Technical Library | 2013-02-28 17:14:36.0
While it has long been known that the Cu6Sn5 intermetallic that plays a critical role in the reliability of solder joints made with tin-containing alloys on copper substrates exists in two different crystal forms over the temperature range to which electronics circuitry is exposed during assembly and service, it has only recently been recognized that the change from one form to the other has implications for solder joint reliability. (..) In this paper the authors report a study of the effect of cooling rates on Cu6Sn5 crystals. Cooling rates from 200°C ranged from 10°C/minute to 100°C/minute and the effect of isothermal ageing at intermediate temperatures was also studied. The extent of the phase transformation after each regime was determined using synchrotron X-ray diffraction. The findings have important implications for the manufacture of solder joints and their in-service performance... First published in the 2012 IPC APEX EXPO technical conference proceedings....
Technical Library | 2014-08-19 15:39:13.0
Understanding warpage of package attach locations on PCBs under reflow temperature conditions is critical in surface mount technology. A new industry standard, IPC 9641, addresses this topic directly for the first time as an international standard.This paper begins by summarizing the sections of the IPC 9641 standard, including, measurement equipment selection, test setup and methodology, and accuracy verification. The paper goes further to discuss practical implementation of the IPC 9641 standards. Key advantages and disadvantages between available warpage measurement methods are highlighted. Choosing the correct measurement technique depends on requirements for warpage resolution, data density, measurement volume, and data correlation. From industry experience, best practice recommendations are made on warpage management of PCB land areas, covering how to setup, run, analyze, and report on local area PCB warpage.The release of IPC 9641 shows that flatness over temperature of the package land area on the PCB is critical to the SMT industry. Furthermore, compatibility of shapes between attaching surfaces in SMT, like a package and PCB, will be critical to product yield and quality in years to come.
Technical Library | 2019-05-01 23:18:27.0
Moisture can accelerate various failure mechanisms in printed circuit board assemblies. Moisture can be initially present in the epoxy glass prepreg, absorbed during the wet processes in printed circuit board manufacturing, or diffuse into the printed circuit board during storage. Moisture can reside in the resin, resin/glass interfaces, and micro-cracks or voids due to defects. Higher reflow temperatures associated with lead-free processing increase the vapor pressure, which can lead to higher amounts of moisture uptake compared to eutectic tin-lead reflow processes. In addition to cohesive or adhesive failures within the printed circuit board that lead to cracking and delamination, moisture can also lead to the creation of low impedance paths due to metal migration, interfacial degradation resulting in conductive filament formation, and changes in dimensional stability. Studies have shown that moisture can also reduce the glass-transition temperature and increase the dielectric constant, leading to a reduction in circuit switching speeds and an increase in propagation delay times. This paper provides an overview of printed circuit board fabrication, followed by a brief discussion of moisture diffusion processes, governing models, and dependent variables. We then present guidelines for printed circuit board handling and storage during various stages of production and fabrication so as to mitigate moisture-induced failures.
Technical Library | 2019-05-08 01:46:32.0
IPX9K Rain Spray Test Chamber(high Pressure high temperature water jet) simulates the use of pressure washer steam cleaning onto the enclosure, It is recognised as the harshest of all ingress protection tests. However the requirement is becoming more prevalent across many industries. Test method for IPX9K : Make sure the water temperature inside the water tank +80°C, water flow rate with 14L-16L per min, water pressure: 8000 Kpa -10000 Kpa (80–100 bar) at distance of 100mm~ 150mm, The test duration is 30 seconds in each of 4 angles, total spray testing time is 2 minutes. IPX9K rain test chamber applicable standards: IEC 60529 – Degrees of protection provided by enclosures (IP Code).Here is working principle in picture. Application: It is mainly suitable for testing the performance of shell and seal of electrical and electronic parts, automobile parts and seals under the condition of dripping rain to prevent Rain Water from permeating or working after drizzling.
Technical Library | 2020-12-16 18:38:49.0
Fabrication of large structures using out-of-autoclave prepreg materials will lead to a great amount of savings in manufacturing costs. In the out-of-autoclave processing method, the presence of voids inside the laminate has been an issue due to the lack of high pressure during manufacturing. This study aims primarily to observe the moisture absorption response of composite samples containing different levels of void. By changing the vacuum level inside the bag during the manufacturing process, three different unidirectional laminates at three levels of void have been manufactured. After immersing the samples in warm water at 60°C for about one year, the moisture absorption level was monitored and then diffusion coefficients were calculated using Fick's law. Results show that the moisture absorption coefficient changes by %8 within the experimental range of void contents. The mechanical behaviour of these laminates has been studied at four different moisture levels by performing dynamic mechanical analysis (DMA) and short beam shear tests. Empirical results indicate that, in general, interlaminar shear strength and glass transition temperature decrease by moisture build-up inside the samples. DiBenedetto equation is proposed to make a correlation between the moisture content and glass transition temperature.
Technical Library | 2022-10-31 17:25:37.0
Mixed formulation solder alloys refer to specific combinations of Sn-37Pb and SAC305 (96.5Sn–3.0Ag–0.5Cu). They present a solution for the interim period before Pb-free electronic assemblies are universally accepted. In this work, the surfaces of mixed formulation solder alloys have been studied by in situ and real-time Auger electron spectroscopy as a function of temperature as the alloys are raised above the melting point. With increasing temperature, there is a growing fraction of low-level, bulk contaminants that segregate to the alloy surfaces. In particular, the amount of surface C is nearly _50–60 at. % C at the melting point. The segregating impurities inhibit solderability by providing a blocking layer to reaction between the alloy and substrate. A similar phenomenon has been observed over a wide range of (SAC and non-SAC) alloys synthesized by a variety of techniques. That solder alloy surfaces at melting have a radically different composition from the bulk uncovers a key variable that helps to explain the wide variability in contact angles reported in previous studies of wetting and adhesion. VC 2011 American Vacuum Society. [DOI: 10.1116/1.3584821]
Technical Library | 2023-08-04 15:27:30.0
A designed experiment evaluated the influence of several variables on appearance and strength of Pb-free solder joints. Components, with leads finished with nickel-palladium-gold (NiPdAu), were used from Texas Instruments (TI) and two other integrated circuit suppliers. Pb-free solder paste used was tin-silver-copper (SnAgCu) alloy. Variables were printed wiring board (PWB) pad size/stencil aperture (the pad finish was consistent; electrolysis Ni/immersion Au), reflow atmosphere, reflow temperature, Pd thickness in the NiPdAu finish, and thermal aging. Height of solder wetting to component lead sides was measured for both ceramic plate and PWB soldering. A third response was solder joint strength; a "lead pull" test determined the maximum force needed to pull the component lead from the PWB. This paper presents a statistical analysis of the designed experiment. Reflow atmosphere and pad size/stencil aperture have the greatest contribution to the height of lead side wetting. Reflow temperature, palladium thickness, and preconditioning had very little impact on side-wetting height. For lead pull, variance in the data was relatively small and the factors tested had little impact.
Technical Library | 2024-04-08 15:46:36.0
A designed experiment evaluated the influence of several variables on appearance and strength of Pb-free solder joints. Components, with leads finished with nickel-palladium-gold (NiPdAu), were used from Texas Instruments (TI) and two other integrated circuit suppliers. Pb-free solder paste used was tin-silver-copper (SnAgCu) alloy. Variables were printed wiring board (PWB) pad size/stencil aperture (the pad finish was consistent; electrolysis Ni/immersion Au), reflow atmosphere, reflow temperature, Pd thickness in the NiPdAu finish, and thermal aging. Height of solder wetting to component lead sides was measured for both ceramic plate and PWB soldering. A third response was solder joint strength; a "lead pull" test determined the maximum force needed to pull the component lead from the PWB. This paper presents a statistical analysis of the designed experiment. Reflow atmosphere and pad size/stencil aperture have the greatest contribution to the height of lead side wetting. Reflow temperature, palladium thickness, and preconditioning had very little impact on side-wetting height. For lead pull, variance in the data was relatively small and the factors tested had little impact.
Technical Library | 2007-12-20 16:28:08.0
Despite much research and discussion on the subject of reflow profiling, many questions and a good deal of confusion still exist. What is clear is that the pains often associated with profiling can be reduced if there is a strong understanding of the variables that can be encountered during the reflow process, as well as the metallurgical dynamics of the soldering process. This paper shall provide a brief outline of the reflow profile in general, with specific emphasis placed upon the suggested time spent above the melting temperature of the solder. The guidelines for soldering to various surfaces and with alternative solder alloys also are discussed.
Technical Library | 2012-11-27 14:06:48.0
Quality managers and line supervisors are routinely tasked with the responsibility of ensuring that the hand soldering process is under control. The method most commonly used is to measure the idle tip temperature of the soldering station and to use this reading as a benchmark of system compliance. This method, although popular is now being seriously questioned by many industry professionals as being irrelevant in qualifying true system process control. This document aims to present a practical view of what factors are important for successful hand soldering and to suggest an alternative procedure for qualification that is simple, repeatable and directly related to the effectiveness of the soldering station.
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