Technical Library | 2017-03-22 20:58:08.0
Water soluble lead-free solder paste is widely used in today’s SMT processes, but the industry is slowly moving away from water soluble solder pastes in favor of no-clean solder pastes. This shift in usage of solder paste is driven by an effort to eliminate the water wash process. Some components cannot tolerate water wash and elimination of water washing streamlines the SMT process. Despite this shift, certain applications lend themselves to the use of water soluble solder paste.This paper details the research and development of a new water soluble lead-free solder paste which improves on the performance characteristics of existing technologies.
Technical Library | 1999-04-15 06:56:07.0
Solder paste is a seemingly simple material that forms one of the foundations of the surface mount assembly operation. If the solder paste does not do its job correctly then first pass yield will be severely reduced.
Technical Library | 2007-01-31 14:14:56.0
This paper explains the solder paste reflow process and the best practices to follow when developing your profile.
Technical Library | 2018-03-15 07:23:35.0
The SMT assembly process is continuously challenged by the factors which enhance circuit board performance and limit productivity. The pick and place and reflow systems reflect these driven issues by adding more and more controls to their systems, but the fact is one of the age old processes continues to operate within the same rules since the dawn of the SMT assembly world: The SMT screen printing. (...)This paper showcases a new stencil process that was discovered by reverting to the basics:understanding the reason for each stencil material process, focusing on detailed finishes and a disciplined aperture design process, maintaining original designs, and making the correctly designed apertures to control the paste deposition. The test results drove us to focus the efforts on the aperture walls In this paper we will demonstrate with lab tests SMT process results howthe improved paste release results in improved SMT print process performance and its positive impact on SPI yields and EOL performance.
Technical Library | 2023-05-22 16:42:56.0
Nano-coatings are applied to solder paste stencils with the intent of improving the solder paste printing process. Do they really make a noticeable improvement? The effect of Nano-coatings on solder paste print performance was investigated. Transfer efficiencies were studied across aperture sizes ranging from 0.30 to 0.80 area ratio. Also investigated were the effects of Nano-coatings on transfer efficiencies of tin-lead, lead-free, water soluble, no-clean, and type 3, 4, and 5 solder pastes. Solder paste print performance for each Nano-coating was summarized with respect to all of these variables.
Technical Library | 2022-12-05 16:28:06.0
The work evaluates the impact of latent heat (LH) absorbed or released by a solder alloy during melting or solidification, respectively, on changes of dimensions of materials surrounding of the solder alloy. Our sample comprises a small printed circuit board (PCB) with a blind via filled with lead-free alloy SAC305. Differential scanning calorimetry (DSC) was employed to obtain the amount of LH per mass and a thermomechanical analyzer was used to measure the thermally induced deformation. A plateau during melting and a peak during solidification were detected during the course of dimension change. The peak height reached 1.6 μm in the place of the heat source and 0.3 μm in the distance of 3 mm from the source. The data measured during solidification was compared to a numerical model based on the finite element method. An excellent quantitative agreement was observed which confirms that the transient expansion of PCB during cooling can be explained by the release of LH from the solder alloy during solidification. Our results have important implications for the design of PCB assemblies where the contribution of recalescence to thermal stress can lead to solder joint failure.
Technical Library | 2019-07-24 23:55:32.0
Voiding is a key concern for components with thermal planes because interruptions in Z-axis continuity of the solder joint will hinder thermal transfer. When assembling components with solder paste, there is a high propensity for voiding due to the confined nature of the solder paste deposits under the component. Once reflowed, many factors contribute to the amount of voiding in a solder joint such as the reflow profile, designs of the component, board and stencil, and material factors. This study will focus on the solder paste alloy and flux combination as well as profile and board surface finishes.
Technical Library | 2021-07-06 21:13:36.0
The surface finishes commonly used on printed circuit boards (PCBs) have an effect on solder paste performance in the surface mount process. Some surface finishes are non-planar like hot air solder level (HASL) which can lead to inconsistencies in solder paste printing. Other surface finishes are difficult to wet during reflow like organic solderability preservative (OSP). What is the overall effect of surface finish on solder paste performance? Which solder paste is best for each surface finish? It is the goal of this paper to answer these questions.
Technical Library | 2020-10-27 02:02:17.0
Solder powder size is a popular topic in the electronics industry due to the continuing trend of miniaturization of electronics. The question commonly asked is "when should we switch from Type 3 to a smaller solder powder?" Solder powder size is usually chosen based on the printing requirements for the solder paste. It is common practice to use IPC Type 4 or 5 solder powders for stencil designs that include area ratios below the recommended IPC limit of 0.66. The effects of solder powder size on printability of solder paste have been well documented. The size of the solder powder affects the performance of the solder paste in other ways. Shelf life, stencil life, reflow performance, voiding behavior, and reactivity / stability are all affected by solder powder size. Testing was conducted to measure each of these solder paste performance attributes for IPC Type 3, Type 4, Type 5 and Type 6 SAC305 solder powders in both water soluble and no clean solder pastes. The performance data for each size of solder powder in each solder paste flux was quantified and summarized. Guidance for choosing the optimal size of solder powder is given based on the results of this study.
Technical Library | 2016-11-30 21:30:50.0
Mid-chip solder balling is a defect typically associated with solder paste exhibiting poor hot slump and/or insufficient wetting during the reflow soldering process, resulting in paste flowing under the component or onto the solder resist. Once molten, this solder is compressed and forced to the side of the component, causing mid-chip solder balling.This paper documents the experimental work performed to further understand the impact on mid-chip solder balling from both the manufacturing process and the flux chemistry.
