Installation method for QFP packaging device of spacecraft electronic product

Abstract

The invention relates to an installation method for a QFP packaging device of a spacecraft electronic product, and belongs to the technical field of electronic installation processes. The method comprises the steps of designing an electric fitting auxiliary part of a CQFP, pasting the electric fitting auxiliary part, welding the device, and gluing and reinforcing the electric fitting auxiliary part. The invention provides a process capable of realizing first flow welding and then reinforcement of the CQFP device, by designing a proper electric fitting auxiliary part and cooperating with a specific process flow and a bonding reinforcement method, reliability reinforcement is performed after automatic welding of the CQFP device is completed, interpenetration of procedures of welding and dispensing reinforcement of the CQFP device in a connection process is avoided, the reliability of the CQFP device is improved, and the production efficiency of the CQFP device is improved. The production efficiency is improved, and meanwhile, the consistency and reliability of welding and reinforcing are improved.

Description

Technical Field

[0001] The present invention relates to a mounting method for a ceramic package QFP (hereinafter referred to as CQFP) device of aerospace electronic products. The method includes the design of an electrical installation auxiliary for the CQFP device, the pasting of the electrical installation auxiliary, the soldering of the device, and the adhesive reinforcement process method, belonging to the technical field of electronic assembly technology. Background Art

[0002] With the continuous progress of electronic technology, semiconductor packaging technology has developed greatly. In particular, the requirements for high performance and miniaturization of high-reliability products have further promoted the development of high-density and high-integration IC chip packaging technology, making large-scale integrated circuits widely used in electronic systems. Although leadless packaging has developed rapidly in the IC packaging industry, such as BGA and QFN, leaded chip products, especially SMDs, still play an important role in the IC market, including FP and CQFP devices. Due to its many advantages such as high density, high reliability, and excellent electrical performance, CQFP devices are widely used in large-scale integrated circuits. However, due to the relatively large size and high weight of the device body and the relatively small pin solder joints, the anti-vibration ability is weak after being assembled on the printed circuit board. Therefore, the reinforcement of the device is very important for the entire assembly process.

[0003] Many users in the military field still use manual methods for soldering CQFP devices. Before manual soldering of the device, epoxy glue is dot-sealed at the bottom of the body, and then the device is positioned and soldered to the printed circuit board pads. This method can better reinforce the device, but the production efficiency is low, restricting the improvement of production capacity. A small number of users perform automatic soldering of CQFP devices by reflow soldering. However, after soldering, only the four corners of the device can be reinforced by epoxy glue / silicone rubber end-sealing and the polyurethane glue with strong fluidity at the bottom of the device can be used for sticking and fixing. Compared with the bottom epoxy glue filling, the reinforcement method has relatively weak mechanical properties and is difficult to meet the use of products under the harsh mechanical conditions with a total root mean square of random vibration above 20g. For a certain product device, the four-corner epoxy glue end-sealing method + bottom filling of polyurethane glue for reinforcement was used. In a high-mechanical environment, cracks occurred in multiple pins of the device solder joints, resulting in signal abnormalities. Eventually, the device was repaired by manual soldering and bottom filling with epoxy glue for reinforcement, and no problems were found after verification. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: overcoming the deficiencies of the prior art, and in order to achieve high-efficiency automatic soldering and reliable reinforcement of CQFP devices, a mounting structure and method for CQFP devices of aerospace electronic products are proposed.

[0005] The technical solution of the present invention is:

[0006] An installation structure for CQFP devices of aerospace electronic products, comprising a substrate with PCB pads on its surface; an electrical installation auxiliary, connected to the surface of the PCB substrate, and the inner sides of the four rows of pads of the PCB pads are the inner sides of the PCB pads; a device, located on the side of the electrical installation auxiliary away from the substrate, the pins connected to the device are located on the PCB pads, and there is reinforcing glue between the device and the PCB substrate and at the cross-hollowed position of the electrical installation auxiliary.

[0007] The electrical installation auxiliary includes a cross-frame part and a peripherally hollowed part with rounded corners, and the four rounded-corner positions face the inner corners of the four corners of the PCB pads.

[0008] An installation method for CQFP devices of aerospace electronic products, comprising

[0009] Design and produce the corresponding electrical installation auxiliary for the device;

[0010] Complete solder paste printing on the PCB pads;

[0011] Paste the electrical installation auxiliary on the side of the PCB pads printed with solder paste;

[0012] Mount the device onto the PCB pads and at the central position inside the PCB pads. The device is located on the side of the electrical installation auxiliary away from the PCB substrate, the pins connected to the device are above the PCB pads, the rounded-corner positions of the inner corners of the cross-hollowed part of the electrical installation auxiliary face the inner corners of the four corners of the PCB pads. The electrical installation auxiliary is reflow soldered together with the PCB substrate and the device, and the epoxy glue at the bottom of the electrical installation auxiliary is cured during the high-temperature process of reflow soldering to obtain a PCBA assembly;

[0013] Bottom adhesive reinforcement: Inject and cure reinforcing glue at the bottom of the device of the PCBA assembly and at the four-corner hollowed positions of the electrical installation auxiliary.

[0014] Design and produce a suitable electrical installation auxiliary for different devices.

[0015] Specifically, the height difference between the height of the electrical installation auxiliary and the height from the bottom of the device body to the bottom of the pins is 0 mm to 0.25 mm. Ensure that there is a gap between the upper end of the electrical installation auxiliary and the bottom of the device, the electrical installation auxiliary will not lift the device, and when bottom adhesive reinforcement is carried out, the reinforcing glue can flow along the hollowed part of the auxiliary to the bottom of the device, and the reinforcing glue will not overflow from the gap between the upper end of the electrical installation auxiliary and the bottom of the device.

[0016] The electrical installation auxiliary is of a cross structure, the edge distance is the inner pad spacing minus 4 mm to 6 mm, the four corners are hollowed squares, the side length of the hollowed square is 8 mm to 10 mm, there are rounded corners at the inner corner positions, the radius of the rounded corner is 1 / 2 of the side length of the square, and the hollowed area should ensure to be 3.5%-6% of the bottom area of the CQFP device body.

[0017] The electrical installation auxiliary is pasted on the PCB substrate with epoxy glue.

[0018] When using epoxy glue to paste the electrical installation auxiliary, apply the epoxy glue to the middle position of the electrical installation auxiliary, and then paste the electrical installation auxiliary to the four corners inside the PCB pads. The four corners are rounded towards the four corners inside the PCB pads.

[0019] After the device is mounted, the pin offset is less than 5% of the width of the PCB pad.

[0020] The material of the electrical installation auxiliary is the same as that of the substrate, which is epoxy glass cloth.

[0021] The reinforcing glue used for the bottom adhesive reinforcement is epoxy glue.

[0022] The bottom adhesive reinforcement method includes: using a glue injection tool to inject epoxy glue to the bottom of the device until the hollow part of the cross-shaped electrical installation auxiliary is filled with the glue, stop dispensing glue, and cure the glue.

[0023] Specifically, pour the prepared epoxy glue into a 6 ml syringe. Install a glue injection hose at the head of the syringe and connect the tail to a dispenser. Insert the dispensing head into the bottom of the device along the gaps at the four corners of the CQFP device. Start the dispenser until the glue fills the hollow part of the cross-shaped auxiliary, stop dispensing glue, and use the same method to inject and reinforce the epoxy glue at the other three positions of the device.

[0024] The curing temperature and method of the epoxy glue are determined according to the type of epoxy glue selected.

[0025] The electrical installation auxiliary is fixed to the PCB substrate with epoxy glue. The epoxy glue component between the electrical installation auxiliary and the PCB substrate is the same as the material of the reinforcing glue used for the bottom adhesive reinforcement.

[0026] In summary, the present application at least includes the following beneficial technical effects:

[0027] The present invention proposes a process that can realize the reflow soldering of CQFP devices first and then reinforcement. By designing a suitable electrical installation auxiliary, cooperating with a specific process flow and bonding reinforcement method, the reliability reinforcement is carried out after the automatic soldering of CQFP devices is completed, avoiding the interspersed processes of soldering and dispensing reinforcement during the assembly of CQFP devices, improving the production efficiency, and at the same time improving the consistency and reliability of soldering and reinforcement.

[0028] The invention proposes an installation method for CQFP devices of aerospace electronic products. By designing suitable electrical auxiliary parts for different CQFP devices and presetting them before electrical installation of the devices, high-reliability reinforcement of the CQFP devices after automatic welding can be achieved, the interlacing of welding and adhesive reinforcement processes during the assembly of the CQFP devices can be reduced, the assembly efficiency of the devices can be improved, and the consistency and reliability of welding and reinforcement can be improved at the same time. The method can be reliably used under severe mechanical conditions with a total root mean square of random vibration of more than 20g. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of the installation structure of the CQFP device in the embodiment of the present application;

[0030] Figure 2 It is a schematic diagram of the structure of the electrical auxiliary components in the embodiment of the present application;

[0031] Figure 3 It is a schematic diagram of the structure after the electrical auxiliary components in the embodiment of the present application are bonded to the PCB substrate.

[0032] Description of reference numerals:

[0033] 6. Substrate; 61. PCB pad; 62. Inside of PCB pad

[0034] 7. Electrical auxiliary parts; 71. Cross part; 72. Cross hollowing glue point; 73. Rounding position

[0035] 8. Device; 81. Pin; DETAILED DESCRIPTION

[0036] The present application is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0037] In this embodiment, the device is a CQFP256 device.

[0038] The present application embodiment discloses a mounting structure and method for a CQFP256 device 8 for aerospace electronic products, referring to Figure 1 and Figure 2 The installation structure includes a PCB substrate 6 with a PCB pad 61 on the surface, an electrical auxiliary component 7 connected to the surface of the PCB substrate 6, and a device 8. The device 8 is located on the side of the electrical auxiliary component 7 away from the substrate 6. The pin 81 connected to the device 8 is located on the printed circuit board pad 61. The electrical auxiliary component 7 is located at the center of the inner side 62 of the PCB pad, and the rounded position 73 faces the four corners of the inner side 62 of the PCB pad. Reinforcement glue is provided between the bottom of the device 8 and the PCB substrate 6 and at the cross-hollowed glue point position 72 of the electrical auxiliary component. The inner side of the four rows of pads of the PCB pad 61 is the inner side 62 of the PCB pad.

[0039] The electrical installation auxiliary part 7 includes a cross part 71, a cross-shaped hollow dispensing position 72 for removing material at the four corners, and a rounded position 73 with rounded corners at the four corners.

[0040] The installation method includes the following steps:

[0041] (1) Design and produce a suitable electrical installation auxiliary part 7 for different CQFP devices 8.

[0042] Design principle of the electrical installation auxiliary part 7: The material of the electrical installation auxiliary part 7 is the same as that of the PCB substrate, which is epoxy glass cloth; the height difference between the electrical installation auxiliary part 7 and the height from the bottom of the device 8 body to the bottom of the pins 81 is controlled within 0 mm to 0.25 mm to ensure there is a gap between the upper end of the electrical installation auxiliary part 7 and the bottom of the device 8; the electrical installation auxiliary part 7 is in a cross shape, and the distance between the two sides is the inner pad spacing minus 4 mm to 6 mm; the side length of the square of the cross-shaped hollow dispensing position of the electrical installation auxiliary part is 8 mm to 10 mm, and there are rounded corners at the inner corner positions, and the radius of the rounded corner is 1 / 2 of the side length of the square, and the hollowed area should ensure to be 3.5% - 6% of the bottom area of the CQFP device body.

[0043] (2) Use a screen printing machine to complete solder paste printing on the PCB pads 61, and then paste the electrical installation auxiliary part 7 in step (1) at the exact center position of the inner side of the PCB pads 62 with epoxy glue, and the rounded position 73 faces the four corners of the inner side of the PCB pads 62.

[0044] The adhesive used is epoxy glue, and its ratio, preparation method, and the usage time limit after mixing are determined according to the type of glue selected.

[0045] When using epoxy glue to paste the electrical installation auxiliary part 7, apply an appropriate amount of epoxy glue to the middle position of the electrical installation auxiliary part, and then paste the electrical installation auxiliary part to the center position of the inner side of the PCB pads. The rounded position faces the four corners of the inner side of the PCB pads. After pasting, gently press the electrical installation auxiliary part 7 to ensure that the electrical installation auxiliary part 7 and the substrate 6 are in a fitting state.

[0046] (3) Use equipment such as a pick-and-place machine or a rework station to mount the CQFP device 8. After the device 8 is mounted, the offset of the pins 81 is less than 5% of the pad width. The electrical installation auxiliary part 7 is reflow soldered together with the device 8, and the CQFP device 8 and the PCB substrate 6 are soldered together. At the same time, the epoxy glue at the bottom of the electrical installation auxiliary part 7 is cured during the high-temperature process of reflow soldering to obtain a PCBA.

[0047] (4) Perform bottom glue reinforcement on the CQFP device 8 on the PCBA.

[0048] The glue used for bottom glue reinforcement is epoxy glue, and its ratio, preparation method, and the usage time limit after mixing are determined according to the type of glue selected.

[0049] The reinforcement method is as follows: Pour the prepared epoxy adhesive into a 6-ml syringe. Install a glue injection hose at the head of the syringe and connect the tail to a dispensing machine. Insert the dispensing head along the four corners of the CQFP device 8 into the bottom of the device 8. After touching the rounded position 73 of the electrical installation auxiliary part, slightly withdraw it. Start the dispensing machine until the glue overflows (the glue fills the space between the bottom of the device 8 and the substrate 6 and reaches the edge position of the device 8, then stop dispensing). Use the same method to inject and reinforce the epoxy glue at the other three positions of the device 8 to complete the bottom bonding and reinforcement of the device 8.

[0050] The curing temperature and method of the epoxy glue are determined according to the type of epoxy glue selected.

[0051] Conduct environmental tests on the finally obtained PCBA board assembly in accordance with ECSS-Q-ST-70-08C. After passing the test assessment, the solder joint metallography shows no cracks, and the test results indicate that it meets the standard qualification criteria.

[0052] Example 1

[0053] An installation method for a CQFP device 8 of aerospace electronic products. The CQFP device 8 is in a CQFP256 package. The length and width of the device 8 body (excluding pins) are 36 mm, and the length and width including pins are 41.4 mm. The distance from the bottom of the device 8 body to the bottom of the pins 81 is 0.6 mm. The inner size of the device 8 solder pad is 37.2 mm × 37.2 mm. The steps of this method include:

[0054] (1) Design and produce an electrical installation auxiliary part 7 for the CQFP256 device 8. The material of the electrical installation auxiliary part 7 is epoxy glass cloth; the electrical installation auxiliary part 7 is cross-shaped; the height of the electrical installation auxiliary part 7 is 0.4 mm, and the height difference from the device 8 body to the bottom of the device 8 pins 81 is 0.2 mm; the overall two-side distance of the electrical installation auxiliary part 7 is 32.2 mm, the side length of the square hollowed out at the four corners is 8 mm, the inner corner rounding radius is 4 mm, and its area is 4.7% of the bottom area of the CQFP256 device body.

[0055] (2) Use a screen printing machine to complete solder paste printing on the PCB solder pad 61, and then paste the electrical installation auxiliary part 7 in step (1) at the central area of the solder pad of the CQFP256 device 8 using epoxy glue.

[0056] When pasting the electrical installation auxiliary part 7, just apply an appropriate amount of epoxy glue to the middle position of the cross part 71 of the electrical installation auxiliary part 7, and then paste the electrical installation auxiliary part 7 to the central position of the inner side 62 of the PCB solder pad. The rounded position 73 of the electrical installation auxiliary part faces the four corners of the inner side 62 of the PCB solder pad. After pasting ( Figure 3 ), gently press the electrical installation auxiliary part 7 to ensure that the electrical installation auxiliary part 7 and the substrate 6 are in a fitting state.

[0057] The epoxy adhesive used for bonding is an epoxy glue, and the ratio, preparation method, and the usage time limit after mixing the glue are determined according to the type of glue selected.

[0058] (3) Use a pick-and-place machine to mount the CQFP256 device 8. After the device 8 is mounted, the offset of the pins 81 is less than 5% of the pad width; the electrical assembly auxiliary 7 is reflow soldered together with the device 8, and the epoxy glue at the bottom of the electrical assembly auxiliary 7 is cured during the high-temperature process to obtain the PCBA.

[0059] (4) After welding is completed, inject epoxy glue at the four corner positions at the bottom of the CQFP256 device 8. Insert the dispensing head into the bottom of the device 8 along the gaps at the four corners of the QFP device, slightly withdraw after touching the rounded position 73 of the electrical assembly auxiliary, start the dispenser, until the glue overflows, stop dispensing, and use the same method to inject and reinforce epoxy glue at the other three positions of the device 8 to complete the bottom bonding and reinforcement of the device 8. The curing temperature and method of the epoxy glue are determined according to the type of epoxy glue selected.

[0060] The ratio and effective usage time of the epoxy glue are determined according to the glue selected. The general preparation method is: stir and mix epoxy resin, curing agent, and filler (optional) in a "figure 8" shape to obtain the epoxy glue.

[0061] The epoxy glue is filled into a 6 ml syringe in the form of a small wooden stick, a dispensing hose is installed at the head of the syringe, and the tail is connected to the dispenser.

[0062] Finally, the obtained PCBA board assembly is subjected to environmental tests in accordance with ECSS-Q-ST-70-08C. After passing the test assessment, no cracks are found in the solder joint metallography. The test results show that the standard pass criteria are met.

[0063] The implementation principle of this application is as follows: By designing a suitable electrical assembly auxiliary 7 for different CQFP devices 8 and pre-setting it before the electrical assembly of the device 8, the present invention can achieve high-reliability reinforcement of the CQFP device 8 after automatic soldering, reduce the process interspersion of welding and adhesive reinforcement during the assembly of the CQFP device 8, improve the production efficiency of the device 8 from manual soldering to automatic soldering, and at the same time improve the consistency and reliability of welding and reinforcement. This installation method can meet the more stringent usage environment requirements of the product and ensure the reliability of the product.

[0064] Although the present invention is disclosed above with preferred embodiments, it is not used to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined by the claims of the present invention.

[0065] The parts not detailed in the present invention belong to the common general knowledge of those skilled in the art.

Claims

1. An installation structure for CQFP devices of aerospace electronic products, characterized in that: It includes a PCB substrate, on which four rows of PCB pads are arranged, the four rows of PCB pads are located at four sides of the same quadrilateral, an electrical auxiliary part is connected to the surface of the PCB substrate and is located at the central position of the inner side of the PCB pad; the electrical auxiliary part is a cross structure, a CQFP device is located at a side of the electrical auxiliary part away from the substrate, the pins connected to the CQFP device are located on the PCB pad, and reinforcing glue is provided between the CQFP device and the PCB substrate and in the hollow part between the CQFP device and the electrical auxiliary part.

2. The installation structure according to claim 1, characterized in that: The electrical auxiliary component is a cross structure, the four corners of which are hollowed-out squares, and chamfers are provided at the inner corners, with the chamfers facing the four inner corners of the PCB pad.

3. The installation structure according to claim 2, characterized in that: The cross structure margin is the inner side spacing of the pad minus 4mm to 6mm.

4. The installation structure according to claim 2, wherein: The side length of the hollowed-out square is 8mm-10mm, and a rounding is provided at the inner corner, and the rounding radius is 1 / 2 of the side length of the square. The hollowed-out area should be guaranteed to be 3.5%-6% of the bottom area of ​​the CQFP device body.

5. A mounting method for a CQFP device of aerospace electronic products according to any one of claims 1-4, characterized in that: include Complete solder paste printing on PCB pads; Paste the electrical auxiliary parts in the center of the inner side of the PCB pad; Mount the device on the PCB pad. The device is located on the side of the electrical auxiliary part away from the PCB substrate. The pins connected to the device are located above the PCB pad. The squares at the hollowed-out positions of the electrical auxiliary part are rounded toward the four corners inside the PCB pad. The electrical auxiliary part is reflow soldered together with the PCB substrate and the device to obtain a PCBA assembly. Inject reinforcing glue between the bottom of the PCBA component and the PCB substrate, and between the hollowed-out parts of the electrical auxiliary parts and cure.

6. The installation method according to claim 5, wherein: The electrical auxiliary component is attached to the PCB substrate by epoxy glue; after the device is mounted, the pin offset is less than 5% of the PCB pad width, and the height difference between the electrical auxiliary component and the height from the bottom of the device body to the bottom of the pin is 0mm to 0.25mm.

7. The installation method according to claim 5, characterized in that: The bottom adhesive reinforcement uses epoxy glue.

8. The installation method according to claim 5, characterized in that: The bottom adhesive reinforcement method includes: using a glue injection tool to inject epoxy glue into the bottom of the device through the four corners of the CQFP in sequence until the glue fills the hollowed-out part of the electrical auxiliary parts, stopping the glue dispensing, and curing the glue.

9. The installation method according to claim 5, characterized in that: The electrical auxiliary component is fixed to the PCB substrate by epoxy glue.

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