Technical Library | 2021-02-20 00:55:47.0
Customers must be able to rely on accurate humidity indication as an assurance of SMD quality and fitness for processing and use. Without it, they might accept SMDs from suppliers that have already been irreparably damaged by moisture during storage or transit. Or, they might approve for processing SMDs that have been improperly or insufficiently heat-dried. Beyond the processing questions, there are financial questions: Where did the dry pack problems originate and who--supplier, customer, shipper--is financially responsible for the damaged SMDs? In response, Clariant, the originator of the color change humidity indicator card, and a member of the JEDEC's Subcommittee 14.1, "Reliability and Test Methods for Packaged Devices," created a new "non-reversible" halogen and cobalt dichloride free humidity indicator card. This HIC combines two reversible indicators (5% and 10%) with a new non-reversible (60% RH) indicator spot. (Figure 1) The 5% and 10% reversible spots work the way similar indicators do: they change color from blue (dry), to lavender, to pink (wet) to indicate humidity exposure at the indicated levels. If humidity levels drop, they will gradually revert back to blue.
Technical Library | 2008-11-20 00:46:10.0
The Sn/Ag/Cu family of alloys is the leading candidate for a lead-free alternative. The first part of this study was to determine if there is any significant difference between Sn/Ag/Cu alloys when used in automatic soldering equipment in terms of copper build-up in the system. The study compared two Sn/Ag/Cu alloys to determine if at processing temperatures one alloy would absorb less copper than the other alloy.
Technical Library | 2019-06-20 00:09:49.0
It is well known that during service the layer of Cu6Sn5 intermetallic at the interface between the solder and a Cu substrate grows but the usual concern has been that if this layer gets too thick it will be the brittleness of this intermetallic that will compromise the reliability of the joint, particularly in impact loading. There is another level of concern when the Cu-rich Cu3Sn phase starts to develop at the Cu6Sn5/Cu interface and an imbalance in the diffusion of atomic species, Sn and Cu, across that interface results in the formation at the Cu3Sn/Cu interface of Kirkendall voids, which can also compromise reliability in impact loading. However, when, as is the case in some microelectronics, the copper substrate is thin in relation to the volume of solder in the joint an overriding concern is that all of the Cu will be consumed by reaction with Sn to form these intermetallics.This paper reports an investigation into the kinetics of the growth of the interfacial intermetallic, and the consequent reduction in the thickness of the Cu substrate in solder joints made with three alloys, Sn-3.0Ag-0.5Cu, Sn-0.7Cu-0.05Ni and Sn-1.5Bi-0.7Cu-0.05Ni.
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