Technical Library | 2018-11-06 12:42:25.0
Solder paste is a homogeneous, stable suspension of solder powder particles suspended in a flux binder, and is one of the most important process materials today in surface mount technology (SMT). By varying the solder particle size, distribution and shape, as well as the other constituent materials, the rheology and printing performance of solder pastes can be controlled. Paste flow behavior is very important in defining the printing performance of any paste.The purpose of this paper is to study the rheological behavior of SAC (Sn-Ag-Cu) solder paste used for surface mount applications in the electronic industry. The reason why the rheological tests are presented in this paper are two critical sub-processes: aperture filling and paste withdraw. In this paper, we report on the investigation of the rheological profiles, the serrated cone-to-plate system was found as effective in parameter minimizing the wall-slip effect
Technical Library | 2016-02-11 18:26:43.0
Although reflow ovens may not have been dramatically changed during the last decade the reflow process changes step by step. With the introduction of lead-free soldering not only operation temperatures increased, but also the chemistry of the solder paste was modified to meet the higher thermal requirements. Miniaturization is a second factor that impacts the reflow process. The density on the assembly is increasing where solder paste deposit volumes decreases due to smaller pad and component dimensions. Pick and place machines can handle more components and to meet this high through put some SMD lines are equipped with dual lane conveyors, doubling solder paste consumption. With the introduction of pin in paste to solder through hole components contamination of the oven increased due to dripping of the paste.
Technical Library | 2008-10-29 18:45:53.0
Growing demand for compact, multi-function electronics products has accelerated component miniaturization and high-density placement, creating new challenges for the electronics manufacturing industry. It is no longer adequate to simply place parts accurately per a pre-defined CAD assembly program because solder paste alignment errors are increasing for numerous reasons. The solution to this problem is a system in which the placement machine can automatically detect and compensate for misalignment of the solder paste to produce high-quality boards regardless of the process errors beforehand.
Technical Library | 2018-03-07 22:41:05.0
This study investigates the scooping effect during solder paste printing as a function of aperture width, aperture length and squeegee pressure. The percent of the theoretical volume deposited depends on the PWB topography. A typical bimodal percent volume distribution is attributed to poor release apertures and large apertures, where scooping takes place, yielding percent volumes 100%. This printing experiment is done with a concomitant validation of the printing process using standard 3D Solder Paste Inspection (SPI) equipment.
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.
Technical Library | 2014-10-02 20:10:07.0
Sn3.0Ag0.5Cu (SAC305) is the most popular near eutectic lead-free alloy used in the manufacturing processes. Over the last several years, the price of silver has dramatically increased driving a desire for lower silver alloy alternatives. As the results, there is a significant increase in the number of alternative low/no silver lead-free solder alloys available in the industry recently.In this paper, we'll present the performance and process capability of various low/no silver alloy solder pastes. Data from printability, wetting test, slump test, solder ball test, voiding, etc… will be discussed and compared with the control SAC305 solder paste. Benefits and concerns of using low/no silver alloy solder paste materials will also be addressed.
Technical Library | 2015-08-25 13:51:27.0
The stencil printing process is one of the most critical processes in the electronic production. Due to the requirement: "faster and smaller" it is necessary to place components with different paste volume close together without regard to solder paste printing. In our days it is no longer possible to control the solder paste volume only by adjustment of the aperture dimensions. The requirements of solder paste volumes for specific components are realized by different thicknesses of metal sheets in one stencil with so called step stencils. The step-down stencil is required when it is desirable to print fine-pitch devices using a thinner stencil foil, but print other devices using a thicker stencil foil. The paper presents the innovative technology of step-up and step-down stencils in a laser cutting and laser welding process. The step-up/step-down stencil is a special development for the adjustment of solder paste quantity, fulfilling the needs of placement and soldering. This includes the laser cutting and laser welding process as well as the resulting stencil characteristics and the potential of the printing process.
Technical Library | 2017-08-17 12:23:27.0
A novel epoxy flux EF-A was developed with good compatibility with no-clean solder pastes, and imparts high reliability for BGA assembly at a low cost. This compatibility with solder pastes is achieved by a well-engineered miscibility between epoxy and no-clean solder paste flux systems, and is further assured with the introduction of a venting channel. The compatibility enables a single bonding step for BGAs or CSPs, which exhibit high thermal warpage, to form a high-reliability assembly. Requirements in drop test, thermal cycling test (TCT), and SIR are all met by this epoxy flux, EF-A. The high viscosity stability at ambient temperature is another critical element in building a robust and userfriendly epoxy flux system. EF-A can be deposited with dipping, dispensing, and jetting. Its 75°C Tg facilitates good reworkability and minimizes the adverse impact of unfilled underfill material on TCT of BGA assemblies.
Technical Library | 2020-07-02 13:29:37.0
Industry standards such as J-STD-005 and JIS Z 3284-1994 call for the use of viscosity measurement(s) as a quality assurance test method for solder paste. Almost all solder paste produced and sold use a viscosity range at a single shear rate as part of the pass-fail criteria for shipment and customer acceptance respectively. As had been reported many times, an estimated 80% of the defects associated with the surface mount technology process involve defects created during the printing process. Viscosity at a single shear rate could predict a fatal flaw in the printability of a solder paste sample. However, false positive single shear rate viscosity readings are not unknown.
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