Whiskers growth on lead-free solder under dynamic stress

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F68407700%3A21230%2F15%3A00210907" target="_blank" >RIV/68407700:21230/15:00210907 - isvavai.cz</a>

Result on the web

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DOI - Digital Object Identifier

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Result language

angličtina

Original language name

Whiskers growth on lead-free solder under dynamic stress

Original language description

The global trend of reducing the use of elements and substances which have an adverse effect on the human body has left the response in the EU legislation. The European Parliament issued a directive in 2002 [1], which prohibit, or at least restricts, the usage of certain toxic substances and elements. One of these substances is lead. Lead in combination with tin forms eutectic alloy which is widely used for soldering electrical components on the printed circuit board (PCB) for its excellent mechanical and electrical properties and long term stability. Restrictions of the use of lead means a gradual transition to lead-free solder. Although their properties are inferior to leaded solders is practically the only alternative. With the new tin alloy without the presence of lead in time were a problem in terms of quality solder joints. For lead-free solders, however, a spontaneous growth of needle-shaped crystal structure which are called whiskers. It was shown that the presence of lead prevents their formation. They pose a risk in terms of reliability. These are outgrowths from the material surface with a diameter of 0,3-10 m reaching typically lenght around 500 m [2]. They can also have other shapes [3]. The growth of these conductive structure is undesirable for electrical circuits. Outgrows the whisker distance between two adjacent contacts can easily cause a short circuit and thus malfunction of PCB or adjacent connectors. The current in thin whiskers can reach values of the order of tens of mA [2]. Effective protection does not exist. Therefore, it is necessary to understand the causes of their origin. They haven’t been already fully understood. It is shown that for the growth of whiskers may increase tension (stress) within the solder alloy. This has several causes such as the presence of intermetallic alloy, the crystalline structure of the fault, a change of state, etc.

Czech name

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Czech description

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Type

O - Miscellaneous

CEP classification

JA - Electronics and optoelectronics

OECD FORD branch

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Project

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Continuities

S - Specificky vyzkum na vysokych skolach

Publication year

2015

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů