Quantitative Solderability Measurement of Electronic ComponentsLea, C.
1991 Soldering & Surface Mount Technology
doi: 10.1108/eb037749
The three European Community manufacturers of commercially available wetting balances for measuring the solderability of electronic components have participated in an intercomparison assessment of surfaces of standard solderability that have the potential for calibrating the balance instruments. The development of the standard surfaces, as well as the small adjustments needed to improve the uniformity of design of the different instruments, and the standardisation of the procedures for their use, have been described in the preceding papers in this series. This paper gives details of the experimental procedures used for the intercomparison and the significance of the comparative data from each balance type.
Water Soluble Fluxes, their Reliability and their Usefulness as a Means of Eliminating CFC113 UsageEllis, B.N.
1991 Soldering & Surface Mount Technology
doi: 10.1108/eb037751
This paper outlines the composition of water soluble fluxes for the electronics industry and their methods of use when wave soldering and reflowing tinned coatings and solder pastes. Process optimisation is facilitated by the Taguchi method. Three types of cleaning machinery are evoked, with varying results. It is shown that the energytime relationship is important to ensure adequate cleaning quality. A number of fallacious arguments are debunked. Methods of water purification and the problems of effluent treatment for all sizes of installation are addressed. Doubt is expressed as to the viability of closedcircuit water recycling except for the largest installations or where exceptional conditions prevail. It is shown that water soluble fluxes and their subsequent aqueous removal are unlikely to make any significant contribution to the Greenhouse Effect. The overall cost of their use is substantially similar to that of rosin fluxes with CFC113 azeotropes at 1986 prices. Cleanliness control under production and laboratory conditions is discussed with reference to both ionic contamination testing, including its use for SMDs, and SIR analysis, especially at low voltages, including nondestructive production SIR testing. Reliability of the assembled circuits is shown to be at least as good as that with more traditional soldering and cleaning methods, frequently better, and this is the case even for military and aerospace applications. The paper concludes that, now that quality water soluble solder pastes are available, this method is most likely to become the workhorse for the majority of electronics applications.
Experimental Investigation and Numerical Simulation of the SMT Laser Microsoldering Thermal ProcessWang, C.Q.; Qian, Y.Y.; Jiang, Y.H.
1991 Soldering & Surface Mount Technology
doi: 10.1108/eb037753
In this paper, a numerical simulation of the thermal process in SMT laser microsofdered joints has been developed, in which the influences on the thermal process of factors such as the thermal conductivity variation of solder with temperature, light reflection coefficient of the lead wire surface, and heat transfer on the surface of SMT materials have all been considered. In order to put this numerical calculation into practice and prove its results, the reflective characteristic of light waves in relation to SMT materials has been determined, and the dynamic temperature process of laser soldered microjoints has been measured by a new experimental method invented by the authors. The numerical simulation results have been borne out by the tests, and the influence of heating parameters on the thermal process has been analysed in this paper. The conclusions will benefit the further study of microjoint quality control in SMT laser microsoldering.
The Impact of Crevices beneath Surface Mounted Devices on the Cleaning EfficiencyTegehall, P.E.
1991 Soldering & Surface Mount Technology
doi: 10.1108/eb037754
The transition to surface mounted device SMD technology in electronics manufacturing has placed new demands on the postsolder cleaning process. For spacecraft electronic systems it is of the utmost importance that all flux residues be removed. This paper reports the results of an investigation of the impact of component standoff heights and the distance between solder joints on the cleaning process efficiency. The capability to clean beneath large chip carriers was evaluated for four different cleaning methods using isopropanol or CFC113 Freon TMS as cleaning liquid. The results show that the cleaning efficiency decreases considerably if the standoff height is less than 240 m for 100 mil pitch chip carriers. For 50 mil pitch chip carriers the standoff height needs to be greater than 240 m to achieve high cleaning efficiency. The cleaning efficiency beneath chip carriers with small standoff heights can be increased by using ultrasonic cleaning. However, a very thin layer of white residues is left where the flux has been removed if isopropanol is used as the cleaning liquid.
SMART group newsWood, Tony
1991 Soldering & Surface Mount Technology
doi: 10.1108/eb037756
This designbased seminar was aimed at broadening the horizons of designers and engineers. The greatest area of cost reduction in any electronics project is in making the right choices at the conception and design phases. This seminar was one step in this direction a piece of 16 mm FR4 is not always the best substrate to use.
Industry news1991 Soldering & Surface Mount Technology
doi: 10.1108/eb037758
Due to recent expansion A.R.T., specialising in rework technology, has appointed Graham Devenish as Technical Director. Mr Devenish has been involved with the company for many years as a partner and feels that the time is now right for him to become more actively involved. He has gained a wealth of technical experience in the field of electronics, working for companies such as Marconi and Cable & Wireless. His experience in the Marconi Field Services Division has provided him with invaluable knowledge for identifying and solving technical problems. Mr Devenish will provide backup for existing courses and will also initiate future training programmes.
New Products1991 Soldering & Surface Mount Technology
doi: 10.1108/eb037759
Stork Graphics has recently introduced the HiMesh Mask specially suited to surface mount technology applications. This screen printing mask, made of 100 nickel, differs from metal masks and traditional stainless steel or polyester mesh in that it encompasses many of the advantages of both. It has the flexibility of a steel or polyester screen combined with the typical stencil qualities of zero deformation and dimensional stability. The hexagonal structure, and therefore the wall and hole shape, means that both on and off contact printing are possible. Additionally, this material provides a very uniform and flat deposit, an essential criterion in the application of solder paste.