A contact chip soldering process

Abstract

This application discloses a contact-type chip soldering process, relating to the field of chip soldering technology. The process includes the following steps: printing solder paste dots at the contacts within the soldering area of ​​a circuit board; heating the solder paste dots to melt them; cooling the molten solder paste dots on the circuit board to form solder dots at the contacts; printing a solder paste layer at the contacts within the solder paste layer; attaching a chip to the soldering area of ​​the circuit board, such that the chip's contacts are in contact with the solder paste layer; heating the solder paste layer and solder dots to melt them; cooling the soldering area of ​​the circuit board to solidify the molten solder paste layer and solder dots, forming solder joints, and soldering the chip onto the circuit board. This application effectively reduces air bubbles generated within the solder joints and improves the quality of the solder joints.

Description

Technical Field

[0001] This application relates to the field of chip bonding technology, and in particular to a contact-type chip bonding process. Background Technology

[0002] Contact-type chips, also known as LGA chips, are characterized by replacing the traditional pin-type packaging with metal contact packaging, resulting in smaller chip size, lower contact resistance, and improved electrical performance.

[0003] In related technologies, soldering a contact-type chip onto a circuit board first requires printing solder paste into the corresponding contacts on the circuit board. Then, the chip is attached to the circuit board, and the chip and circuit board are sent together into a reflow soldering machine. The reflow soldering machine heats the chip, circuit board, and solder paste. At this time, the solder paste between the chip and the circuit board will melt. Finally, the chip and circuit board are cooled, and the molten solder paste is cooled, thus completing the chip soldering operation.

[0004] Regarding the aforementioned technologies, solder paste contains a significant amount of flux to improve soldering performance. However, flux is typically a mixture with rosin as its main component. During soldering, some of the flux evaporates, generating corresponding gases. This can easily lead to numerous air bubbles within the solder joint, resulting in lower solder joint quality and indicating areas for improvement. Summary of the Invention

[0005] In order to improve the problem that when soldering contact-type chips, the gas generated by flux evaporation easily leads to a large number of bubbles in the solder joint, resulting in low solder joint quality, this application provides a contact-type chip soldering process.

[0006] This application provides a contact-type chip welding process, which adopts the following technical solution:

[0007] A contact-type chip bonding process includes the following steps:

[0008] Solder paste dots are printed at the contacts within the soldering area of ​​the circuit board;

[0009] The solder paste points are heated until they melt.

[0010] The molten solder paste on the circuit board is cooled, and solder points are formed at the contacts;

[0011] Print solder paste at the contacts in the soldering area of ​​the circuit board, ensuring that the solder points are located within the solder paste layer;

[0012] The chip is attached to the soldering area of ​​the circuit board so that the chip's contacts are in contact with the solder paste layer.

[0013] The solder paste layer and solder joints are heated to melt them;

[0014] The soldering area of ​​the circuit board is cooled, causing the molten solder paste layer and solder points to solidify and form solder joints, and the chip is soldered onto the circuit board.

[0015] By adopting the above technical solution, when the solder paste melts, the gas generated by the flux within the solder paste can be directly discharged. When the chip is attached to the circuit board, the solder paste is in a solid state, and the support of the solder paste provides a large gap between the chip and the circuit board. When the solder paste layer and solder paste are heated, the solder paste is located within the solder paste layer, and the solder paste layer melts first. At this time, the solder paste remains in a solid state and supports the gap between the chip and the circuit board, allowing the gas generated by flux evaporation to be easily discharged between the chip and the circuit board. Furthermore, the solder paste layer is located on the outside of the solder paste, supported by the solder paste, resulting in a relatively large outer surface area for faster flux evaporation. This method reduces the number of air bubbles generated within the solder joint and improves the quality of the solder joint.

[0016] Preferably, a first screen printing plate is used to print solder paste dots on the circuit board by screen printing. The first screen printing plate has a first mesh hole at the contact point corresponding to the soldering area of ​​the circuit board. The area of ​​the first mesh hole is 10%-40% of the area of ​​the corresponding contact point.

[0017] By adopting the above technical solution, on the one hand, using a first screen printing plate and screen printing to print solder paste dots helps to improve the convenience of solder paste dot printing operations. On the other hand, setting the area of ​​the first mesh opening to 10%-40% controls the size of the solder paste dots and leaves sufficient space for subsequent solder paste layer printing, thereby ensuring the stability of the chip attached to the circuit board and reducing the occurrence of chip misalignment during production.

[0018] Preferably, a second screen printing plate is used to print solder paste on the circuit board by screen printing. The second screen printing plate has a second mesh opening at the contact point corresponding to the soldering area of ​​the circuit board. The area of ​​the second mesh opening is 50%-80% of the area of ​​the corresponding contact point.

[0019] By adopting the above technical solution, on the one hand, using a second screen printing plate and screen printing the solder paste layer helps to improve the convenience of the solder paste layer printing operation. On the other hand, when the chip is attached to the circuit board, under the pressure of the chip, the molten solder paste layer and solder dots will extend to the periphery. Setting the area of ​​the second mesh to 50%-80% of the corresponding contact area can not only ensure the strong soldering strength of the chip, but also reduce the occurrence of solder paste extending to adjacent contacts on the periphery, thus reducing the occurrence of short circuits between two adjacent contacts on the chip.

[0020] Preferably, the first screen printing plate is mounted on a screen printing machine, and the screen printing machine prints solder paste dots on the circuit board.

[0021] By adopting the above technical solutions, the ease of solder paste printing is further improved.

[0022] Preferably, the circuit board is cleaned before printing solder paste dots.

[0023] By adopting the above technical solutions, it is helpful to ensure the adhesion strength of solder paste dots and solder paste layers on the circuit board.

[0024] Preferably, during the heating process of solder paste dots and solder paste layers, the circuit board is evacuated by an exhaust fan.

[0025] By adopting the above technical solution, the gas generated by flux evaporation can escape from the molten solder paste more quickly, reducing the generation of bubbles in the solder joint.

[0026] Preferably, before printing the solder paste layer, an insulating varnish layer is printed in the blank area around the contacts on the circuit board, and the thickness of the insulating varnish layer is less than the thickness of the solder paste layer.

[0027] By adopting the above technical solution, when the chip is soldered onto the circuit board, the insulating varnish layer limits the molten solder paste layer and solder joints, reducing the occurrence of solder bridging and short circuits between the chip and the circuit board. Furthermore, the thickness of the insulating varnish layer is lower than the thickness of the solder paste layer, reducing the possibility of the insulating varnish layer extending peripherally and compressing the solder joint space, and helping to ensure the strength of the chip soldered onto the circuit board.

[0028] Preferably, an insulating varnish layer is printed on the blank area around the contact on the circuit board using a third screen printing plate and screen printing method; wherein, the third screen printing plate has a cutout varnish channel, which corresponds to the blank area around the contact on the circuit board.

[0029] By adopting the above technical solutions, the ease of printing insulating varnish layers can be improved.

[0030] Preferably, before printing the solder paste layer, an adhesive layer is printed in the blank area around the contacts on the circuit board, and the thickness of the adhesive layer is equal to the thickness of the solder paste layer.

[0031] By employing the above technical solution, when soldering chips onto circuit boards, the adhesive layer limits the molten solder paste layer and solder points, reducing the occurrence of solder bridging and short circuits between the chip and the circuit board. Simultaneously, the adhesive layer helps to bond the chip and the circuit board, reducing the likelihood of chip displacement and misalignment on the circuit board.

[0032] Preferably, in the adhesive printing step, the adhesive layer is spaced apart from the contact point;

[0033] Pressure is applied to the chip from one side to the other side of the circuit board before the molten solder paste and solder dots solidify.

[0034] By adopting the above technical solution, pressure is applied to the chip, which can adhere more tightly to the adhesive layer and make the adhesive layer and the contact point spaced apart, reducing the occurrence of adhesive layer extension and compression of the solder joint space. Attached Figure Description

[0035] Figure 1 This is a flowchart illustrating the contact-type chip welding process, as shown in Example 1.

[0036] Figure 2 This is a flowchart illustrating the contact-type chip welding process, which is the main feature of Example 2.

[0037] Figure 3 This is a flowchart illustrating the contact-type chip welding process in Example 3. Detailed Implementation

[0038] The present application will be further described in detail below with reference to the accompanying drawings.

[0039] In related technologies, the circuit board soldering area and the chip are generally arranged in an array with several contacts, and the contacts on the circuit board soldering area and the chip correspond one-to-one.

[0040] This application discloses a contact-type chip welding process.

[0041] Example 1:

[0042] See Figure 1 The contact-type chip bonding process includes the following steps:

[0043] S1. Cleaning Operation. Clean the circuit board. In this embodiment, the circuit board can be cleaned by blowing air with an ion fan or by rolling a cleaning roller over the circuit board.

[0044] S2. Printing solder paste dots. Using a first screen printing plate and screen printing method, solder paste dots are printed at each contact point in the circuit board soldering area. The first screen printing plate has first mesh openings, each corresponding to a contact point in the circuit board soldering area. The area of ​​the first mesh opening is 10%-40% of the corresponding contact area; preferably, the area of ​​the first mesh opening is 25% of the corresponding contact area.

[0045] Furthermore, the first screen printing plate can be mounted on a screen printing machine, which then prints solder paste dots on the circuit board, thereby improving the efficiency of solder paste dot printing.

[0046] S3. Melting Solder Paste Points. The circuit board is fed into the reflow soldering machine, where the reflow soldering machine heats the solder paste points, causing them to melt. Simultaneously, an exhaust fan is used to evacuate air from the circuit board inside the reflow soldering machine. In this embodiment, the exhaust fan is used.

[0047] S4. Forming Solder Joints. The circuit board is sent out of the reflow soldering machine, and the molten solder paste on the circuit board is cooled, forming solder joints at the contacts. In this embodiment, the circuit board and the molten solder paste can be cooled by placing the circuit board still, or by using any of the following: a fan, blower, or air cooler.

[0048] S5, Printed solder paste layer.

[0049] A second screen printing plate is used to print solder paste layers at each contact point within the circuit board's soldering area using a screen printing method, ensuring that the solder paste layer covers the solder points. The second screen printing plate has second mesh openings, each corresponding to a contact point in the circuit board's soldering area. The area of ​​the second mesh opening is 50%-80% of the corresponding contact area; preferably, the area of ​​the second mesh opening is 70% of the corresponding contact area.

[0050] Furthermore, a second screen printing plate can be installed on a screen printing machine, which then prints the solder paste layer on the circuit board, thereby improving the efficiency of solder paste dot printing.

[0051] S6. Chip Placement. A robotic arm can be used to place the chip onto the soldering area of ​​the circuit board, so that the chip's contacts are in contact with the solder paste layer; at this time, the solder paste layer can relatively stably adhere the chip to the circuit board.

[0052] S7. Soldering operation. The circuit board and chip are fed into the reflow soldering machine, where the reflow soldering machine heats the solder paste layer and solder joints, causing them to melt. Simultaneously, an exhaust fan is used to evacuate air from the circuit board inside the reflow soldering machine. In this embodiment, the exhaust fan is used.

[0053] S8. Curing Operation. The soldering area of ​​the circuit board is cooled, causing the molten solder paste layer and solder points to solidify and form solder joints, thus soldering the chip onto the circuit board. In this embodiment, the circuit board and molten solder paste can be cooled by placing the circuit board still, or by using any of the following methods: fan, blower, or air cooler.

[0054] Example 2:

[0055] See Figure 2 The contact-type chip bonding process includes the following steps:

[0056] S1. Cleaning Operation. Clean the circuit board. In this embodiment, the circuit board can be cleaned by blowing air with an ion fan or by rolling a cleaning roller over the circuit board.

[0057] S2. Printing solder paste dots. Using a first screen printing plate and screen printing method, solder paste dots are printed at each contact point in the circuit board soldering area. The first screen printing plate has first mesh openings, each corresponding to a contact point in the circuit board soldering area. The area of ​​the first mesh opening is 10%-40% of the corresponding contact area; preferably, the area of ​​the first mesh opening is 25% of the corresponding contact area.

[0058] Furthermore, the first screen printing plate can be mounted on a screen printing machine, which then prints solder paste dots on the circuit board, thereby improving the efficiency of solder paste dot printing.

[0059] S3. Melting Solder Paste Points. The circuit board is fed into the reflow soldering machine, where the reflow soldering machine heats the solder paste points, causing them to melt. Simultaneously, an exhaust fan is used to evacuate air from the circuit board inside the reflow soldering machine. In this embodiment, the exhaust fan is used.

[0060] S4. Forming Solder Joints. The circuit board is sent out of the reflow soldering machine, and the molten solder paste on the circuit board is cooled, forming solder joints at the contacts. In this embodiment, the circuit board and the molten solder paste can be cooled by placing the circuit board still, or by using any of the following: a fan, blower, or air cooler.

[0061] S5. Printing Insulating Varnish Layer. An insulating varnish layer is printed on the blank area around the contacts of the circuit board using a third screen printing plate. The insulating varnish layer is a high-temperature insulating varnish layer. The third screen printing plate has perforated varnish channels, which correspond to the blank area around the contacts of the circuit board.

[0062] Furthermore, a third screen printing plate can be installed on a screen printing machine, which will then print the insulating varnish layer on the circuit board, thereby improving the efficiency of printing the insulating varnish layer.

[0063] S6, Printed solder paste layer.

[0064] A second screen printing plate is used to print solder paste layers at each contact point within the circuit board's soldering area using a screen printing method. The thickness of the solder paste layer is greater than the thickness of the insulating varnish layer, ensuring that the solder paste layer covers the solder joints. The second screen printing plate has second mesh openings, each corresponding to a contact point in the circuit board's soldering area. The area of ​​the second mesh opening is 50%-80% of the corresponding contact area; preferably, the area of ​​the second mesh opening is 70% of the corresponding contact area.

[0065] Furthermore, a second screen printing plate can be installed on a screen printing machine, which then prints the solder paste layer on the circuit board, thereby improving the efficiency of solder paste dot printing.

[0066] It should be noted that when designing this contact-type chip soldering process, the thickness of the solder paste layer should be prioritized, as it is of great importance. The thickness of the insulating varnish layer can be less than the predetermined solder paste layer thickness.

[0067] S7. Chip Placement. A robotic arm can be used to place the chip onto the soldering area of ​​the circuit board, so that the chip's contacts are in contact with the solder paste layer; at this time, the solder paste layer can relatively stably adhere the chip to the circuit board.

[0068] S8. Soldering operation. The circuit board and chip are fed into the reflow soldering machine, where the reflow soldering machine heats the solder paste layer and solder joints, melting them, and also heats and dries the insulating varnish layer. Simultaneously, an exhaust fan is used to evacuate air from the circuit board inside the reflow soldering machine. In this embodiment, the exhaust fan is used.

[0069] S9. Curing Operation. The soldering area of ​​the circuit board is cooled, causing the molten solder paste layer and solder points to solidify and form solder joints, thus soldering the chip onto the circuit board. In this embodiment, the circuit board and molten solder paste can be cooled by placing the circuit board still, or by using any of the following methods: fan, blower, or air cooler.

[0070] Example 3:

[0071] See Figure 3 The difference between this embodiment and Embodiment 3 is as follows:

[0072] S5. Printed Adhesive Layer. Using a fourth screen printing plate and screen printing method, an adhesive layer is printed on the blank area around the contacts on the circuit board. The adhesive layer uses high-temperature resistant adhesive and is spaced apart from the contacts. The fourth screen printing plate has cutout adhesive channels that correspond to the blank area around the contacts on the circuit board.

[0073] Furthermore, a fourth screen printing plate can be installed on a screen printing machine, which can then print the adhesive layer on the circuit board, thereby improving the efficiency of adhesive layer printing.

[0074] To reduce the likelihood of the adhesive layer blocking the discharge of gases generated by flux evaporation, the adhesive layer is segmented, with intervals reserved to allow for the discharge of gases generated by flux evaporation.

[0075] S6, Printed solder paste layer.

[0076] A second screen printing plate is used to print solder paste layers at each contact point within the circuit board's soldering area using a screen printing method. The thickness of the solder paste layer is equal to or greater than that of the adhesive layer, ensuring that the solder paste layer covers the solder joint. The second screen printing plate has second mesh openings, each corresponding to a contact point in the circuit board's soldering area. The area of ​​the second mesh opening is 50%-80% of the corresponding contact area; preferably, the area of ​​the second mesh opening is 70% of the corresponding contact area.

[0077] Furthermore, a second screen printing plate can be installed on a screen printing machine, which then prints the solder paste layer on the circuit board, thereby improving the efficiency of solder paste dot printing.

[0078] It should be noted that when designing this contact-type chip soldering process, the thickness of the solder paste layer should be prioritized, as it is of great importance. The thickness of the adhesive layer should be equal to the predetermined thickness of the solder paste layer.

[0079] S7. Chip Placement. A robotic arm can be used to place the chip onto the soldering area of ​​the circuit board, so that the chip's contacts come into contact with the solder paste layer and the adhesive layer. At this time, the solder paste layer and the adhesive layer work together to stably adhere the chip to the circuit board.

[0080] S8. Soldering operation. The circuit board and chip are fed into the reflow soldering machine, where the reflow soldering machine heats the solder paste layer and solder joints, causing them to melt. Simultaneously, an exhaust fan is used to remove air from the circuit board inside the reflow soldering machine. In this embodiment, the exhaust fan is used.

[0081] S9. Curing Process. First, pressure is applied to the chip, pressing it firmly onto the circuit board so that the chip can make relatively close contact with the molten solder paste and adhesive layer. Then, the soldering area of ​​the circuit board is cooled, causing the molten solder paste layer and solder joints to solidify and form solder joints, thus soldering the chip onto the circuit board. In this embodiment, the circuit board and molten solder paste can be cooled by placing the circuit board still, or by using any of the following: a fan, blower, or air cooler.

[0082] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A contact chip soldering process, characterized by, The method comprises the following steps: printing a tin paste point on the contact in the soldering area of the circuit board; heating the tin paste point to melt the tin paste point; cooling the melted tin paste point on the circuit board to form a tin point at the contact; printing a tin paste layer on the contact in the soldering area of the circuit board, and arranging the tin point in the tin paste layer; attaching the chip to the soldering area of the circuit board to make the contact of the chip contact the tin paste layer; heating the tin paste layer and the tin point to melt the tin paste layer and the tin point; cooling the soldering area of the circuit board to make the melted tin paste layer and tin point solidify and form a soldering point, and weld the chip to the circuit board; during the heating of the tin paste point and the heating of the tin paste layer and the tin point, the circuit board is subjected to air extraction by an air extraction device.

2. A contact chip soldering process according to claim 1, characterized in that: The tin paste point is printed on the circuit board by screen printing using a first screen printing plate, wherein the first screen printing plate is provided with a first mesh hole corresponding to the contact in the soldering area of the circuit board, and the area of the first mesh hole is 10%-40% of the area of the corresponding contact.

3. A contact chip soldering process as claimed in claim 1, characterized in that: The tin paste layer is printed on the circuit board by screen printing using a second screen printing plate, wherein the second screen printing plate is provided with a second mesh hole corresponding to the contact in the soldering area of the circuit board, and the area of the second mesh hole is 50%-80% of the area of the corresponding contact.

4. A contact chip soldering process according to claim 2, characterized in that: The first screen printing plate is installed on a screen printing machine, and the tin paste point on the circuit board is printed by the screen printing machine.

5. A contact chip soldering process as claimed in claim 1, wherein: The circuit board is cleaned before the tin paste point is printed.

6. A contact chip soldering process as claimed in claim 1, characterized in that: Before the tin paste layer is printed, an insulating paint layer is printed on the blank area around the contact on the circuit board, and the thickness of the insulating paint layer is less than the thickness of the tin paste layer.

7. A contact chip soldering process according to claim 6, characterized in that: The insulating paint layer is printed on the blank area around the contact on the circuit board by screen printing using a third screen printing plate, wherein the third screen printing plate is provided with a hollow paint path corresponding to the blank area around the contact on the circuit board.

8. A contact chip soldering process as claimed in claim 1, characterized in that: Before the tin paste layer is printed, a glue layer is printed on the blank area around the contact on the circuit board, and the thickness of the glue layer is equal to the thickness of the tin paste layer.

9. The contact chip soldering process according to claim 8, wherein: during the glue printing step, the glue layer is arranged to be spaced apart from the contact; before the melted tin paste layer and tin point solidify, the chip is pressed from one side of the chip to the other side of the circuit board.

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