure block is adapted to the slotted area of ​​the upper mold, and the middle part is provided with a through hole array that is consistent with the arrangement of the mounting hole array.

[0011] Furthermore, in order to increase the heat dissipation area, a heat dissipation area is also provided around the hollow area on the base.

[0012] Furthermore, in order to improve heat dissipation efficiency and accelerate flux evaporation, the area on the pressure block where the through-hole array is set is a hollow area.

[0013] Furthermore, the base and the upper mold are mounted together by fasteners, and both the base and the upper mold are provided with fixing holes for mounting the fasteners;

[0014] Furthermore, in order to improve the service life of the column planting device, the base, upper mold and pressure block are all made of high-temperature resistant synthetic stone.

[0015] Furthermore, this invention also provides a method for column implantation using the aforementioned CBGA column implantation device, characterized by the following steps:

[0016] 1) Use a soldering iron to remove the solder balls from the CBGA device;

[0017] 2) Use a soldering iron and desoldering wick to remove any remaining solder from the CBGA device;

[0018] 3) Use a small stencil or solder paste printer to print solder paste on CBGA devices;

[0019] 4) Place the CBGA device with solder paste printed on it on the step in the hollow area of ​​the base of the post-planting device; 5) Install the upper mold of the post-planting device onto the base of the post-planting device.

[0020] 6) Use tweezers (e.g., pointed tweezers) to place the spring posts one by one onto the corresponding pads of the CBGA device through the mounting hole array on the upper mold of the post-planting device;

[0021] 7) Place the pressure block of the column planting device into the slotted area of ​​the upper mold of the column planting device;

[0022] 8) Use a reflow furnace or vapor phase furnace to perform overall furnace welding on the column planting device;

[0023] 9) After welding is completed, disassemble the post-planting device, remove the CBGA device, and clean the CBGA device to complete the post-planting process.

[0024] Furthermore, in step 3), when printing solder paste using a small stencil, the thickness of the stencil is between 0.12mm and 0.15mm, and when printing using a solder paste inkjet printer, the thickness of the solder paste is between 0.15mm and 0.2mm.

[0025] Further, in step 8), when using leaded solder paste for pillar placement, the maximum furnace temperature of the reflow oven or vapor phase furnace should be controlled at 215±5℃, and when using lead-free solder paste for pillar placement, the maximum furnace temperature of the reflow oven or vapor phase furnace should be controlled at 245±5℃.

[0026] Further, in step 9), the CBGA device is cleaned using a 1:1 alcohol-gasoline mixture.

[0027] Furthermore, the spring post can be made of copper.

[0028] The advantages of this invention are:

[0029] 1. This invention provides a CBGA spring post installation device and method, which can accurately replace the leaded or lead-free solder balls that come with the CBGA with spring posts, effectively releasing solder joint stress and improving solder joint fatigue life.

[0030] 2. The CBGA implantation device of the present invention is simple to operate, safe and reliable. When the CBGA device after replacing the spring column is replaced by this implantation device, accelerated testing is carried out. Compared with the CBGA device with built-in solder balls, the resistance to thermal fatigue shock accelerated testing can be improved from 40 cycles to more than 400 cycles, and the thermal fatigue life can be improved by more than 10 times.

[0031] 3. The column planting device provided by the present invention has good air convection and heat dissipation effects, which can effectively reduce solder splatter.

[0032] 4. The column planting device provided by the present invention is simple in design and ingenious in conception. It allows direct visual inspection of the placement and fixation of the CBGA chip and spring column, making inspection convenient.

[0033] 5. The column planting device provided by the present invention has good high temperature resistance, can be reused multiple times, and is economical and environmentally friendly. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the CBGA column implantation device.

[0035] Figure 2 The flowchart shows the CBGA column implantation method.

[0036] Figure 3 The images show a before-and-after comparison of replacing the spring posts on a CBGA device. a is before replacement, and b is after replacement.

[0037] The attached figures are labeled as follows:

[0038] 1-Base, 2-CBGA, 3-Upper mold, 4-Pressure block. Detailed Implementation

[0039] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0040] like Figure 1 As shown, a CBGA column implantation device includes a base 1, an upper mold 3, and a pressing block 4.

[0041] The base 1 is 51mm long, 51mm wide, and 5.2mm high. Mounting holes with a diameter of 5mm are machined at the four corners of the base 1, and fasteners (such as fixing cylinders) are installed there. A rectangular hollow area with dimensions of 15mm x 15mm is machined in the center of the base 1, and a rectangular hollow area with a length of 10mm and a width of 7.5mm is machined on each of the four sides. The hollow areas facilitate operation and are beneficial for increasing the heat dissipation area. A step is machined at the bottom of the base 1 within the central rectangular hollow area to accommodate (and provide support and limit) CBGA chips.

[0042] The upper mold 3 is 51mm long, 51mm wide, and 5.0mm high. Mounting holes with a diameter of 5mm are machined at the four corners of the upper mold 3, corresponding to the fixed cylinder positions of the base 1. A rectangular hollow area (i.e., a slotted area) with a length and width of 31mm × 31mm and a depth of 4mm is machined in the center of the upper mold 3. A 16×16 array of mounting holes (used to place the spring pillars to be installed) is machined at the bottom of this rectangular hollow area of ​​the upper mold 3. The mounting holes have a diameter of 0.4mm, a depth of 1mm, and a horizontal and vertical spacing of 1.27mm. The mounting hole array is consistent with the pad arrangement of the CBGA device to be replaced.

[0043] The pressure block 4 is 31mm long, 31mm wide, and 5.0mm high. A hollow area with a length and width of 25mm × 25mm and a depth of 3mm is machined in the middle of the pressure block 4. A 16×16 through hole array is machined at the bottom of the hollow area of ​​the pressure block 4. The diameter of the through hole is 0.4mm and the depth is 2mm. The horizontal and vertical spacing is 1.27mm. The position of the through hole corresponds to the position of the mounting hole of the upper mold 3.

[0044] like Figure 2 As shown, the specific operating steps for using the above-mentioned CBGA column planting device for column planting are as follows:

[0045] 1) Use a soldering iron to remove the solder balls from the CBGA device;

[0046] 2) Use a soldering iron and desoldering wick to remove any remaining solder from the CBGA device;

[0047] 3) Use a small stencil to print solder paste on CBGA devices, with the thickness of the stencil controlled between 0.12mm and 0.15mm;

[0048] Alternatively, a solder paste printer can be used to print solder paste on CBGA devices, and the solder paste thickness should be controlled between 0.15-0.2mm.

[0049] 4) Place the CBGA chip with solder paste printed on it onto the step in the hollow area of ​​the base 1 of the post-planting device;

[0050] 5) Install the upper mold 3 of the column planting device onto the base 1 of the column planting device via a fixed cylinder;

[0051] 6) Using pointed tweezers, place the spring pillars one by one onto the corresponding pads of the CBGA device through the mounting hole array of the upper mold 3 of the pillar placement device;

[0052] 7) Place the pressure block 4 of the column planting device into the slotted area of ​​the upper mold 3 of the column planting device;

[0053] 8) Use a reflow furnace or vapor phase furnace to perform overall furnace welding on the column planting device;

[0054] When using leaded solder paste for pillar placement, the maximum furnace temperature of the reflow oven or vapor phase furnace should be controlled at around 215±5℃. When using lead-free solder paste for pillar placement, the maximum furnace temperature of the reflow oven or vapor phase furnace should be controlled at around 245±5℃.

[0055] 9) After welding is completed, disassemble the post-planting device, remove the CBGA device, and clean the CBGA device with an equivalent alcohol-gasoline mixture to complete the post-planting process.

[0056] Using a column implantation device to implant columns into CBGA devices is a simple operation with guaranteed results. The before-and-after comparison of replacing spring columns is shown in the image. Figure 3 As shown, in order to verify the effect of the column implantation, the present invention also conducted experiments on the thermal fatigue life of CBGA devices before and after the column implantation. The CBGA device with built-in solder balls can withstand 40 cycles of thermal fatigue shock accelerated test, while the CBGA device after being replaced with spring columns can withstand more than 400 cycles of thermal fatigue shock accelerated test. It can be seen that the thermal fatigue life can be improved by more than 10 times.

[0057] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the scope of the technology disclosed in the present invention, and such modifications or substitutions should all be covered within the scope of protection of the present invention.

Claims

1. A CBGA implantation device, characterized in that: Includes the base, upper mold, and pressure block used in conjunction with it; The base has a hollow area in the middle, the size of which is larger than the CBGA device to be replaced, and the bottom of the base in the hollow area has a step for supporting and limiting the CBGA device to be replaced. The upper mold is installed on the upper part of the base, and the position on it corresponding to the hollow area is a slotted area; the thickness of the upper mold in the slotted area is less than the thickness of the upper mold body, and the upper mold in the slotted area is provided with an array of mounting holes for placing the spring pillars to be installed. The array of mounting holes is consistent with the pad arrangement of the CBGA device to be replaced. The size of the slotted area of ​​the pressure block is adapted to the size of the upper mold, and the middle part is provided with a through hole array that is consistent with the arrangement of the mounting hole array; the area on the pressure block where the through hole array is provided is a hollow area; The hollow area on the base is also provided with a heat dissipation area around it; The base and the upper mold are mounted together by fasteners, and both the base and the upper mold are provided with fixing holes for mounting the fasteners. The method for planting columns using the column planting device includes the following steps: 1) Use a soldering iron to remove the solder balls from the CBGA device; 2) Use a soldering iron and desoldering wick to remove any remaining solder from the CBGA device; 3) Use a small stencil or solder paste printer to print solder paste on CBGA devices; 4) Place the CBGA device with printed solder paste on the step in the hollow area of ​​the base of the post-planting device; 5) Install the upper mold of the column planting device onto the base of the column planting device; 6) Use tweezers to place the spring pillars one by one onto the corresponding pads of the CBGA device through the mounting hole array on the upper mold of the pillar placement device; 7) Place the pressure block of the column planting device into the slotted area of ​​the upper mold of the column planting device; 8) Use a reflow furnace or vapor phase furnace to perform overall furnace welding on the column planting device; 9) After welding is completed, disassemble the post-planting device, remove the CBGA device, and clean the CBGA device to complete the post-planting process.

2. The CBGA implantation device according to claim 1, characterized in that: The base, upper mold, and pressing block are all made of high-temperature resistant synthetic stone.

3. The column planting device according to claim 1, characterized in that: In step 3), when printing solder paste using a small stencil, the thickness of the stencil is between 0.12mm and 0.15mm. When printing using a solder paste inkjet printer, the thickness of the solder paste is between 0.15mm and 0.2mm.

4. The column planting device according to claim 1, characterized in that: Step 8): When using leaded solder paste for pillar placement, the maximum furnace temperature of the reflow oven or vapor phase furnace is controlled at 215±5℃. When using lead-free solder paste for pillar placement, the maximum furnace temperature of the reflow oven or vapor phase furnace is controlled at 245±5℃.

5. The column planting device according to claim 1, characterized in that: In step 9), the CBGA device is cleaned using a 1:1 alcohol-gasoline mixture.

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