High-reliability welding method and welding structure for LCCC packaging device and FR-4 printed board

Abstract

The invention discloses a high-reliability welding method for an LCCC packaging device and an FR-4 printed board. The high-reliability welding method comprises the following steps that S1, a ceramic adapter plate is welded to the FR-4 printed board; wherein a plurality of second bonding pads are welded on the FR-4 printed board; s2, an LCCC packaging device is welded on the ceramic adapter plate; wherein a plurality of first bonding pads are welded on the ceramic adapter plate, and the number of the first bonding pads is consistent with that of the second bonding pads; s3, using epoxy glue to reinforce four corner pins of the contact part of the ceramic adapter plate and the FR-4 printed board; and S4, respectively welding one end of a single-strand wire with the first bonding pad, and welding the other end of the single-strand wire with the second bonding pad, thereby realizing electrical interconnection between the LCCC packaging device and the FR-4 printed board. According to the invention, transfer welding is carried out through the ceramic transfer plate and the single-stranded wire, so that the thermal stress of a welding spot in a temperature alternating environment can be effectively reduced, the welding spot is prevented from cracking, and the reliability of the welding spot is effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of electronic assembly, and in particular to a high-reliability welding method and welding structure for an LCCC packaging device and an FR-4 printed circuit board. Background Art

[0002] Leadless Ceramic Chip Carrier (LCCC) packaging devices have the characteristics of small size and good electrical performance, and are widely used in aviation, aerospace, radar, military equipment and other fields.

[0003] The main material of the LCCC package device is ceramic material, and its coefficient of thermal expansion (CTE) is 6.5×10 -6 / ℃, while the CTE value of the Flame Retardant-Four (FR-4) material for printed circuit boards is 12×10 -6 / ℃, the CTE difference between these two interconnect materials is greater than 2×10 -6 / ℃, so during the service process of the two, CTE mismatch will occur, which will lead to thermal stress in the solder joint. Among them, the greater the CTE difference, the greater the thermal stress generated by the solder joint under the service conditions, and the worse the reliability of the solder joint.

[0004] To address this problem, the existing technology currently uses manual welding or adding gaskets to increase the height of the solder joints to buffer the thermal stress caused by CTE mismatch. However, after 200 identification temperature cycle tests, the results of the metallographic analysis of the slices showed that the cracking of the solder joints exceeded 50%, which did not meet the requirements of the military electronic product standards for solder joints. The solder joints have long-term reliability risks, which in turn affects the long-term reliability of the product. Therefore, designing a high-reliability welding method for LCCC packaged devices and FR-4 printed circuit boards is an urgent problem to be solved.

[0005] It should be understood that the above statements merely provide background technology related to the present invention and do not necessarily constitute prior art. Summary of the invention

[0006] The object of the present invention is to provide a high-reliability welding method and welding structure for a LCCC device and a FR-4 printed circuit board, so as to realize electrical interconnection between the LCCC device and the FR-4 printed circuit board.

[0007] In order to achieve the above-mentioned purpose, the present invention provides a high-reliability welding method for LCCC packaged components and FR-4 printed circuit boards, comprising the following steps: S1, welding a ceramic adapter board to a FR-4 printed circuit board; wherein, a plurality of second pads are welded on the FR-4 printed circuit board; S2, welding a LCCC packaged component to the ceramic adapter board; wherein, a plurality of first pads are welded on the ceramic adapter board, and the number of the first pads is consistent with the number of the second pads; S3, reinforcing the four corner points of the contact portion between the ceramic adapter board and the FR-4 printed circuit board with epoxy glue; S4, respectively welding one end of a single-strand wire to the first pad and the other end to the second pad to achieve electrical interconnection between the LCCC packaged component and the FR-4 printed circuit board.

[0008] Preferably, the S1 includes the following steps: S11, printing solder paste on the second welding pad of the FR-4 printed circuit board through a solder paste printer and a solder paste printing template; S12, programming a placement machine, and using the placement machine to mount the ceramic adapter board to the second welding pad of the FR-4 printed circuit board; S13, placing the FR-4 printed circuit board and the ceramic printed circuit board after the placement is completed into an SMT reflow furnace, and sequentially passing through the preset reflow heating zone to complete the reflow soldering.

[0009] Preferably, the S2 includes the following steps: S21, using an electric soldering iron, a tin-wicking rope and a solder wire to perform secondary tinning and gold removal on the gold-plated pins of the LCCC packaged device; S22, printing solder paste on the first welding pad of the LCCC packaged device through a solder paste printer and a solder paste printing template; S23, programming a placement machine, and using the placement machine to mount the LCCC packaged device on the first welding pad of the ceramic adapter board; S24, placing the LCCC packaged device, ceramic printed circuit board and FR-4 printed circuit board after the placement is completed into an SMT reflow oven, and sequentially passing through the preset reflow heating zone to complete the reflow soldering.

[0010] Preferably, the solder paste comprises solder and flux.

[0011] Preferably, the heating temperatures of the heating zones of the reflow oven are set to 140°C, 150°C, 160°C, 160°C, 180°C, 210°C, 250°C, 240°C, 235°C, 100°C, 60°C, 50°C, and 40°C, respectively.

[0012] Preferably, the speed range of the chain in the reflow furnace is 60 cm / min to 100 cm / min.

[0013] Preferably, the total length of the reflow furnace is 6 m, and the lengths of the heating zones in the reflow furnace are equal.

[0014] Preferably, in S3, a needle is used to dip epoxy glue, and the four corners of the ceramic adapter plate are dotted with glue. After the dosing, the entire welded structure is placed in an oven for drying to solidify the epoxy glue.

[0015] Preferably, the oven drying temperature is 125° C. and the drying time is 15 min.

[0016] The present invention also provides a high-reliability welding structure, which is implemented by the high-reliability welding method of the LCCC packaged device and the FR-4 printed circuit board described above, including: an FR-4 printed circuit board, on which a second welding pad is arranged; a ceramic adapter board, which is welded on the FR-4 printed circuit board through the second welding pad, and on which a first welding pad is arranged; an LCCC packaged device, which is welded on the ceramic adapter board 2 through the first welding pad; wherein the FR-4 printed circuit board is larger than the ceramic adapter board, and the ceramic adapter board is larger than the LCCC packaged device; a plurality of first pads, which are arranged on a portion of the ceramic adapter board that is not covered by the LCCC packaged device; a plurality of second pads, which are arranged on a portion of the FR-4 printed circuit board that is not covered by the ceramic adapter board; and a plurality of single-strand wires, wherein each of the first pads is welded to a second pad through a single-strand wire.

[0017] In summary, compared with the prior art, the high-reliability welding method for LCCC devices and FR-4 printed circuit boards provided by the present invention can effectively reduce the thermal stress on the solder joints in a temperature alternating environment, avoid solder joint cracking, and effectively improve the reliability of the solder joints, thereby improving the life and reliability of the product obtained after the soldering is completed. The high-reliability welding structure provided by the present invention has a higher long-term reliability of the solder joints, is not easily affected by thermal stress, and significantly improves the product quality, which has great practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of a high-reliability welding structure in the present invention;

[0019] Figure 2 The flowchart of the high-reliability welding method of the LCCC packaged device and the FR-4 printed circuit board in the present invention;

[0020] Figure 3 This is a flow chart for verifying the reliability test of solder joints in the present invention;

[0021] Figure 4 A metallographic microscope image of a solder joint after a reliability test using the soldering method of the present invention;

[0022] Figure 5This is a metallographic microscope image of a solder joint after a reliability test using a conventional soldering method. DETAILED DESCRIPTION

[0023] The following is combined with Figures 1 to 5 , the present invention is further explained by describing a preferred specific embodiment in detail.

[0024] It should be noted that the drawings are in a very simplified form and use non-precise proportions. They are only used to conveniently and clearly assist in explaining the embodiments of the present invention, and are not used to limit the conditions for the implementation of the present invention. Therefore, they have no substantive technical significance. Any structural modification, change in proportional relationship or adjustment of size, without affecting the effects and purposes that can be achieved by the present invention, should still fall within the scope of the technical content disclosed by the present invention.

[0025] It should be noted that, in the present invention, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only the elements explicitly listed, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0026] like Figure 1 As shown, the present invention provides a high-reliability welding structure, comprising: an LCCC packaging device 1, a ceramic adapter board 2, a plurality of first pads 3, a plurality of single-strand wires 4, a plurality of second pads 5 and a FR-4 printed board 6; wherein the FR-4 printed board 6 is provided with a second welding pad (not shown in the figure), and the ceramic adapter board 2 is welded on the FR-4 printed board 6 through the second welding pad, wherein the FR-4 printed board 6 is larger than the ceramic adapter board 2; the ceramic adapter board 2 is provided with a first welding pad (not shown in the figure), and the L The CCC packaged device 1 is welded on the ceramic adapter board 2 via a first welding pad, wherein the ceramic adapter board 2 is larger than the LCCC packaged device 1; a plurality of first welding pads 3 are welded on a portion of the ceramic adapter board 2 not covered by the LCCC packaged device 1, and a plurality of second welding pads 5 are welded on a portion of the FR-4 printed circuit board 6 not covered by the ceramic adapter board 2; the number of the first welding pads 3 is the same as the number of the second welding pads 5, and each of the first welding pads 3 is welded to a second welding pad 5 via a single-strand wire 4.

[0027] like Figure 2As shown, the present invention also provides a high-reliability welding method for an LCCC packaged device and a FR-4 printed circuit board, so as to form a high-reliability welding structure of the above-mentioned LCCC packaged device 1 and the FR-4 printed circuit board 6 by welding, which specifically comprises the following steps:

[0028] S1, welding the ceramic adapter board 2 to the FR-4 printed board 6; wherein the FR-4 printed board 6 is welded with a plurality of second pads 5;

[0029] S2, welding the LCCC packaged device 1 to the ceramic adapter plate 2; wherein a plurality of first pads 3 are welded on the ceramic adapter plate 2, and the number of the first pads 3 is consistent with the number of the second pads 5;

[0030] S3, using epoxy glue to reinforce the four corners of the contact portion between the ceramic adapter board 2 and the FR-4 printed circuit board 6;

[0031] S4. Weld one end of the single-strand wire 4 to the first pad 3, and the other end to the second pad 5, until all the first pads 3 and the second pads 5 are welded, thereby realizing electrical interconnection between the LCCC packaged device 1 and the FR-4 printed circuit board 6.

[0032] Furthermore, the S1 specifically includes the following steps:

[0033] S11, printing solder paste on the second solder pad of the FR-4 printed circuit board 6 by using a solder paste printer and a solder paste printing template;

[0034] S12, programming a chip mounter, and using the chip mounter to mount the ceramic adapter board 2 onto the second welding pad of the FR-4 printed circuit board 6;

[0035] S13, placing the FR-4 printed circuit board 6 and the ceramic printed circuit board 2 after the patch is completed into a surface mounting technology (Surface Mounted Technology, SMT) reflow oven, and through the chain in the reflow oven, the FR-4 printed circuit board 6 and the ceramic printed circuit board 2 after the patch are completed flow through the preset reflow heating zone in sequence to complete the reflow soldering.

[0036] Furthermore, the S2 specifically includes the following steps:

[0037] S21, using an electric soldering iron, a tin-absorbing rope and a solder wire to perform secondary tinning and gold removal on the gold-plated pins of the LCCC package device 1;

[0038] S22, printing solder paste on the first solder pad of the LCCC packaged device 1 by using a solder paste printer and a solder paste printing template;

[0039] S23, programming a chip mounter, and using the chip mounter to mount the LCCC packaged device 1 onto the first welding pad of the ceramic adapter board 2;

[0040] S24, placing the LCCC packaged device 1, ceramic printed circuit board 2 and FR-4 printed circuit board 6 after the patch is completed into the SMT reflow oven, and through the chain in the reflow oven, the LCCC packaged device 1, ceramic printed circuit board 2 and FR-4 printed circuit board 6 after the patch are completed flow through the preset reflow heating zone in sequence to complete the reflow soldering.

[0041] Furthermore, in S11 and S22, the solder paste includes solder and flux. In a preferred embodiment of the present invention, the solder paste is preferably Sn63Pb37, and its melting point is 183°C; the solder paste printing template needs to be opened according to the shapes and sizes of the second welding pad and the second welding pad respectively, and in a preferred embodiment of the present invention, the thickness of the printing template is preferably 0.13 mm.

[0042] Furthermore, in S13 and S24, the heating temperatures of the preset heating zones of the SMT reflow oven are set to 140°C, 150°C, 160°C, 160°C, 180°C, 210°C, 250°C, 240°C, 235°C, 100°C, 60°C, 50°C, and 40°C, respectively, wherein the total length of the reflow oven is 6m, and the lengths of the heating zones in the reflow oven are equal; and the speed range of the chain in the reflow oven is 60cm / min to 100cm / min, preferably 80cm / min, to complete the final welding.

[0043] Furthermore, in the S3, the epoxy glue must first be taken out of the refrigerated state and then warmed up at room temperature. After warming up for a certain period of time, the epoxy glue is dipped with a needle and dotted on the four corners of the ceramic adapter plate 2. After dosing, the overall welded structure is placed in an oven for drying to solidify the epoxy glue to complete the reinforcement operation; wherein the warming up time is preferably 30 minutes, the oven drying temperature is preferably 125°C, and the oven drying time is preferably 15 minutes.

[0044] Preferably, in a preferred embodiment of the present invention, the LCCC package device 1 is a LCCC44 package device having a size of 16.5 mm×16.5 mm; the ceramic adapter board 2 is a RA300B ceramic adapter board; and the epoxy glue is E2605B epoxy glue.

[0045] It is understandable that after the LCCC package device 1 and the FR-4 printed circuit board 6 are welded, a solder joint reliability test needs to be performed to verify the effect after welding. Figure 3As shown, the method for experimental verification of solder joint reliability specifically includes the following steps: first, perform an appearance inspection on the completed sample, and after the inspection is correct, perform a temperature cycle test with a temperature range of -50°C to 100°C for more than 200 times, and perform an appearance inspection again. After the second appearance inspection is correct, perform a metallographic section analysis on the sample solder joint under a microscope. If the sample solder joint has no cracks at this time, it proves that the welding is highly reliable. If the sample solder joint has cracks at this time, it proves that the welding is unreliable.

[0046] like Figure 4 and Figure 5 As shown, there are metallographic microscope pictures of solder joints after reliability test using the soldering method of the present invention and metallographic microscope pictures of solder joints after reliability test using the soldering method of the prior art, respectively. It can be seen that no cracks appeared in the solder joints after reliability test using the soldering method of the present invention, while cracks appeared in the solder joints after reliability test using the soldering method of the prior art.

[0047] In summary, the high-reliability welding method of a LCCC packaged device and a FR-4 printed circuit board provided by the present invention can effectively reduce the thermal stress of the solder joint in a temperature alternating environment by using a ceramic adapter plate and a single-strand wire for transfer welding, effectively improve the reliability of the solder joint, and further improve the life and reliability of the product obtained after the welding is completed. The high-reliability welding structure provided by the present invention has a reliable solder joint, is not easily affected by thermal stress, has extremely strong reliability, and has great practical value.

[0048] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A high-reliability welding method for LCCC packaged devices and FR-4 printed circuit boards, characterized in that: The following steps are involved: S1, welding the ceramic adapter board to the FR-4 printed board; wherein the FR-4 printed board is welded with a plurality of second pads; S2, welding the LCCC packaged device to the ceramic adapter plate; wherein a plurality of first pads are welded on the ceramic adapter plate, and the number of the first pads is consistent with the number of the second pads; S3, using epoxy glue to reinforce the four corners of the contact part between the ceramic adapter board and the FR-4 printed circuit board; S4. Solder one end of the single-strand wire to the first soldering pad and the other end to the second soldering pad respectively to achieve electrical interconnection between the LCCC packaged device and the FR-4 printed circuit board.

2. The high-reliability welding method of the LCCC packaged device and the FR-4 printed circuit board according to claim 1, characterized in that: The S1 includes the following steps: S11, printing solder paste on the second welding pad of the FR-4 printed circuit board by using a solder paste printer and a solder paste printing template; S12, programming a chip mounter, and using the chip mounter to mount the ceramic adapter board onto the second welding pad of the FR-4 printed circuit board; S13, put the FR-4 printed circuit board and ceramic printed circuit board after the patch is completed into the SMT reflow oven, and flow through the preset reflow soldering heating zone in turn to complete the reflow soldering.

3. The high-reliability welding method of the LCCC packaged device and the FR-4 printed circuit board according to claim 1, characterized in that: The S2 comprises the following steps: S21, use electric soldering iron, tin-absorbing rope and solder wire to perform secondary tinning and gold removal on the gold-plated pins of LCCC package components; S22, printing solder paste on the first welding pad of the LCCC packaged component by using a solder paste printer and a solder paste printing template; S23, programming a chip mounter, and using the chip mounter to mount the LCCC packaged device onto the first welding pad of the ceramic adapter board; S24, put the LCCC packaged components, ceramic printed circuit boards and FR-4 printed circuit boards after the patch is completed into the SMT reflow oven, and flow through the preset reflow heating zone in turn to complete the reflow soldering.

4. The high-reliability welding method of the LCCC packaged device and the FR-4 printed circuit board as claimed in claim 2 or 3, characterized in that: The solder paste includes solder and flux.

5. The high-reliability welding method of the LCCC packaged device and the FR-4 printed circuit board as claimed in claim 2 or 3, characterized in that: The heating temperatures of the heating zones of the reflow oven are set to 140°C, 150°C, 160°C, 160°C, 180°C, 210°C, 250°C, 240°C, 235°C, 100°C, 60°C, 50°C, and 40°C, respectively.

6. The high-reliability welding method of the LCCC packaged device and the FR-4 printed circuit board as claimed in claim 5, characterized in that: The speed range of the chain in the reflow furnace is 60 cm / min to 100 cm / min.

7. The high-reliability welding method of the LCCC packaged device and the FR-4 printed circuit board as claimed in claim 6, characterized in that: The total length of the reflow furnace is 6 m, and the lengths of the heating zones in the reflow furnace are equal.

8. The high-reliability welding method of the LCCC packaged device and the FR-4 printed circuit board according to claim 1, characterized in that: In the above-mentioned S3, epoxy glue is dipped into a needle and glue is applied to the four corners of the ceramic adapter plate. After the glue is applied, the whole welding structure is placed in an oven for drying to solidify the epoxy glue.

9. The high-reliability welding method of the LCCC packaged device and the FR-4 printed circuit board as claimed in claim 8, characterized in that: The oven drying temperature is 125° C. and the drying time is 15 min.

10. A high-reliability welding structure, implemented by the high-reliability welding method of the LCCC packaged device and the FR-4 printed circuit board as claimed in any one of claims 1 to 9, characterized in that: include: An FR-4 printed circuit board having a second solder pad disposed thereon; A ceramic adapter board is welded on the FR-4 printed circuit board via a second welding pad and is provided with a first welding pad; The LCCC packaged device is welded on the ceramic adapter plate 2 via a first welding pad; Wherein, the FR-4 printed circuit board is larger than the ceramic adapter board, and the ceramic adapter board is larger than the LCCC packaged device; A plurality of first pads, arranged on a portion of the ceramic adapter board not covered by the LCCC package device; A plurality of second pads are arranged on a portion of the FR-4 printed circuit board that is not covered by the ceramic adapter board; A plurality of single-strand wires, each of the first welding pads is connected to a second welding pad by welding through one of the single-strand wires.

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