March 2026 Continued from previous page
of only a month of room temperature storage between soldering and testing. Metal lurgical science already had an explanation for that behaviour and also the strengthening effect of the Ag3Sn. When closely spaced, particles act as barriers to the movement of the disloca- tions, the defect in the crystal lattice of metals that makes it possible for them to deform in response to relatively low stress. However, small particles with a large surface area to volume ratio are thermodynamically unstable with atoms migrating to the larger particles in the process known as Ostwald ripening. The strengthening effect of the particle
is explained by the Orowan mechanism that defines the relationship between the strengthening effect and the size and spacing of the particles. The strengthening effect is at its maximum when the particles are small and closely spaced. When, as a result of Ostwald ripening, the particle size and the space be- tween particles increase their ef- fectiveness in blocking disloca- tion movement fades.
Silver-Free Solders Available Even at the time that the EU
Directive came into force, the Nihon Superior silver-free RoHS- compliant alloy SN100C was be- ing widely used in wave soldering and evidence of the reliability of the electronics assemblies manu- factured with that alloy was accu- mulating. Assemblies manufac- tured at that time went on to de- liver long service lives confirming that in actual application they could at least match the reliabili- ty of the silver-containing alterna- tives. The excellent performance in wave soldering and later in se- lective soldering justified the slightly higher solder tempera- ture required to achieve optimum hole fill and fillet formation.
A More Stable Strengthener A question that has to be
asked about the first round of lead-free solder alloy develop- ment is why the strengthening mechanism that delivered the re- liability that is so highly regard- ed in tin-lead solder was ignored. That mechanism is solid-solution strengthening, in which the dis- location movement in the tin ma- trix of the solder joint is re- strained by atoms of another ele- ment that distort the crystal lat- tice through which the disloca- tions have to move. In tin-lead solders both the
lead phase and the tin phase ben- efit by solid solution strengthen- ing: tin dissolved in the lead and lead dissolved in the tin. Options for RoHS-compliant elements that have solid state solubility in tin are limited but non-toxic bismuth stood out as a promising option. In recognizing the potential
of bismuth as an additive to his SN100C alloy, Nihon Superior’s Tetsuro Nishimura understood the need to set the level of the ad- dition to less than the solid solu-
www.us-tech.com The Move to Silver-Free Solder is Well Underway...
bility limit in tin at service temperatures. The precipitation of bismuth from super- saturated tin during the cool part of a thermal
cycle, and its redissolution at the temperature increases introduces an instability into the mi- crostructure that can compromise reliability. Because of the solid solutions’ strengthening by bismuth, SN100CV, can at least match the reliability of tin-silver-copper solders. As a bonus, because the bismuth addition lowers the melting temperature range, SN100CV paste can be reflowed with the same profile used to reflow tin-silver-copper solder paste. Contact: Nihon Superior USA, LLC,
Tetsuro Nishimura, president, Nihon Superior.
1395 Hawk Island Drive, Osage Beach, MO 65065 % 573-280-2357 E-mail:
s.memita@
nihonsuperior.co.jp Web:
www.nihonsuperior.com r
See at APEX Expo, Booth 1129
Blazing Speed. Unmatched Precision. SQ5000™
Pro Multi-Function 3D AOI, SPI & CMM
Page 47
ADVANCED High Speed
MRS Sensors Resolution and High
AOI
SPI
CMM
For Superior Inspection and Metrology Performance. – Metrology-grade accuracy with multi-award-winning Multi-Reflection Suppression® (MRS®) technology that mitigates reflection based distortions from shiny surfaces.
– High-Resolution and high-speed sensor options. – Faster and smarter with AI-Enabled AutoProgram™
, AutoTeach™ , AutoDefine™ streamline processes – All part of the Nordson Intelligence Ecosystem. – Multi-functionality for AOI, SPI and capturing coordinate measurements (CMM) in-line, in seconds with NordsonCMM. Nordson Sight Soſtware – Fast, Intuitive and Scalable SPC Solution Save Time. Save Expense. Improve Yields.
nordson.com/testinspect | +1 760.918.8471 Copyright © Nordson Corporation. All rights reserved.
and AutoTune™ to minimize operation and
See at APEX Expo, Booth 1831
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100
