Method for controlling temperature of BGA (Ball Grid Array) device by using tool in reflow soldering process

Abstract

The invention relates to a method for controlling the temperature of a BGA device through a tool in the reflow soldering process, and belongs to the technical field of integrated circuit manufacturing. According to the size of the BGA device and the expected cooling effect, a tool manufacturing material, the tool thickness L and the air gap thickness d are selected; before reflow soldering, the BGA device body and a welding spot area are covered with the tool; the tool is of a semi-surrounding structure, and after the tool covers the BGA device body and the welding spot area, the tool and the printed circuit board below form a fully-closed structure. The invention provides a specific accurate calculation and control method for cooling by adopting the tool, and through the thermal resistance design of the tool, accurate cooling of the BGA device body within 20 DEG C is realized, and overheating of the device is avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated circuit manufacturing, and in particular relates to a method for controlling the temperature of a BGA device by using a tool during a reflow soldering process. Background Art

[0002] As electronic products develop towards multifunctionality and high density, the number of chips designed for printed circuit board assemblies has increased, and some device manufacturers have conflicting soldering requirements. During the reflow soldering process of integrated circuits, the soldering quality of BGA components directly affects the reliability of the product. In traditional reflow soldering processes, the overall thermal uniformity of BGA components is poor, especially for BGA components in ceramic packages. Due to their large heat capacity, this can easily lead to excessively high device temperatures and insufficient solder joint temperatures, thus affecting soldering quality. In existing technologies, methods such as adding heat sinks or adjusting the furnace temperature curve are commonly used to control temperature, but these methods have the following problems:

[0003] 1. Heat sinks increase process complexity and make it difficult to accurately control temperature;

[0004] 2. Adjusting the furnace temperature curve will affect the welding quality of other components and make it difficult to achieve local temperature control.

[0005] Therefore, there is an urgent need for a tooling and design method that can accurately control the temperature of the BGA device body while ensuring that the solder joint temperature meets the reflow soldering requirements. Summary of the Invention

[0006] (1) Technical issues to be resolved

[0007] The technical problem to be solved by the present invention is how to provide a method for controlling the temperature of BGA devices using tooling during the reflow soldering process, so as to solve the problems that the heat sink increases the process complexity and makes it difficult to accurately control the temperature; adjusting the furnace temperature curve affects the soldering quality of other devices and makes it difficult to achieve local temperature control.

[0008] (2) Technical solution

[0009] In order to solve the above technical problems, the present invention proposes a method for controlling the temperature of a BGA device using a tool during a reflow soldering process, the method comprising the following steps:

[0010] S1. Select the tooling material, tooling thickness L, and air gap thickness d based on the size of the BGA device and the expected cooling effect.

[0011] S2. Before reflow soldering, the tooling is used to cover the BGA device body and solder joint area. The tooling is a semi-enclosed structure. After the tooling covers the BGA device body and solder joint area, it forms a fully enclosed structure with the printed circuit board below.

[0012] S3, performing reflow soldering process.

[0013] (3) Beneficial effects

[0014] The present invention proposes a method for controlling the temperature of a BGA device using a tool during a reflow soldering process. The present invention has the following beneficial effects:

[0015] 1. The present invention provides a specific and precise calculation and control method for cooling the BGA device body by using a tool. By designing the thermal resistance of the tool, the BGA device body can be accurately cooled within 20°C to avoid overheating of the device.

[0016] 2. The present invention adopts a fully enclosed design to ensure that the temperature of the soldering point area meets the welding requirements, and the welding is uniform in all directions, thereby improving the welding quality;

[0017] 3. The tooling structure is simple, easy to manufacture and install, and suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The heat conduction sequence before and after the use of the tooling of the present invention; (a) before the use of the tooling; (b) after the use of the tooling;

[0019] Figure 2 The temperature curve before and after using the tooling;

[0020] Figure 3 It is a structural schematic diagram of the tooling of the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose, content and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below with reference to the accompanying drawings and examples.

[0022] The present invention relates to the technical field of integrated circuit manufacturing, and in particular to a tool and a design method thereof for controlling the temperature of risk devices during the reflow soldering process of high-density printed circuit board components, and is particularly suitable for the soldering process of ceramic packaged BGA devices.

[0023] The present invention aims to provide a method for controlling the temperature of BGA components during reflow soldering using a tool. This method, through a fully enclosed tool design and its thermal resistance calculation model, achieves precise cooling of the BGA component body while ensuring that the solder joint temperature meets soldering requirements. This method offers advantages such as a simple structure, ease of manufacture, and wide applicability, significantly improving the soldering quality of BGA components. By utilizing the tool's thermal resistance design, this method achieves precise cooling of the BGA component body while ensuring that the solder joint temperature meets soldering requirements.

[0024] 1. The present invention provides a method for controlling the temperature of a BGA device using a tool during a reflow soldering process, the method comprising:

[0025] S1. Select the tooling material, tooling thickness L, and air gap thickness d based on the size of the BGA device and the expected cooling effect.

[0026] Among them, the cooling temperature can reach 0-20℃.

[0027] Among them, the expected cooling effect is determined according to the thermal characteristics of the BGA device, and then the target value of the thermal resistance on the tooling side is determined; by adjusting the tooling manufacturing material, tooling thickness L and air gap thickness d, precise control of the thermal resistance on the tooling side is achieved.

[0028] S2. Before reflow soldering, the tooling is used to cover the BGA device body and solder joint area. The tooling is a semi-enclosed structure. After the tooling covers the BGA device body and solder joint area, it forms a fully enclosed structure with the printed circuit board below.

[0029] When in use, the thermal insulation tooling is buckled downward onto the BGA device body and solder joint area that need to be insulated, and the thermal insulation tooling does not contact the BGA device body.

[0030] Among them, the tooling material is synthetic stone or polyimide, which has low thermal conductivity characteristics;

[0031] Among them, an air gap is set between the tooling and the surface of the BGA device to further increase the thermal resistance. Due to the limited space on the high-density printed circuit board, the distance between the BGA device and the tooling is the same and fixed on all sides. The distance between the top surface of the BGA device and the tooling, that is, the air gap thickness d, can be adjusted.

[0032] S3, performing reflow soldering process.

[0033] 2. Thermal resistance design method

[0034] -Thermal resistance R when reflow soldering is not performed using a tool 原热阻 , is the device convection heat transfer resistance R 器件对流 and the thermal resistance R on the PCB side PCB侧 The parallel value is calculated as follows:

[0035]

[0036] in:

[0037]

[0038] h1 is the convection heat transfer coefficient in the reflow furnace, A 器件表面积 is the surface area of ​​the device, k PCB is the thermal conductivity of the printed circuit board (usually 0.2 to 0.4 W / (m·K)), A 印制板面积 is the bottom area of ​​the printed circuit board, L PCB is the thickness of the printed circuit board.

[0039] When using a fixture, the thermal resistance on the PCB side is the same as when it is not used. On the device side, the heat transfer from hot air to the device is replaced by convection heat transfer from hot air to the fixture. The fixture, air, and device are both conducting heat transfer and heat radiation. The thermal resistance on the fixture side is composed of the thermal resistance of the reflow soldering to the fixture, the thermal resistance of the material, the thermal resistance of the air gap, and the natural convection heat transfer of the device. The calculation formula is:

[0040] R 工装侧 =R 工装对流 +R material +R air +R 自然换热

[0041] in:

[0042]

[0043] L is the tooling thickness, k material is the thermal conductivity of the tooling material, d is the thickness of the air gap, k air is the thermal conductivity of air, A is the area covered by the tooling, and A 工装表面积 is the surface area of ​​the tooling, h2 is the natural convection heat transfer coefficient

[0044] By adjusting the tooling material, tooling thickness L and air gap thickness d, the thermal resistance of the tooling can be controlled to achieve precise cooling of the BGA device body.

[0045] 3. Calculation of cooling effect

[0046] -Total thermal resistance R when using the fixture for reflow soldering total is the thermal resistance of the tooling R 工装侧 and the printed circuit board thermal resistance R PCB侧 The parallel value is calculated as follows:

[0047]

[0048] The cooling effect is reflected by the percentage of temperature reduction when using the tooling for reflow soldering compared to when not using the tooling for reflow soldering. The cooling percentage calculation formula is:

[0049]

[0050] Example 1:

[0051] The present invention is described in detail below with reference to the embodiments:

[0052] 1. Tooling design

[0053] -The tooling material is synthetic stone, with thermal conductivity k material =0.25W / (m·K);

[0054] - Tooling thickness L = 0.0025m, air gap thickness d = 0.0005mm;

[0055] -Tooling coverage area A = 0.000625m 2 Here, the surface area of ​​the tooling and the surface area of ​​the device are approximated as the tooling coverage area;

[0056] -The forced convection heat transfer coefficient of the reflow oven h1≈43W / (m·K).

[0057] -Natural convection heat transfer coefficient h2≈10W / (m·K)

[0058] - Thermal conductivity k of printed circuit board PCB =0.3W / (m·K)

[0059] -PCB thickness L PCB =0.002mm

[0060] -PCB area A PCB =0.03m 2 .

[0061] 2. Thermal resistance calculation

[0062] -Convection heat transfer resistance of tooling:

[0063]

[0064] -Material thermal resistance:

[0065]

[0066] -Air gap thermal resistance:

[0067]

[0068] -Device natural convection heat transfer thermal resistance:

[0069]

[0070] -Total thermal resistance on tooling side:

[0071] R 工装侧 =R 对流换热 +R material +R air +R 自然换热 =237.45K / W

[0072] -Original device convection heat transfer thermal resistance:

[0073]

[0074] -PCB convection heat transfer thermal resistance:

[0075]

[0076] -PCB thermal resistance:

[0077]

[0078] 3. Cooling effect

[0079] -Original thermal resistance:

[0080]

[0081] -Total thermal resistance:

[0082]

[0083] -Temperature reduction percentage:

[0084]

[0085] Beneficial effects of the present invention:

[0086] 1. The present invention provides a specific and precise calculation and control method for cooling the BGA device body by using a tool. By designing the thermal resistance of the tool, the BGA device body can be accurately cooled within 20°C to avoid overheating of the device.

[0087] 2. The present invention adopts a fully enclosed design to ensure that the temperature of the soldering point area meets the welding requirements, and the welding is uniform in all directions, thereby improving the welding quality;

[0088] 3. The tooling structure is simple, easy to manufacture and install, and suitable for large-scale production.

[0089] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for controlling the temperature of a BGA device using a tool during a reflow soldering process, characterized in that: The method comprises the following steps: S1. Select the tooling material, tooling thickness L, and air gap thickness d based on the size of the BGA device and the expected cooling effect. S2. Before reflow soldering, the tooling is used to cover the BGA device body and solder joint area. The tooling is a semi-enclosed structure. After the tooling covers the BGA device body and solder joint area, it forms a fully enclosed structure with the printed circuit board below. S3, performing reflow soldering process.

2. The method for controlling the temperature of a BGA device using a tool during a reflow soldering process according to claim 1, wherein: In S1, the expected cooling effect is determined based on the thermal characteristics of the BGA device, and then the target value of the thermal resistance on the tooling side is determined; by adjusting the tooling material, tooling thickness L and air gap thickness d, precise control of the thermal resistance on the tooling side is achieved.

3. The method for controlling the temperature of a BGA device using a tool during a reflow soldering process according to claim 1, wherein: In the above-mentioned S2, when in use, the heat insulating tool is buckled downward onto the BGA device body and solder joint area that need to be insulated, and the heat insulating tool is not in contact with the BGA device body.

4. The method for controlling the temperature of a BGA device using a tool during a reflow soldering process according to claim 1, wherein: In the above-mentioned S2, the tooling material is synthetic stone or polyimide.

5. The method for controlling the temperature of a BGA device using a tool during a reflow soldering process according to claim 1, wherein: In S2, an air gap is provided between the tooling and the surface of the BGA device to increase thermal resistance. The distances between the BGA device and the tooling are the same and fixed. The distance between the upper surface of the BGA device and the tooling, i.e., the thickness d of the air gap, can be adjusted.

6. The method for controlling the temperature of a BGA device using a tool during a reflow soldering process according to any one of claims 1 to 5, wherein: In S1, the cooling effect is reflected by the cooling percentage of reflow soldering performed with the tooling compared to reflow soldering performed without the tooling. The cooling percentage is calculated as follows: Among them, R 原热阻 R is the thermal resistance of the device when reflow soldering is not performed using a tool. total is the total thermal resistance when using the fixture for reflow soldering.

7. The method for controlling the temperature of a BGA device using a tool during a reflow soldering process according to claim 6, wherein: The total thermal resistance R when using the tooling for reflow soldering total is the thermal resistance of the tooling R 工装侧 and the printed circuit board thermal resistance R PCB The parallel value is calculated as follows:

8. The method for controlling the temperature of a BGA device using a tool during a reflow soldering process according to claim 7, wherein: When using a fixture, the thermal resistance on the PCB side is the same as when not using a fixture. On the device side, the direct convection heat transfer from hot air to the device is replaced by convection heat transfer from hot air to the fixture. The fixture, air, and device are conducting heat transfer and heat radiation. The thermal resistance on the tooling side is composed of the convection heat transfer resistance of the reflow soldering to the tooling, the thermal resistance of the material, the thermal resistance of the air gap, and the natural convection heat transfer of the device.

9. The method for controlling the temperature of a BGA device using a tool during a reflow soldering process according to claim 7, wherein: R 工装侧 =R 工装对流 +R material +R air +R 自然换热 in: L is the tooling thickness, k material is the thermal conductivity of the tooling material, d is the thickness of the air gap, k air is the thermal conductivity of air, A is the area covered by the tooling, and A 工装表面积 is the surface area of ​​the tooling, and h2 is the natural convection heat transfer coefficient.

10. The method for controlling the temperature of a BGA device using a tool during a reflow soldering process according to claim 9, wherein: R 原热阻 is the device convection heat transfer resistance R 器件对流 and the thermal resistance R on the PCB side PCB侧 The parallel value is calculated as follows: in: h1 is the convection heat transfer coefficient in the reflow furnace, A 器件表面积 is the surface area of ​​the device, k PCB is the thermal conductivity of the printed circuit board, A 印制板面积 is the bottom area of ​​the printed circuit board, L PCB is the thickness of the printed circuit board.

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