Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
1995-09-12
2001-02-06
Gaffin, Jeffrey (Department: 2841)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S257000, C228S248100, C228S224000, C420S557000, C420S562000
Reexamination Certificate
active
06184475
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to manufacturing of electric and electronic apparatuses and more particularly to a solder alloy of various forms used for soldering electric and electronic components, as well as to a soldering process and further to a rig used for such a soldering process. In particular, the present invention relates to a lead-free solder alloy that contains no substantial amount of lead (Pb).
Solder alloys are characterized by low melting temperatures and provide excellent electric as well as mechanical properties. Thus, solder alloys of various forms, including solder powders and solder pastes, are used for mounting electronic components on a printed circuit board.
Meanwhile, conventional solder alloys contain Pb. As Pb is toxic against biological bodies, it has been necessary to take precautionary measure when conducting such a soldering process, while such a precautionary measure increases the cost of the products produced as a result of the soldering. Thus, there is a demand for a lead-free solder alloy that is suitable for use in various soldering processes including automated soldering process.
In the automated soldering process of electronic components, several types of solder alloys are used conventionally. A representative example is a solder alloy known as Sn63-Pb37, wherein the solder alloy contains 63 wt % of Sn and 37 wt % of Pb. This material causes an eutectic melting at a melting temperature of 183° C. Another typical example is a solder alloy known as Sn62-Pb36-Ag2, wherein the solder alloy contains 62 wt % of Sn, 36 wt % of Pb and 2 wt % of Ag. The solder alloy forms an eutectic system characterized by a melting temperature of 179° C. As these solder alloys have low melting temperatures and provide excellent mechanical properties in terms of tensile strength and elongation as well as excellent electrical properties such as low resistance, they are used extensively for various automated soldering processes.
Meanwhile, there is a tendency of increasing public regulations against the use of Pb in view of human health and in view of environmental protection. Under such circumstances, various efforts have been made for developing a substitute solder alloy that is free from Pb.
As the material for use in assembling electric and electronic apparatuses, such a substitute solder alloy is required to have a low melting temperature such that the soldered electric or electronic component experiences little degradation of performance caused by the heat at the time of soldering. Further, such a substitute solder alloy should have an excellent mechanical strength comparable to that of a conventional solder alloy that contains Pb.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of the present invention to provide a novel and useful solder alloy of various forms as well as a soldering process wherein the foregoing problems are eliminated.
Another and more specific object of the present invention is to provide a solder alloy free from Pb and still having a sufficiently low melting temperature, high conductivity and high mechanical strength.
Another object of the present invention is to provide a lead-free solder alloy composition comprising Sn, Bi and In, said solder alloy containing Sn, Bi and In with respective concentrations set such that said lead-free solder alloy composition has a melting temperature lower than a predetermined heat-resistant temperature of a work to be soldered.
Another object of the present invention is to provide a method for soldering a work, comprising the steps of:
reflowing a lead-free solder alloy containing therein Sn, Bi and In with respective contents set such that said solder alloy has a melting temperature lower than a predetermined heat-resistant temperature of said work, said step of reflowing including a step of heating said solder alloy to a temperature higher than said melting temperature; and
cooling said work at a part where a soldering has been made to solidify said lead-free solder alloy.
Another object of the present invention is to provide a lead-free solder alloy composition containing: Bi with a concentration not exceeding 60.0 wt %; In with a concentration not exceeding 50.0 wt %; one or more elements selected from a group consisting of Ag, Zn, Ge, Ga, Sb and P, with a concentration equal to or larger than 1.0 wt % but lower than 5.0 wt %; and Sn as a balancing component of said lead-free solder alloy.
Another object of the present invention is to provide a soldering process of a work, comprising the steps of:
reflowing a lead-free solder alloy containing therein: Bi with a concentration not exceeding 60.0 wt %; In with a concentration not exceeding 50.0 wt %; one or more elements selected from a group consisting of Ag, Zn, Ge, Ga, Sb and P, with a concentration equal to or larger than 1.0 wt % but lower than 5.0 wt %; and Sn as a remaining component of said solder alloy; and
cooling said work at a part where a soldering is made to solidify said lead-free solder alloy.
Another object of the present invention is to provide a lead-free solder alloy composition containing Sn, Ag and Bi, with respective concentrations set such that said lead-free solder alloy has a melting temperature lower than a predetermined heat-resistant temperature of a work to be soldered.
Another object of the present invention is to provide a method of soldering a work, comprising the step of:
reflowing a lead-free solder alloy containing therein Sn, Ag and Bi with respective contents set such that said lead-free solder alloy has a melting temperature lower than a predetermined heats-resistant temperature of said work, said step of reflowing including a step of heating said lead-free solder alloy to a temperature higher than said melting temperature; and
cooling said work at a part where a soldering is made to solidify said lead-free solder alloy.
Another object of the present invention is to provide a lead-free solder powder comprising:
a plurality of lead-free solder particles each having a generally spherical shape with a diameter of 20-60 &mgr;m;
each of said lead-free solder particles containing Sn, Bi and In, with respective concentrations set such that said lead-free solder particle has a melting temperature lower than a predetermined heat-resistant temperature of a work to be soldered.
Another object of the present invention is to provide a lead-free solder powder comprising:
a plurality of lead-free solder particles each having a generally spherical shape with a diameter of 20-60 &mgr;m;
each of said lead-free solder particles containing Bi with a concentration not exceeding 60.0 wt %; In with a concentration not exceeding 50.0 wt %; one or more elements selected from a group consisting of Ag, Zn, Ge, Ga, Sb and P, with a concentration equal to or larger than 1.0 wt % but lower than 5.0 wt %; and Sn as a remaining component of said lead-free solder particle.
Another object of the present invention is to provide a lead-free solder powder comprising:
a plurality of lead-free solder particles each having a generally spherical shape with a diameter of 20-60 &mgr;m;
each of said lead-free solder particles containing Sn, Ag and Bi, with respective concentrations set such that said lead-free solder alloy has a melting temperature lower than a predetermined heat-resistant temperature of a work to be soldered.
Another object of the present invention is to provide lead-free solder paste, comprising:
a lead-free solder powder comprising a plurality of lead-free solder particles each having a generally spherical shape with a diameter of 20-60 &mgr;m; each of said lead-free solder particles containing Sn, Bi and In, with respective concentrations set such that said lead-free solder particle has a melting temperature lower than a predetermined heat-resistant temperature of a work to be soldered, said solder powder being contained with a proportion of 80.0-95.0 wt %; and
a mixture of an amine halide, a polyhydric alcohol and a polymer, with a proportion of 20.0-5.0 wt %.
Another object of the pres
Fukushima Yumiko
Kitajima Masayuki
Moriya Yasuo
Nemoto Yoshinori
Takesue Masakazu
Arent Fox Kintner & Plotkin & Kahn, PLLC
Cuneo Kamand
Fujitsu Limited
Gaffin Jeffrey
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