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Packaging and Assembly of Microelectronic Devices and Systems
Published in Anwar Sohail, Raja M Yasin Anwar Akhtar, Raja Qazi Salahuddin, Ilyas Mohammad, Nanotechnology for Telecommunications, 2017
The solder paste print process is used for printing a required volume of solder paste onto the pads of the PCB, using matching apertures on a stencil foil (Figure 14.27). A squeegee is used to drag the paste across the stencil by applying a certain amount of pressure and at a certain speed to enable the print process. The PCB is also adequately supported during the print process to avoid any bowing or flexing and it makes contact with the stencil. The solder paste consists of minute spherical solder particles dispersed in flux. The solder particles are responsible for forming the solder joint and for attaching the component leads or the solder balls onto the pads of the PCB. The flux is responsible for suspending the particles in the paste, protecting the particles from getting oxidized in the paste, cleaning the surface of the pads and the leads before soldering, protecting the leads and pads from oxidation during the soldering process, and forming the flux residue by collecting the byproducts of the cleaning action.
Component Placement and Soldering
Published in Fred W. Kear, Hybrid Assemblies and Multichip Modules, 2020
Solder paste is basically finely divided solder balls suspended in a liquid consisting of flux and other ingredients, the purpose of which is to adjust the viscosity of the paste and to affect its other properties. The functions of the solder paste and the flux are familiar to anyone who has studied conventional soldering processes. These materials have the same function in surface-mount soldering. A more detailed description of the constituents and properties of solder paste was provided earlier in this chapter.
Solder and Automated Soldering Processes
Published in Jack Arabian, Computer Integrated Electronics Manufacturing and Testing, 2020
Solder paste is applied in precise amounts by syringe dispensing or screen/stencil printing before the components are placed. If necessary, adhesive is applied to the substrate after paste application to secure the components. The entire assembly is then heated to reflow the solder.
A flexible and smart shape memory alloy composite sheet based on efficient and bidirectional thermal management
Published in International Journal of Smart and Nano Materials, 2022
Yang Yang, Yongquan Wang, Tao Yao, Xiaojuan Feng
Figure 1(e) shows the steps in the f-TED fabrication. Step 1: TE legs (1.3 mm × 1.3 mm × 1.5 mm) were arranged on a 3D printed mold with row and column spacings of 1.5 mm. Step 2: A rigid substrate with a thermosensitive adhesive was snapped onto the top of the TE legs. The entire device was turned upside-down, and the 3D-printed mold was removed. The transfer of the TE legs to the substrate was, thereby, completed. Step 3: Solder paste (Sn42Bi58 solder paste) was applied to the top of the TE legs. Then, the TE legs were sequentially bridged by 0.06 mm thick copper foils and bonded through a high-temperature re-flow soldering machine. Step 4: A second substrate, coated with a new thermosensitive adhesive, was snapped onto the top of the TE legs bonded with copper foils. Again, the entire device was turned upside-down. The first attached substrate (see step 2) was easily removed as the adhesive strength of the thermosensitive adhesive decreased after high-temperature treatment. Step 5: There was a repetition of step 3. Step 6: Silicone rubber was filled into the gaps of the TE legs. After the silicone rubber was cured, remove the substrates to get the f-TED.
Effects of Sn-Ag-x layers on the solderability and mechanical properties of Sn-58Bi solder
Published in Welding International, 2021
Shuang Zhang, Yang Liu, Hao Zhang, Min Zhou, Yuxiong Xue, Xianghua Zeng, Rongxing Cao, Penghui Chen
The solder materials used in this work were commercial Sn-3.0Ag-0.5Cu (SAC305), Sn-0.3Ag-0.7Cu (SAC0307), Sn-0.3Ag-0.7Cu-0.5Bi-Ni (SACBN), Sn-3.0Ag-3.0Bi-3.0In (SABI333), Sn-58Bi (SnBi) solder pastes. The substrates were Cu pads with an open diameter of 640 μm on the PCB. Firstly, a small amount of the SAC305, SAC0307, SACBN and SABI333 solder pastes were soldered onto the Cu pads, respectively. The parts higher than the solder barrier layer were grinded with sandpaper. Figure 1 shows the structure of the barrier layer formed by SAC305 solder after the above treatment. The structures of the barrier layer of the other three solders, SAC0307, SACBN, and SABI333 are the same as shown in Figure 1, among which the soldering temperature of SAC305, SAC0307, SACBN onto the Cu pads was 260°C. The soldering temperature of SABI333 solder onto the Cu pads was 230°C, and the time was 80s. Secondly, the SnBi solder paste was dispensed onto the barrier layer by the Create-PSD solder paste dispenser. Then, the samples were soldered at 180°C for 80s to form the solder joints. The schematic diagram of manufacturing this structure is shown in Figure 2. For comparison, the pure SnBi/Cu solder joint was also soldered at 180°C for 80s. Here, the height of the five kinds of solder joints was about 610 μm.
Effect of isothermal ageing on the microstructure, shear behaviour and hardness of the Sn58Bi/SnAgCuBiNi/Cu solder joints
Published in Welding International, 2021
Jian Chang, Yang Liu, Hao Zhang, Min Zhou, Xue Yuxiong, Xianghua Zeng, Rongxing Cao, Penghui Chen
The SACBN solder ball and SnBi solder paste were the main solder materials used in this study. The SACBN solder balls were made through cutting and melting processes in glycerol. The SnBi solder paste was a commercial product with eutectic composition. The melting temperature of SACBN and SnBi solder was 220 °C and 139 °C respectively. The customized printed circuit board (PCB) with Cu pads was used as substrate. The diameter of these Cu pads was 640 μm. Firstly, the PCB was cleaned by ethanol under ultrasonic condition for 10 min. Secondly, the SACBN ball with the diameter of 550 μm were positioned onto the Cu pads with flux and then soldered on a heating platform at 260°C for 90s. The AMTECH 4300LF washable flux was used during this soldering process. Then the soldered samples were cooled to room temperature and were cleaned by ethanol to remove residual flux. Finally, the SnBi solder paste was dispensed onto the soldered SACBN joints by the Create-PSD solder paste dispenser. The samples were soldered at 160 °C for 90 s to form the solder joints with superposition structure. The schematic diagram of the fabrication process is presented in Figure 1. For comparison purpose, the SACBN/Cu and SnBi/Cu solder joints with the same geometric size were made at 260°C and 160°C for 90 s respectively. Here the height of all the three kinds of solder joints is 790 μm.