Welding method for chip positioning

Abstract

The invention discloses a welding method for chip positioning, and belongs to the technical field of welding processes, the quality, reliability and durability of welding spots can be remarkably improved through secondary welding, especially in high-requirement application scenes, the advantages of secondary welding are more obvious, the defects in the welding process can be overcome, and the welding quality is improved. The production efficiency and the long-term stability of the element can be improved, more complex design requirements are met, and the mode is generally used for ensuring the quality of welding spots, improving the reliability or supplementing special function requirements; the welding reliability is effectively improved, the welding spots are reinforced, the welding spots are insufficient possibly due to improper temperature control, insufficient soldering tin amount, too short welding time and the like in the primary welding process, soldering tin can be reheated and supplemented through secondary welding, it is ensured that the welding spots are sufficient and uniform, the risks of insufficient welding and cold welding are reduced, and the welding quality is improved. And meanwhile, welding defects are effectively eliminated.

Description

Technical Field

[0001] The invention relates to the technical field of welding technology, in particular to a chip positioning welding method. Background Art

[0002] The chip diode, also known as the crystal diode, is an electronic device with unidirectional current conduction. A PN junction and two lead terminals are set inside the semiconductor diode. This diode has unidirectional current transduction according to the direction of the applied voltage. Generally speaking, the chip crystal diode is a PN junction interface formed by sintering a P-type semiconductor and an N-type semiconductor. A space charge layer is formed on both sides of the interface to form a self-built electric field. When the applied voltage is zero, the diffusion current caused by the concentration difference of the carriers on both sides of the PN junction and the drift current caused by the self-built electric field are equal and are in an electrical equilibrium state.

[0003] The prior art is one-time welding. After the parts are assembled, a single welding step is used to complete all the welding points at one time. During assembly, the chip is prone to displacement, resulting in low reliability of subsequent products. At the same time, during the existing one-time welding process, due to uneven temperature changes, residual stress may be generated inside the welding area or at the welding joint. These stresses may cause cracks in the chip or even cause product failure. In addition, in the current packaging structure, there is a possibility that the primary welding piece and the chip will be shifted when placing the secondary welding piece, thereby causing chip displacement, resulting in increased welding contact resistance, affecting the electrical performance and reliability of the product. Therefore, a chip positioning welding method is proposed. Summary of the invention

[0004] The object of the present invention is to provide a chip positioning welding method to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a chip positioning welding method, comprising the following steps:

[0006] S1, one-time welding;

[0007] S11, first place the frame on the upper cover of the fixture;

[0008] S12, loading a primary soldering sheet on the frame soldering area, and then placing a chip on the primary soldering sheet;

[0009] S13, placing a secondary soldering sheet, a small soldering sheet and a connecting sheet on the chip in sequence;

[0010] S14, placing the graphite fixture filled with components into a vacuum welding furnace to complete a welding process;

[0011] S2, secondary welding;

[0012] S21. Preparation and implementation of secondary welding: Before secondary welding, the welding parts should be inspected and prepared in detail to ensure that the welding quality meets the requirements. The specific preparation work includes:

[0013] S211. Initial welding quality inspection: Check whether the weld has defects through non-destructive testing;

[0014] S212, welding part cleaning: clean the impurities in the initial welding part to prevent affecting the quality of the secondary welding;

[0015] S213, Welding heat affected zone assessment: Assess the state of the heat affected zone to avoid overheating or improper cooling that may lead to material performance degradation;

[0016] S214. Select suitable welding process: select suitable welding process and equipment according to welding materials, welding structure and use requirements;

[0017] S215, controlling welding heat input;

[0018] S216, controlling the welding sequence and welding position: during the secondary welding, selecting an appropriate welding sequence and welding position according to the shape, structure and position of the welding workpiece;

[0019] S217, start welding from the low stress area and gradually transition to the high stress area;

[0020] S218, cooling control: control the cooling rate of each welding layer to avoid thermal cracks;

[0021] S22, post-weld treatment;

[0022] S23. Quality inspection and acceptance.

[0023] As a further preferred embodiment of the present technical solution: in S13, the small welding piece is used to weld the lead and the connecting piece, and in S14, after one welding is completed, the frame, the primary welding piece, the chip, the secondary welding piece, the small welding piece and the connecting piece are integrated.

[0024] As a further preferred embodiment of the present technical solution: in S211, the nondestructive testing includes X-ray testing or ultrasonic testing, and when defects exist, the severity of the defects is evaluated and it is confirmed whether to perform repairs.

[0025] As a further preferred embodiment of the present technical solution: in S212, the impurities to be cleaned include oil stains, rust or oxide layers, and the cleaning method adopted is steel brush, grinding wheel, mechanical grinding or chemical cleaning.

[0026] As a further preferred embodiment of the present technical solution: in S213, the heat input of the secondary welding should be properly controlled to avoid secondary damage to the original welding quality.

[0027] As a further preferred embodiment of the present technical solution: in S215, during the secondary welding process, the heat input needs to be properly controlled. Too high heat input will result in an excessively large heat-affected zone of the welded joint, thereby affecting the mechanical properties of the material;

[0028] Among them, measures to control welding heat input include adjusting welding current or welding voltage or welding speed parameters, adopting layered welding method, controlling heat input during each welding, and avoiding the generation of an excessively large heat-affected zone.

[0029] As a further preferred embodiment of the present technical solution: in S216, an incorrect welding sequence may lead to uneven distribution of thermal stress, thereby causing deformation or cracking.

[0030] As a further preferred embodiment of the present technical solution: in S22, post-weld processing is used to eliminate stress generated during welding and improve welding quality.

[0031] As a further preferred embodiment of the present technical solution: the post-weld treatment method includes heat treatment, stress relief treatment and surface treatment.

[0032] As a further preferred embodiment of the present technical solution: in S23, quality inspection and acceptance are used to ensure that the welding quality meets the design requirements.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The secondary welding in the present invention can significantly improve the quality, reliability and durability of solder joints. Especially in high-demand application scenarios, the advantages of secondary welding are more obvious. It can not only supplement and improve the deficiencies in the welding process, but also improve production efficiency and long-term stability of components, and adapt to more complex design requirements. This method is usually used to ensure the quality of solder joints, improve reliability or supplement special functional requirements;

[0035] 2. The present invention can use secondary welding to repair welding defects: such as incomplete penetration of the weld, cracks, pores and slag inclusions, strengthen welding: increase weld thickness or strength, improve load-bearing capacity, and ensure appearance quality: improve welding appearance, remove external defects or irregular shapes;

[0036] 3. The present invention effectively improves welding reliability and strengthens solder joints: In the initial welding process, the solder joints may be insufficient due to improper temperature control, insufficient soldering, too short welding time, etc. Through secondary welding, the solder can be reheated and replenished to ensure that the solder joints are sufficient and uniform, reduce the risk of false solder joints and cold solder joints, and effectively eliminate welding defects: such as false solder joints, leaking solder joints, bubbles, etc. Secondary welding can effectively solve these problems, improve the electrical contact performance and mechanical strength of the solder joints, and improve the quality of the solder joints;

[0037] 4. The present invention effectively removes oxides from solder joints: secondary welding helps to remove oxides on the surface of solder joints, ensuring good contact of solder joints. During the secondary heating process, oxides on the solder surface are removed, the electrical conductivity and mechanical connectivity of the solder joints are improved, and solder joint stress can be reduced: after the initial welding, temperature changes may cause stress concentration near the solder joints. Secondary welding can relieve these stresses, reduce the risk of solder joint cracking, and improve production efficiency;

[0038] 5. In the initial welding process of the present invention, due to temperature control, uneven welding may occur. The secondary welding can optimize the components through more precise temperature control technology to ensure uniform heat distribution during the welding process and avoid overheating or underheating. At the same time, the present invention can improve the heat dissipation effect: For some high-power SMD diodes, secondary welding can sometimes help ensure better heat dissipation, ensure the stability and long-term reliability of the components during operation, and can effectively repair damaged solder joints: If bad solder joints appear in the first round of welding, secondary welding can be used as a repair method to avoid problems with the product in later use. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A schematic diagram of the operation flow of a chip positioning welding method of the present invention;

[0040] Figure 2 A schematic diagram of the structure of a single welding process in a chip positioning welding method of the present invention;

[0041] Figure 3 It is a schematic diagram of the architecture of secondary welding in a chip positioning welding method of the present invention. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0043] Example

[0044] See also Figure 1-Figure 3 The present invention provides a technical solution: a chip positioning welding method, comprising the following steps:

[0045] S1, one-time welding;

[0046] S11, first place the frame on the upper cover of the fixture;

[0047] S12, loading a primary soldering sheet on the frame soldering area, and then placing a chip on the primary soldering sheet;

[0048] S13, placing a secondary soldering sheet, a small soldering sheet and a connecting sheet on the chip in sequence;

[0049] S14, placing the graphite fixture filled with components into a vacuum welding furnace to complete a welding process;

[0050] S2, secondary welding;

[0051] S21. Preparation and implementation of secondary welding: Before secondary welding, the welding parts should be inspected and prepared in detail to ensure that the welding quality meets the requirements. The specific preparation work includes:

[0052] S211. Initial welding quality inspection: Check whether the weld has defects through non-destructive testing;

[0053] S212, welding part cleaning: clean the impurities in the initial welding part to prevent affecting the quality of the secondary welding;

[0054] S213, Welding heat affected zone assessment: Assess the state of the heat affected zone to avoid overheating or improper cooling that may lead to material performance degradation;

[0055] S214. Select suitable welding process: select suitable welding process and equipment according to welding materials, welding structure and use requirements;

[0056] S215, controlling welding heat input;

[0057] S216, controlling the welding sequence and welding position: during the secondary welding, selecting an appropriate welding sequence and welding position according to the shape, structure and position of the welding workpiece;

[0058] S217, start welding from the low stress area and gradually transition to the high stress area;

[0059] S218, cooling control: control the cooling rate of each welding layer to avoid thermal cracks;

[0060] S22, post-weld treatment;

[0061] S23. Quality inspection and acceptance.

[0062] In this embodiment, specifically: in S13, the small welding piece is used to weld the lead and the connecting piece, and in S14, after one welding is completed, the frame, the primary welding piece, the chip, the secondary welding piece, the small welding piece and the connecting piece are integrated.

[0063] In this embodiment, specifically: in S211, nondestructive testing includes X-ray testing or ultrasonic testing, and when defects exist, the severity of the defects is evaluated and it is confirmed whether to repair them.

[0064] In this embodiment, specifically: in S212, the impurities cleaned include oil stains, rust or oxide layers, and the cleaning method adopted is steel brush, grinding wheel, mechanical grinding or chemical cleaning.

[0065] In this embodiment, specifically: in S213, the heat input of the secondary welding should be properly controlled to avoid secondary damage to the original welding quality.

[0066] In this embodiment, specifically: in S215, during the secondary welding process, the heat input needs to be properly controlled. Excessive heat input will result in an excessively large heat affected zone (HAZ) of the weld joint, thereby affecting the mechanical properties of the material. In the welding of high-strength steel or certain special materials, excessive control of heat input requires special attention;

[0067] Among them, measures to control welding heat input include adjusting welding current or welding voltage or welding speed parameters, adopting layered welding method, controlling heat input during each welding, and avoiding the generation of an excessively large heat-affected zone.

[0068] In this embodiment, specifically: in S216, an incorrect welding sequence may lead to uneven distribution of thermal stress, thereby causing deformation or cracking.

[0069] In this embodiment, specifically: in S22, the post-weld processing is used to eliminate the stress generated during the welding process and improve the welding quality.

[0070] In this embodiment, specifically: the post-welding treatment method includes heat treatment, stress relief treatment and surface treatment;

[0071] Among them, heat treatment: annealing, normalizing or solution treatment of welded parts to eliminate internal stress in the heat-affected zone of welding and improve the mechanical properties of welded joints;

[0072] Stress relief treatment: When large residual stress is generated during welding, stress relief annealing is required;

[0073] Surface treatment: including removing welding spatter, grinding welds and surface spraying, etc., to improve the corrosion resistance and appearance quality of the welding parts.

[0074] In this embodiment, specifically: in S23, quality inspection and acceptance are used to ensure that the welding quality meets the design requirements.

[0075] In this embodiment, specifically: secondary welding is a very delicate process that requires a high degree of control. It is usually necessary to select appropriate welding processes and technical parameters based on the specific circumstances. Through effective preparation, control of the welding process, post-weld processing and quality inspection, the strength, stability and service life of the welded structure can be ensured. During the welding process, the control of heat input, welding sequence, selection of welding materials and subsequent processing all require careful operation.

[0076] Working principle: For one-time welding, first place the frame on the upper cover of the jig, load the primary welding piece on the welding area of ​​the frame, then place the chip on the primary welding piece, and then place the secondary welding piece, small welding piece and connecting piece on the chip in sequence. Put the graphite jig loaded with components into the vacuum welding furnace to complete the primary welding.

[0077] Secondary welding: Before secondary welding, the welding parts should be inspected and prepared in detail to ensure that the welding quality meets the requirements. The initial welding quality inspection uses non-destructive testing to check whether there are defects in the weld, clean up impurities in the initial welding parts, so as to prevent the quality of the secondary welding from being affected, and evaluate the state of the heat-affected zone to avoid overheating or improper cooling that may lead to material performance degradation;

[0078] According to the welding materials, welding structure and use requirements, select the appropriate welding process and equipment, control the welding heat input, and in the secondary welding, select the appropriate welding sequence and welding position according to the shape, structure and position of the welding workpiece, start welding from the low stress area, gradually transition to the high stress area, control the cooling rate of each welding layer to avoid thermal cracks, and then complete the post-weld treatment, and finally pass the quality inspection and acceptance;

[0079] Note: It needs to be further explained that secondary welding refers to welding or repairing the welded parts again after the initial welding to ensure the welding quality or meet specific technical requirements. It is usually carried out when there are defects in the welding or the structure needs to be strengthened.

[0080] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A chip positioning welding method, characterized in that: The following steps are involved: S1, one-time welding; S11, first place the frame on the upper cover of the fixture; S12, loading a primary soldering sheet on the frame soldering area, and then placing a chip on the primary soldering sheet; S13, placing a secondary soldering sheet, a small soldering sheet and a connecting sheet on the chip in sequence; S14, placing the graphite fixture filled with components into a vacuum welding furnace to complete a welding process; S2, secondary welding; S21. Preparation and implementation of secondary welding: Before secondary welding, the welding parts should be inspected and prepared in detail to ensure that the welding quality meets the requirements. The specific preparation work includes: S211. Initial welding quality inspection: Check whether the weld has defects through non-destructive testing; S212, welding part cleaning: clean the impurities in the initial welding part to prevent affecting the quality of the secondary welding; S213, Welding heat affected zone assessment: Assess the state of the heat affected zone to avoid overheating or improper cooling that may lead to material performance degradation; S214. Select suitable welding process: select suitable welding process and equipment according to welding materials, welding structure and use requirements; S215, controlling welding heat input; S216, controlling the welding sequence and welding position: during the secondary welding, selecting an appropriate welding sequence and welding position according to the shape, structure and position of the welding workpiece; S217, start welding from the low stress area and gradually transition to the high stress area; S218, cooling control: control the cooling rate of each welding layer to avoid thermal cracks; S22, post-weld treatment; S23. Quality inspection and acceptance.

2. A chip positioning welding method according to claim 1, characterized in that: In S13, the small welding piece is used to weld the lead wire and the connecting piece. In S14, after one welding is completed, the frame, the primary welding piece, the chip, the secondary welding piece, the small welding piece and the connecting piece are integrated.

3. A chip positioning welding method according to claim 1, characterized in that: In S211, nondestructive testing includes X-ray testing or ultrasonic testing, and when defects exist, the severity of the defects is evaluated and it is confirmed whether to repair them.

4. A chip positioning welding method according to claim 1, characterized in that: In S212, the impurities cleaned include oil stains, rust or oxide layers, and the cleaning methods adopted are steel brushes, grinding wheels, mechanical grinding or chemical cleaning.

5. A chip positioning welding method according to claim 1, characterized in that: In S213, the heat input of the secondary welding should be properly controlled to avoid secondary damage to the original welding quality.

6. A chip positioning welding method according to claim 1, characterized in that: In S215, during the secondary welding process, the heat input needs to be properly controlled. Excessive heat input will result in an excessively large heat-affected zone of the weld joint, thus affecting the mechanical properties of the material; Among them, the measures for controlling welding heat input include adjusting welding current, welding voltage or welding speed parameters.

7. A chip positioning welding method according to claim 1, characterized in that: In S22, post-weld processing is used to eliminate stress generated during the welding process and improve welding quality.

8. A chip positioning welding method according to claim 1, characterized in that: In S23, quality inspection and acceptance are used to ensure that the welding quality meets the design requirements.

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