Welding method of chip ceramic dielectric capacitor microstrip product

Abstract

The invention discloses a welding method for a chip ceramic dielectric capacitor microstrip product, and belongs to the technical field of electronic component welding processes. According to the technical scheme, the method comprises the following steps of: 1, coating a first layer of soldering paste on the top surfaces of two metal ends of the chip ceramic dielectric capacitor; 2, placing a silver sheet on the first layer of soldering paste, wherein the size of the silver sheet is matched with that of the metal end; step 3, coating a second layer of soldering paste on the surface of the silver sheet; fourthly, the welding face of the L-shaped silver strip or the silver-plated copper strip is attached to the silver piece coated with the second layer of soldering paste; (5) the attached assembly is fixed in a mold; and 6, reflow soldering is carried out. The method has the beneficial effects that the welding adhesive force and the appearance of the chip ceramic dielectric capacitor microstrip product are synchronously optimized, and the qualified rate of the product is improved.

Description

Technical Field

[0001] The invention relates to a welding method for a chip-type ceramic capacitor microstrip product, belonging to the technical field of electronic component welding technology. Background Art

[0002] Microstrip ceramic capacitors are widely used in radio frequency circuits, microwave communications, and high-frequency electronic devices. Their core structure consists of a ceramic capacitor (such as an MLCC) welded to an L-shaped silver ribbon (or silver-plated copper ribbon). These products must meet the stability requirements of high-frequency signal transmission and have strict standards for solder joint appearance quality (such as flatness and absence of warpage) and solder adhesion strength (mechanical strength).

[0003] 1. Existing welding technology and core contradictions

[0004] The current mainstream welding process is reflow soldering combined with mold fixing method, such as Figure 1 The specific steps are as follows:

[0005] Solder paste coating: evenly apply the solder paste on the top surface of the capacitor metal terminal;

[0006] Silver ribbon lamination: Lay the welding surface of the L-shaped silver ribbon (or silver-plated copper ribbon) on the paste-coated end;

[0007] Mold fixing: The components are placed in a special mold and fixed with pressure to prevent displacement;

[0008] Reflow soldering: The solder is melted in a high-temperature reflow oven to achieve direct soldering of the silver ribbon and the capacitor terminal through solder paste.

[0009] However, the amount of solder paste applied becomes the core factor restricting quality:

[0010] Too little solder paste (e.g., less than 80% of the end area): The solder cannot fully fill the interface gap, resulting in voids or unfused areas in the solder joints, and the appearance inspection fails. The effective bonding area is reduced, and the welding adhesion tension is significantly reduced, which cannot meet the requirements of high-reliability scenarios (such as automotive radar and aerospace equipment).

[0011] Excessive solder paste (e.g., exceeding the edge of the terminal by more than 0.1 mm): After melting, the solder overflows, contaminating the capacitor ceramic or microstrip line, causing appearance defects and high-frequency signal interference (overflow forms parasitic capacitance). Although adhesion is improved, the appearance failure rate is greater than 30%, and overflow may cause the silver ribbon to warp, triggering abnormal electromagnetic wave emission from the RF circuit.

[0012] 2. Technical bottlenecks and industry pain points

[0013] Irreconcilable contradiction between adhesion and appearance:

[0014] While ensuring the appearance of the solder joints is qualified (no overflow, no voids), the welding adhesion of traditional processes can usually only reach the lower limit of customer standards, which is difficult to meet the requirements of high-end customers (such as adhesion needs to be increased to more than 150% of the baseline value).

[0015] Limitations of destructive testing:

[0016] Adhesion tensile strength must be verified through destructive sampling tests, and the batch pass rate relies on statistical sampling. If all samples pass, the entire batch is considered passed, but there is actually a risk of hidden failure, and full inspection is not possible.

[0017] 3. Limitations of relevant patented technologies

[0018] Microstrip capacitor soldering die (patent application number: 2004100854785): Spring pressure is used to offset solder surface tension, but the problem of precise control of solder paste volume is not solved, and the adhesion improvement is limited (only 20-30%).

[0019] Manufacturing process for chip ceramic capacitors (Patent Publication No. CN1635594A): Pi-shaped lead bending improves production efficiency, but does not optimize the solder joint microstructure, and adhesion is still limited by the interfacial strength of a single layer of solder paste.

[0020] An automatic assembly and welding linkage machine for chip ceramic capacitors (patent application number: 2008100446002): It realizes the automation of preheating, tinning, and placement, but the amount of solder paste still relies on manual setting, and has not broken through the "quantity control-strength-appearance" triangle contradiction. Summary of the Invention

[0021] In order to solve the defects of the prior art, the purpose of the present invention is to provide a welding method for chip ceramic capacitor microstrip products, which solves the technical problem of the mutual restriction between welding appearance quality and welding adhesion.

[0022] The technical solution of the present invention is: a method for welding a chip ceramic capacitor microstrip product, comprising the following steps:

[0023] Step 1: Apply the first layer of solder paste on the top surface of the two metal ends of the chip ceramic capacitor;

[0024] Step 2: Place a silver sheet on the first layer of solder paste, the size of the silver sheet matching the metal end;

[0025] Step 3: Apply a second layer of solder paste on the surface of the silver sheet;

[0026] Step 4: Lay the soldering surface of the L-shaped silver ribbon or silver-plated copper ribbon on the silver sheet coated with the second layer of solder paste;

[0027] Step 5: Fix the bonded components in the mold;

[0028] Step 6: Perform reflow soldering to weld the L-shaped silver strip or silver-plated copper strip to the metal end of the capacitor through the silver sheet and solder paste to form an integrated structure.

[0029] The thickness of the silver sheet is 0.1 mm ± 0.02 mm.

[0030] The area of ​​the silver sheet is less than 80% to 85% of the area of ​​the top surface of the metal end of the capacitor, and the silver sheet is placed in the center of the metal end.

[0031] The peak temperature of the reflow soldering is 285° C.±5° C., the holding time is 60-120 seconds, and the heating rate is ≤3° C. / second.

[0032] The mold is a spring-loaded structure, which applies pressure to the silver ribbon during the welding process to fix the assembled components.

[0033] The beneficial effects of the present invention are: through the welding method of the present application, the simultaneous optimization of the welding adhesion and appearance of the chip ceramic dielectric capacitor microstrip product is achieved: the silver sheet expands the solder contact area, and the secondary solder paste fills the interface microgap, thereby improving the welding adhesion; the solder is constrained within the boundary of the silver sheet, thereby improving the appearance qualification rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a schematic diagram of the soldering method of traditional chip ceramic capacitor microstrip products;

[0035] Figure 2 This is a schematic diagram of the welding method of this application. DETAILED DESCRIPTION

[0036] The following is combined with Figure 2 The present invention will be further described:

[0037] Example 1

[0038] 1. First layer of solder paste coating:

[0039] Use a precision dispensing machine (needle inner diameter 0.2mm) to apply solder paste on the top surface of the two metal terminals of the capacitor, with a coverage rate of ≥95% of the terminal area.

[0040] 2.Silver sheet lamination:

[0041] Place the silver sheet (0.1mm thickness) precisely on the solder paste layer, aligning the edge with the end according to the center point (position deviation ≤ 0.05mm), and the area of ​​the silver sheet ≥ 80% of the top surface area of ​​the capacitor metal end.

[0042] 3. Second layer of solder paste coating:

[0043] Apply solder paste a second time on the surface of the silver sheet, covering the entire surface of the silver sheet and extending to the edge by about 0.2mm to form a double solder paste layer structure.

[0044] 4. L-shaped silver belt assembly:

[0045] Lay the welding surface of the L-shaped silver ribbon (made of Ag99.9% or silver-plated copper ribbon) on the paste-coated silver sheet.

[0046] 5. Mold fixing and pressurization:

[0047] The component is placed in the mold positioning groove, and after the mold is closed, the spring applies pressure to fix it, suppressing the warping of the silver ribbon caused by the surface tension of the solder.

[0048] 6. Reflow soldering:

[0049] The reflow soldering furnace is filled with nitrogen to keep the oxygen concentration in the furnace below 50ppm. After the solder melts, a silver sheet-end-silver ribbon sandwich structure is formed with no voids at the interface.

[0050] Example 2

[0051] Adhesion test:

[0052] The welding adhesion was measured using a tensile testing machine (brand: Pusanda, model: BY-128X).

[0053] For components using the commonly used 2225 package, the welding adhesion is about 22.5-27.5N under the traditional single-layer solder paste welding process. However, using the welding process of Example 1, the adhesion of the 2225 size reaches 31.7-37.5N, which is an improvement of more than 40%. The welding adhesion of other product sizes is also improved by 38%-46%. The fracture position is located at the silver ribbon body rather than the solder point, proving that the interface bonding strength is greater than the silver ribbon material strength.

[0054] Example 3

[0055] Appearance and reliability:

[0056] X-ray inspection (resolution 2μm) showed that the void ratio of the solder joint was less than 0.1% and there was no overflow.

[0057] Temperature cycle test, temperature -55℃~125℃, no cracking after 1000 cycles.

[0058] When welding using the method of this application, the adhesion and appearance of the solder joints meet the standards.

[0059] 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 welding a chip ceramic capacitor microstrip product, characterized in that: The steps include: Step 1: Apply the first layer of solder paste on the top surface of the two metal ends of the chip ceramic capacitor; Step 2: Place a silver sheet on the first layer of solder paste, the size of the silver sheet matching the metal end; Step 3: Apply a second layer of solder paste on the surface of the silver sheet; Step 4: Lay the soldering surface of the L-shaped silver ribbon or silver-plated copper ribbon on the silver sheet coated with the second layer of solder paste; Step 5: Fix the bonded components in the mold; Step 6: Perform reflow soldering to weld the L-shaped silver strip or silver-plated copper strip to the metal end of the capacitor through the silver sheet and solder paste to form an integrated structure.

2. The method for soldering a microstrip chip ceramic capacitor according to claim 1, wherein: The thickness of the silver sheet is 0.1 mm ± 0.02 mm.

3. The welding method of a chip ceramic capacitor microstrip product according to claim 1, characterized in that: The area of ​​the silver sheet is 80% to 85% of the area of ​​the top surface of the metal end of the capacitor, and the silver sheet is placed in the center of the metal end.

4. The method for soldering a microstrip chip ceramic capacitor according to claim 1, wherein: The peak temperature of the reflow soldering is 285° C.±5° C., the holding time is 60-120 seconds, and the heating rate is ≤3° C. / second.

5. The welding method of a chip ceramic capacitor microstrip product according to claim 1, characterized in that: The mold is a spring-loaded structure that applies pressure to the silver ribbon before welding to fix the assembled components.

Images