Sn whisker suppression method for electronic packaging
By adding barrier phase or absorbing phase materials to Sn or Sn alloys, the long-distance diffusion of active Sn atoms is hindered, and composite materials are prepared to inhibit the growth of Sn whiskers, which solves the circuit short circuit and equipment failure problems caused by Sn whiskers, and improves the reliability and safety of electronic packaging.
Patent Information
- Application Number
- CN202510446937.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-10
- Publication Date
- 2025-07-11
AI Technical Summary
The prior art is difficult to effectively suppress the growth of Sn whiskers, resulting in circuit short circuits, equipment failures and signal interference, especially in lead-free electronic packaging, risk intensified.
By adding barrier phase or absorbing phase materials to Sn or Sn alloys, the long-distance diffusion or absorption of active Sn atoms are blocked, and the composite material is prepared by a temperature-pressure process to limit the growth of Sn whiskers.
It significantly inhibits the growth of Sn whiskers, improves the reliability and safety of electronic packaging, and is simple to operate and low cost.
Smart Images
Figure CN120291205A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical fields of metal matrix composites and Sn whisker inhibition, and can be widely applied to fields such as Sn-based solders and electronic packaging. Background Art
[0002] The spontaneous growth of Sn whiskers is the formation of slender filaments on the surface of Sn materials under specific environmental conditions. These Sn whiskers often appear on the Sn coatings and solder surfaces of electronic packaging systems, causing problems such as short circuits, equipment failures, and signal interference. The industry is no stranger to the phenomenon of Sn whisker growth. However, due to its high randomness (the incubation period ranges from a few minutes to more than a decade), the experimental repeatability is extremely poor, making research work extremely difficult. In fact, the electronics industry has suffered from whiskers since its inception, and related accidents have emerged in an endless stream. In the 1960s, Arnold et al. found that Pb can inhibit the growth of Sn whiskers, and SnPb alloys became the "good prescription" in the industry. However, the neurotoxicity of Pb forced the industry to turn to "lead-free". Therefore, the problem of Sn whiskers, which was once suppressed by Pb, has made a comeback. Since the silicon crystal manufacturing process is approaching the lower limit, 3D packaging has become an important development direction. The technical difficulties of 3D packaging technology and problems such as product yield mainly involve bonding processes and materials. The increase in interconnect density further exacerbates the risk of Sn whiskers. Nowadays, intelligent vehicles have integrated a large number of electronic devices, and their reliability is related to the safety of drivers and passengers. It can be said that the problem of Sn whiskers is related to the main economic battlefield and people's lives and health.
[0003] Currently, there have been various methods tried to inhibit the growth of Sn whiskers, such as introducing surface conformal coating technology or optimizing the matrix material by alloying technology, etc. However, the effects of these methods are all limited. Therefore, how to restrict the generation of Sn whiskers at the atomic level has become the core issue in the research of Sn whisker inhibition. Summary of the Invention
[0004] Technical Problem: The purpose of the present invention is to provide a method for inhibiting Sn whiskers in electronic packaging, a reliable method for inhibiting Sn whiskers based on the active Sn atom mechanism, to solve the problem of Sn whisker growth in Sn or Sn alloys. By adding a barrier phase material that can hinder the long-distance diffusion of active Sn atoms or an absorption phase that can absorb active Sn atoms, the effect of significantly inhibiting whisker growth can be achieved.
[0005] Technical Solution: The core technology of the present invention is to add a barrier phase that can hinder the long-distance diffusion of active Sn atoms or an absorption phase that can absorb active Sn atoms, and achieve its metallurgical bonding with Sn or Sn alloys under temperature and pressure to achieve the effect of inhibiting Sn whisker growth. This method is based on the role of active Sn atoms in the growth of Sn whiskers and is achieved through the following steps:
[0006] Step 1. Mix Sn or Sn alloy powder with a barrier phase or an absorption phase capable of absorbing active Sn atoms in a set ratio to form a mixture. The comparative sample is the corresponding metal matrix without adding the barrier phase or absorption phase.
[0007] Step 2. Prepare a composite material from the mixture in Step 1 through warm compaction process. Utilize the barrier effect of the barrier phase or absorb active Sn atoms to restrict the long-distance diffusion of active Sn atoms, thereby achieving the effect of inhibiting the growth of Sn whiskers.
[0008] Step 3. Cultivate the composite material prepared by the warm compaction process in Step 2 under variable temperature or constant temperature, high humidity conditions and set atmosphere conditions to accelerate whisker growth, so as to facilitate the observation of whisker growth phenomenon. Compare and observe the inhibitory effect of Sn whisker growth under SEM.
[0009] The barrier phase is graphene, MXene, molybdenum disulfide or other materials with barrier ability.
[0010] The absorption phase capable of absorbing active Sn atoms is a material that can confine active atoms within a local range.
[0011] The absorption phase includes activated carbon or silica aerogel.
[0012] The addition amount ratio of the barrier phase or absorption phase to Sn or Sn alloy is 1:10000 - 1:20 in terms of molar ratio.
[0013] The temperature range for preparing the composite material through the warm compaction process is 100 - 230 °C, the pressure range is 100 - 300 MPa, and the pressure holding time is 5 - 60 minutes to ensure that the added barrier phase or absorption phase can form a metallurgical bond with Sn or Sn alloy.
[0014] The atmosphere for accelerating whisker growth is air, argon or nitrogen, the temperature is 20 - 210 °C, the relative humidity is 50% - 100%, and the time is 12 h - 48 h.
[0015] For comparing and observing the inhibitory effect of Sn whisker growth, verify the whisker growth situation, the barrier effect of the added barrier phase or the adsorption effect of the absorption phase through characterization techniques such as X-ray diffraction (XRD), gas chromatography (GC), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and transmission electron microscopy (TEM).
[0016] The set ratio is as follows: The Sn or Sn alloy and the barrier phase or absorption phase are mixed evenly in a molar ratio of 1:0.0001 - 1:0.0500.
[0017] The Sn or Sn alloy mentioned above includes binary or ternary Sn alloys such as pure Sn, SnBi, SnPb, SnZn, SnAg, and SnAgCu.
[0018] Principle of the invention: Active Sn atoms are the direct cause of Sn whisker growth. From the perspective of the diffusion of active Sn atoms, by adding a barrier phase (including graphene, MXene, molybdenum disulfide, etc.) that can hinder the long-distance diffusion of active Sn atoms or an absorption phase (including activated carbon and silica aerogel, etc.) that can absorb active Sn atoms, the diffusion and aggregation nucleation can be prevented, thereby achieving the effect of inhibiting whisker growth. In this invention, by adding a barrier phase to hinder the long-distance diffusion of active Sn atoms or an absorption phase to adsorb active Sn atoms in the Sn and its alloy matrix, the migration and aggregation can be prevented, so as to inhibit the growth of Sn whiskers. By cultivating under constant temperature or variable temperature, high humidity, and certain atmosphere conditions to accelerate whisker growth, the inhibition effect can be observed and compared.
[0019] Beneficial effects: Compared with the prior art, the remarkable effect achieved by this invention is that by adding a barrier phase material that can hinder the long-distance diffusion of active Sn atoms or an absorption phase that can absorb active Sn atoms, the effect of significantly inhibiting whisker growth can be achieved; this invention has the advantages of simple operation, high efficiency, and low cost. Description of the drawings
[0020] Figure 1 It is a schematic diagram of the Sn whisker inhibition method;
[0021] Figure 2 It is a diagram of the whisker growth situation after culturing in a constant temperature and humidity chamber at 30°C for 5 days in Example 1 of the present invention;
[0022] Figure 3 It is a diagram of the whisker growth situation after culturing in a constant temperature and humidity chamber at 30°C for 5 days in Example 2 of the present invention;
[0023] Figure 4 It is a diagram of the whisker growth situation after culturing in a constant temperature and humidity chamber at 30°C for 5 days in Example 3 of the present invention;
[0024] Figure 5 It is a diagram of the whisker growth situation after culturing in a constant temperature and humidity chamber at 30°C for 5 days in Example 4 of the present invention;
[0025] Figure 6 It is a diagram of the whisker growth situation after culturing in a constant temperature and humidity chamber at 30°C for 5 days in Example 5 of the present invention;
[0026] Figure 7 It is a diagram of the whisker growth situation after culturing in a constant temperature and humidity chamber at 30°C for 5 days in Example 6 of the present invention;
[0027] Figure 8This is the diagram of whisker growth after the 6th embodiment of the present invention was cultured in a constant temperature and humidity chamber at 30°C for 5 days. Detailed implementation manners
[0028] The present invention will be further described in detail below.
[0029] Step 1. Mix Sn or Sn alloy powder with a barrier phase or an absorption phase capable of absorbing active Sn atoms in a set ratio to form a uniform mixture. The comparative sample is the corresponding metal matrix without adding a barrier phase or an absorption phase.
[0030] Step 2. Prepare a composite material from the mixture in Step 1 through warm compaction technology. Utilize the barrier effect of the barrier phase or absorb active Sn atoms to limit the long-distance diffusion of active Sn atoms, thereby achieving the effect of inhibiting the growth of Sn whiskers.
[0031] Step 3. Culture the composite material prepared by warm compaction technology in Step 2 under variable temperature or constant temperature, high humidity conditions, and set atmosphere conditions to accelerate whisker growth, so as to facilitate the observation of whisker growth phenomena, and compare and observe the inhibitory effect of Sn whisker growth under SEM.
[0032] Example 1
[0033] In this example, a set mass of metallic Sn powder is metallurgically bonded through warm compaction, and the sample is cultured under constant temperature, high humidity, and set atmosphere conditions to observe the whisker growth state. The specific steps are as follows:
[0034] (1) Weigh 2 g of metallic Sn powder.
[0035] (2) Keep the pressure of the metallic Sn powder at 220°C and 100 MPa for 30 min, and warm-compact it into a disc-shaped sample with a diameter of 15 mm.
[0036] (3) Culture the sample for 5 days under the conditions of 30°C, 80% relative humidity, and air atmosphere, and observe the whisker growth situation under SEM.
[0037] Example 2
[0038] In this example, a set mass of metallic Sn powder and the barrier phase graphene are uniformly mixed in a three-dimensional powder mixer in a molar ratio of 1:0.01, and the sample is cultured under constant temperature, high humidity, and set atmosphere conditions to observe the whisker growth state. The specific steps are as follows:
[0039] (1) Weigh 2 g of metallic Sn powder.
[0040] (2) Uniformly mix the metallic Sn powder and the barrier phase graphene in a three-dimensional powder mixer for 1 h in a molar ratio of 1:0.01.
[0041] (3) Keep the mixed powder under pressure for 30 min at 220 °C and 100 MPa, and warm-press it into a disk sample with a diameter of 15 mm;
[0042] (4) Cultivate the sample for 5 days at 30 °C, 80% relative humidity, and in an air atmosphere, and observe the whisker growth by SEM.
[0043] Example 3
[0044] In this example, a set mass of metallic Sn powder and the barrier phase MXene are uniformly mixed in a three-dimensional powder mixer at a molar ratio of 1:0.01, and the sample is cultivated under constant temperature, high humidity, and a set atmosphere condition to observe the whisker growth state. The specific steps are as follows
[0045] (1) Weigh 2 g of metallic Sn powder;
[0046] (2) Uniformly mix the metallic Sn powder and the barrier phase MXene in a three-dimensional powder mixer at a molar ratio of 1:0.01 for 1 h;
[0047] (3) Keep the mixed powder under pressure for 30 min at 220 °C and 100 MPa, and warm-press it into a disk sample with a diameter of 15 mm;
[0048] (4) Cultivate the sample for 5 days at 30 °C, 80% relative humidity, and in an air atmosphere, and observe the whisker growth by SEM.
[0049] Example 4
[0050] In this example, a set mass of metallic Sn powder and the barrier phase MXene are uniformly mixed in a three-dimensional powder mixer at a molar ratio of 1:0.003, and the sample is cultivated under constant temperature, high humidity, and a set atmosphere condition to observe the whisker growth state. The specific steps are as follows
[0051] (1) Weigh 2 g of metallic Sn powder;
[0052] (2) Uniformly mix the metallic Sn powder and the barrier phase MXene in a three-dimensional powder mixer at a molar ratio of 1:0.003 for 1 h;
[0053] (3) Keep the mixed powder under pressure for 30 min at 220 °C and 100 MPa, and warm-press it into a disk sample with a diameter of 15 mm;
[0054] (4) Cultivate the sample for 5 days at 30 °C, 80% relative humidity, and in an air atmosphere, and observe the whisker growth by SEM.
[0055] Example 5
[0056] In this embodiment, metal Sn powder of a set quality and barrier-phase activated carbon powder are mixed evenly in a three-dimensional powder mixer according to a molar ratio of 1:0.01, and samples are cultured under constant temperature, high humidity, and set atmosphere conditions to observe the whisker growth state. The specific steps are as follows:
[0057] (1) Weigh 2 g of metal Sn powder;
[0058] (2) Uniformly mix the metal Sn powder and the barrier-phase activated carbon powder in a three-dimensional powder mixer for 1 h according to a molar ratio of 1:0.01;
[0059] (3) Keep the pressure of the mixed powder at 220 °C and 100 MPa for 30 min, and warm-press it into a disk-shaped sample with a diameter of 15 mm;
[0060] (4) Culture the sample for 5 days at 30 °C, 80% relative humidity, and in an air atmosphere, and observe the whisker growth by SEM.
[0061] Example 6
[0062] In this embodiment, SnBi alloy powder of a set quality is metallurgically bonded by warm pressing, and samples are cultured under constant temperature, high humidity, and set atmosphere conditions to observe the whisker growth state. The specific steps are as follows:
[0063] (1) Weigh 2 g of metal SnBi alloy powder;
[0064] (2) Keep the pressure of the SnBi alloy powder at 120 °C and 100 MPa for 30 min, and warm-press it into a disk-shaped sample with a diameter of 15 mm;
[0065] (3) Culture the sample for 5 days at 30 °C, 80% relative humidity, and in an air atmosphere, and observe the whisker growth by SEM.
[0066] Example 7
[0067] In this embodiment, SnBi alloy powder of a set quality and barrier-phase graphene are mixed evenly in a three-dimensional powder mixer according to a molar ratio of 1:0.01, and samples are cultured under constant temperature, high humidity, and set atmosphere conditions to observe the whisker growth state. The specific steps are as follows:
[0068] (1) Weigh 2 g of SnBi alloy powder;
[0069] (2) Uniformly mix the SnBi alloy powder and the barrier-phase graphene in a three-dimensional powder mixer for 1 h according to a molar ratio of 1:0.01;
[0070] (3) Keep the pressure of the mixed powder at 120 °C and 100 MPa for 30 min, and warm-press it into a disk-shaped sample with a diameter of 15 mm;
[0071] (4) The sample was cultured at 30 °C, 80% relative humidity, and in an air atmosphere for 5 days, and the whisker growth was observed by SEM.
[0072] Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 are the diagrams of whisker growth after culturing Examples 1, 2, 3, 4, and 5 at 30 °C and 80% relative humidity for 5 days respectively. It can be seen that Figure 2 in the sample, the whisker growth trend is very strong, the whisker density is high, the number is large, and the length is long. This is because under constant temperature, high humidity, and certain atmosphere conditions, it can promote the generation of active Sn atoms. Under the action of the chemical potential gradient, the active Sn atoms diffuse and aggregate to form nuclei, and Sn whiskers grow rapidly. Figure 3 , Figure 4 In the samples of, due to the addition of two-dimensional barrier materials graphene and MXene that can hinder the long-distance diffusion of active Sn atoms respectively, the long-distance diffusion of active Sn atoms is restricted, preventing their migration and aggregation to form nuclei, thus greatly inhibiting the growth of Sn whiskers. While Figure 5 in the sample of, although it also added the two-dimensional barrier material MXene that can hinder the long-distance diffusion of active Sn atoms, however, due to the insufficient addition amount, although the length and density of the whiskers decreased, it did not achieve the effect of completely inhibiting the whisker growth. Figure 6 In the sample of, due to the addition of the absorption phase activated carbon that can absorb active Sn atoms, the active Sn atoms are restricted within a local range, preventing their migration and aggregation to form nuclei. Therefore, the density, number, and length of the whiskers all decrease.
[0073] Figure 7 , Figure 8 are the diagrams of whisker growth after culturing Examples 6 and 7 at 30 °C and 80% relative humidity for 5 days respectively. It can be seen that under the same temperature, humidity, and atmosphere conditions, Figure 7 the density, number, and length of whisker growth in Figure 2 are different from those in
[0074] Metallurgical bonding of Sn or Sn alloys can be achieved by warm compaction, and whisker growth can be accelerated by culturing under variable temperature or constant temperature, high humidity, and set atmosphere conditions. On this basis, by adding a barrier phase (including graphene, MXene, molybdenum disulfide, etc.) that can hinder the long-distance diffusion of active Sn atoms or an absorption phase (including activated carbon and silica aerogel, etc.) that can absorb active Sn atoms, the migration and subsequent aggregation and nucleation can be prevented, and the formation of Sn whiskers can be inhibited. By warm compaction, the absorption phase or barrier phase is compounded with the Sn or Sn alloy material to simulate the actual use environment. The results show that this method can significantly inhibit the whisker growth on its surface, providing a new solution for the inhibition of Sn whiskers.
[0075] Therefore, the growth of Sn whiskers can be effectively and reliably inhibited by the method of the present invention.
Claims
1. A method for suppressing Sn whiskers in electronic packaging, characterized in that, This method is based on the role of active Sn atoms in the growth of Sn whiskers and is achieved through the following steps: Step 1. Uniformly mix Sn or Sn alloy powder with a barrier phase or an absorption phase capable of absorbing active Sn atoms in a set ratio to form a mixture. The comparative sample is the corresponding metal matrix without adding a barrier phase or an absorption phase. Step 2. Prepare a composite material from the mixture in Step 1 through a warm compaction process. Utilize the barrier effect of the barrier phase or absorb active Sn atoms to restrict the long-distance diffusion of active Sn atoms, thereby achieving the effect of inhibiting the growth of Sn whiskers. Step 3. Cultivate the composite material prepared by the warm compaction process in Step 2 under variable-temperature or constant-temperature, high-humidity conditions and set atmosphere conditions to accelerate whisker growth, so as to facilitate the observation of whisker growth phenomena and compare and observe the inhibitory effect of Sn whisker growth under SEM.
2. The Sn whisker suppression method for electronic packaging according to claim 1, characterized in that The barrier phase is graphene, MXene, molybdenum disulfide or other materials with barrier capabilities.
3. The method for suppressing Sn whiskers in electronic packaging according to claim 1, characterized in that, The absorption phase capable of absorbing active Sn atoms is a material that can confine active atoms within a local range.
4. The Sn whisker suppression method for electronic packaging according to claim 3, characterized in that, The absorption phase includes activated carbon or silica aerogel.
5. The method for suppressing Sn whiskers in electronic packaging according to claim 4, wherein, The addition amount of the barrier phase or absorption phase to Sn or Sn alloy is in a molar ratio of 1:10000 to 1:
20.
6. The method for suppressing Sn whiskers in electronic packaging according to claim 1, characterized in that, The temperature range for preparing the composite material through the warm compaction process is 100 - 230 °C, the pressure range is 100 - 300 MPa, and the pressure holding time is 5 - 60 minutes to ensure that the added barrier phase or absorption phase can form a metallurgical bond with Sn or Sn alloy.
7. The Sn whisker suppression method for electronic packaging according to claim 1, wherein The atmosphere for accelerating whisker growth is air, argon or nitrogen, the temperature is 20 - 210 °C, the relative humidity is 50% - 100%, and the time is 12 h - 48 h.
8. The Sn whisker suppression method for electronic packaging according to claim 1, wherein For the comparative observation of the inhibitory effect of Sn whisker growth, verify the whisker growth situation, the barrier effect of the added barrier phase or the adsorption effect of the absorption phase through characterization techniques such as X-ray diffraction (XRD), gas chromatography (GC), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and transmission electron microscopy (TEM).
9. The Sn whisker suppression method for electronic packaging according to claim 1, wherein The set ratio is as follows: The Sn or Sn alloy and the barrier phase or absorption phase are uniformly mixed in a molar ratio of 1:0.0001 to 1:0.0500.
10. The Sn whisker suppression method for electronic packaging according to claim 1, characterized in that, The Sn or Sn alloy includes binary or ternary Sn alloys such as pure Sn, SnBi, SnPb, SnZn, SnAg, and SnAgCu.