High-stability welding structure
By setting a stress release layer under the silver pad to buffer the welding stress, the problem of pad stress concentration is solved, and the welding strength and product reliability are improved.
Patent Information
- Application Number
- CN202422553159.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-22
- Publication Date
- 2025-08-29
- Estimated Expiration
- 2034-10-22
AI Technical Summary
During the welding process, the intermetallic compound Ag3Sn is brittle and hard, resulting in the pad stress concentration, which easily leads to the separation of the pad from the substrate, affecting the solder strength and product reliability.
A stress relief layer is set under the silver pad, and a gold layer or a platinum layer is used to buffer the stress during the welding process, release stress, and improve welding strength.
Through the design of the stress relief layer, the welding strength is significantly improved, the risk of pad falloff is reduced, and the product quality is improved.
Smart Images
Figure CN223284986U_ABST
Abstract
Description
Technical field:
[0001] The utility model relates to the technical field of microelectronic packaging, in particular to a high-stability welding structure which can significantly improve the welding strength of welding points and thus enhance product quality. Background technology:
[0002] In the manufacturing of electronic products, solder joints not only enable electrical connections between electronic components, facilitating signal transmission and circuit continuity, but also provide mechanical support. Solder joints are the weakest link in electronic assemblies and a crucial component of electronic devices. Solder failures often account for 70% of all electronic product failures. Tin-lead solders play a crucial role in the electronics industry, with eutectic tin-lead alloy (melting point 183°C)-based solders (Sn-Pb type) widely used due to their low cost and excellent performance. Currently, lead-containing solders are still permitted in certain specialized applications, but they pose significant risks, severely impacting the ecological environment and human health, and are destined for elimination in the electronics packaging industry. The European Union proposed a ban on the use of lead-containing materials in 2003 and officially implemented lead-free solders in 2006.
[0003] Tin-based solders are widely used in electronic device interconnection technology due to their low cost, excellent mechanical properties, and high stability. The Sn atoms in tin-based solders often react with metal atoms such as Au, Ni, Ag, and Cu to form intermetallic compounds, resulting in excellent wettability and solderability. Therefore, it is considered one of the most important elements in replacing Pb-Sn solders. However, these materials often have imperfect performance. In some cases, poor wettability presents significant limitations for tin-based solders.
[0004] In semiconductor welding technology, silver pads and tin paste are commonly used for electrical conductivity and low cost. However, at high temperatures, silver and tin will penetrate each other to form metal compounds. At high temperatures, they will continue to penetrate each other, such as Ag3Sn intermetallic compounds. Figure 1 As shown, the volume and hardness of this compound are significantly different from those of tin and silver. Stress can cause problems such as pad peeling, which in turn leads to connection failure. Summary of the invention:
[0005] In view of the shortcomings and deficiencies in the prior art, the utility model proposes a high-strength welding pad device which can significantly improve the welding strength of the welding spot and thus improve the product quality.
[0006] The utility model is achieved through the following measures:
[0007] A high-stability welding structure is provided with a silver pad located on the surface of a substrate. It is characterized in that a stress release layer for releasing stress is also provided under the silver pad. The stress release layer adopts a metal layer with good ductility, and the area of the stress release layer does not exceed the area of the silver pad.
[0008] The stress release layer of the present invention adopts a gold layer or a platinum Pt layer, so as to utilize the good ductility of the gold layer or the platinum layer to release the stress caused by the hard compound during the welding process of the silver pad.
[0009] The thickness of the silver pad of the present invention is in the range of 6-20 μm, the thickness of the stress release layer is in the range of 0.2-0.7 μm, and the silver pad completely covers the stress release layer; further, the thickness of the silver pad is preferably 8-15 μm, and the thickness of the stress release layer is preferably 0.3 μm-0.4 μm to meet the processing requirements of microelectronic products.
[0010] The stress release layer described in the present invention is an integral structure or a discontinuous structure composed of two or more stress release units. When the stress release layer adopts an integral structure, the stress release layer is a complete metal sheet layer, which can be circular, triangular, rectangular, or elliptical; when the stress release layer adopts a discontinuous structure, it can adopt an array composed of two or more strips arranged at equal intervals, or it can adopt an array composed of two or more circles arranged at equal intervals. The width range of the silver pad is 250-700μm, and the length range of the silver pad is 1100-1500μm. The spacing range between two adjacent stress release units in the stress release layer with a discontinuous structure is 1-50μm. The stress release layer with a discontinuous structure can further increase the stress release space, thereby improving the welding quality.
[0011] The substrate of the present invention is an insulating substrate, which may be a glass substrate or a ceramic substrate.
[0012] The present utility model can be applied to a thermal print head product, wherein the thermal print head is provided with a heating substrate for the thermal print head: comprising an insulating substrate, an electrode wire layer being arranged on the insulating substrate, the electrode wire layer being composed of electrode wires, the electrode wires comprising a bonding electrode pattern, the electrode wire layer being connected to a heating resistor layer at a position corresponding to the heat storage glaze coating to form a heating resistor for generating Joule heat, and the position where the insulating substrate is welded to the external cable being provided with the silver pad as described above; in this application scenario, the material of the electrode wire layer is aluminum, silver, gold, copper or an alloy thereof, and the electrode wire is obtained by printing, sintering or magnetron sputtering; the heating resistor layer is composed of tantalum or ruthenium and its oxides, and is obtained by printing, sintering or magnetron sputtering.
[0013] The utility model adopts a novel silver pad structure and utilizes a stress release layer (gold layer or platinum layer) at the bottom of the silver pad to buffer and release the stress during the welding process, thereby increasing the strength of the solder joint; the stress during the welding process comes from the mutual diffusion of tin and silver to form an intermetallic compound Ag3Sn during the welding process, which is brittle and hard, resulting in a large downward internal stress in the pad, making the pad very fragile, and easily causing the silver pad to fall off from the substrate, resulting in welding failure; compared with the existing technology, the utility model can effectively improve the welding strength between the substrate and the cable, avoid peeling at the connection, and is suitable for application in the microelectronics packaging industry. Description of the drawings:
[0014] Attachment Figure 1 This is a microscopic diagram of the diffusion of two materials to produce a hard compound during the silver pad welding process.
[0015] Attachment Figure 2 This is a schematic diagram of the silver pad structure in Example 1 of the present utility model, wherein Figure 2 Figure a is a front view of the silver pad structure in Example 1. Figure 2 Figure b is a side view of the silver pad structure in Example 1.
[0016] Attachment Figure 3 This is a schematic diagram of the silver pad structure in Example 2 of the present utility model, wherein Figure 3 Figure a is a front view of the silver pad structure in Example 2. Figure 3 Figure b is a side view of the silver pad structure in Example 2.
[0017] Attachment Figure 4 This is a schematic diagram of the silver pad structure in Example 3 of the present utility model.
[0018] Attachment Figure 5 This is a schematic diagram of the second structure of the silver pad in Example 1 of the present utility model.
[0019] Reference numerals: silver pad 1 , stress release layer 2 , substrate 3 . Specific implementation method:
[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments.
[0021] Example 1:
[0022] This example provides a high-strength solder pad, as shown in the attached Figure 2 , Attachment Figure 5As shown, in this example, a silver pad 1 is provided on a substrate 3, and a stress release layer 2 for releasing stress is provided below the silver pad 1. The stress release layer 2 in this example adopts a gold layer with good ductility. The stress release layer 2 in this example adopts an integral gold sheet layer, and its area is smaller than that of the silver pad 1. The bottom surface of the gold layer is in contact with the substrate 3, and the remaining surface of the gold layer is in contact with the bottom surface of the silver pad 1.
[0023] In this example, the substrate 3 is an insulating ceramic substrate whose main component is Al2O3, and the thickness of the gold layer is 0.3 μm. The gold layer is located in the central area of the silver pad 1, and the silver pad 1 is made by printing and sintering technology;
[0024] Experimental tests have shown that when a gold layer is placed beneath the silver pad, due to its low hardness, gold has a certain degree of deformation ability, which can release the stress transmitted from the pad, thereby reducing damage to the pad and achieving the purpose of improving welding strength. Microelectronic products using the silver pad structure in this example, such as the cable connection part of the thermal print head, have significantly improved cable connection strength and tensile strength, reducing the product defective rate caused by pad peeling and loose solder joints.
[0025] Example 2:
[0026] As attached Figure 3 As shown, this example proposes a high-strength pad structure. In this example, a silver pad 1 is provided on a substrate 3. A discontinuous stress release layer 2 is provided at the bottom of the silver pad 1. In this example, the stress release layer 2 is still made of a gold layer with a thickness of 0.3 μm. Unlike Example 1, the stress release layer 2 is provided with two or more equally spaced strip-shaped stress release units. The spacing between the strip-shaped stress release units is 1.0-20 μm and is obtained by etching.
[0027] Experimental tests show that the silver pad structure of this example can achieve a welding strength similar to that of Example 1 while effectively reducing the consumption of the gold layer.
[0028] Example 3:
[0029] This example provides a high-strength pad structure, as shown in the attached Figure 4 As shown, in this example, a silver pad 1 is provided on a substrate 3, and a stress release layer 2 with a discontinuous structure is provided at the bottom of the silver pad 1. In this example, the stress release layer 2 with a discontinuous structure is composed of three circular stress release units. The center points of adjacent circular stress release units are connected to form an equilateral triangle. The equilateral triangle can be concentrically arranged with the silver pad 1. The stress release unit uses a gold layer with a thickness of 0.3 μm. The spacing between the stress release units is 2.0-30 μm and is obtained by etching.
[0030] Experimental tests have shown that the silver pad structure of this example can effectively reduce the consumption of the gold layer while effectively improving the welding strength of the product.
[0031] The utility model adopts a novel silver pad structure and utilizes a stress release layer (gold layer or platinum layer) at the bottom of the silver pad to buffer and release the stress during the welding process, thereby increasing the strength of the solder joint; the stress during the welding process comes from the mutual diffusion of tin and silver to form an intermetallic compound Ag3Sn during the welding process, which is brittle and hard, resulting in a large downward internal stress in the pad, making the pad very fragile, and easily causing the silver pad to fall off from the substrate, resulting in welding failure; compared with the existing technology, the utility model can effectively improve the welding strength between the substrate and the cable, avoid peeling at the connection, and is suitable for application in the microelectronics packaging industry.
Claims
1. A high stability soldering structure having a silver soldering pad located on the surface of a substrate, characterized in that: A stress release layer for releasing stress is also provided under the silver pad. The stress release layer is made of a metal layer with good ductility, and the area of the stress release layer does not exceed the area of the silver pad.
2. The high stability welding structure according to claim 1, characterized in that: The stress release layer is a gold layer or a platinum Pt layer.
3. The high stability welding structure according to claim 2, characterized in that: The thickness of the silver pad is in the range of 6-20 μm, the thickness of the stress release layer is in the range of 0.2-0.7 μm, and the silver pad completely covers the stress release layer.
4. The high stability welding structure according to claim 3, characterized in that: The thickness of the silver pad is 8-15 μm, and the thickness of the stress release layer is correspondingly 0.3 μm-0.4 μm.
5. The high stability welding structure according to claim 1, characterized in that: The stress release layer is an integral structure or a discontinuous structure composed of two or more stress release units. When the stress release layer adopts an integral structure, the stress release layer is a complete metal sheet layer.
6. The high stability welding structure according to claim 5, characterized in that: When the stress release layer adopts a discontinuous structure, an array consisting of two or more strips arranged at equal intervals, or an array consisting of two or more circles arranged at equal intervals, the width range of the silver pad is 250-700 μm, the length range of the silver pad is 1100-1500 μm, and the spacing range between two adjacent stress release units in the stress release layer with a discontinuous structure is 1-50 μm.
7. The high stability welding structure according to claim 1, characterized in that: The substrate is an insulating substrate, a glass substrate or a ceramic substrate.