Researchers Submit Patent Application, "Method of Manufacturing Electronic Apparatus, Electronic Component-Mounting Board, and Method of Manufacturing the Same", for Approval
The patent's assignee is
News editors obtained the following quote from the background information supplied by the inventors: "In general, in the case where the processing speed and function of a large-scale integration (LSI) circuit are increased, the number of connection terminals of a semiconductor chip tends to correspondingly increase. A flip-chip mounting technique is employed as a connection technique, in which a solder bump formed on a semiconductor chip is utilized when the semiconductor chip faces downward. Examples of a material used to form the solder bump of a semiconductor chip include a tin (Sn)-silver (Ag) alloy, a tin-copper (Cu) alloy, and a tin-silver-copper alloy.
"In the flip-chip mounting technique, a solder bump is generally formed on an electrode of a semiconductor chip as described above, while a solder alloy is supplied also onto an electrode of a circuit board on which the semiconductor chip is to be mounted. In general, the solder alloy to be supplied onto the electrode of the circuit board has a primary component that is the same as that of the solder bump that is formed on the semiconductor chip. Such an approach is employed for the following reasons: solder wettability is improved at the time of forming a solder bump connection, solder is supplied at a finer pitch in a sufficient amount, and high connection reliability is maintained.
"In order to reduce production costs and provide a fine structure, a build-up substrate in which an organic material is used is employed as a circuit board. In the case where a semiconductor chip is bonded to a circuit board by using a material of the above solder bump, heat is applied at a high temperature higher than or equal to 250.degree. C., for example. By virtue of such application of heat, the solder bump of the semiconductor chip is melted as well as that of the circuit board, and then the melted solder bumps are fused together. Subsequently, the resultant product is cooled to complete the bonding process.
"In the cooling process, the state of a solder joint, which is formed as a result of fusing together the solder bumps, is changed from a liquid to a solid, and then the semiconductor chip is physically fixed to the circuit board. A circuit board that is produced by using an organic material exhibits a high thermal expansion coefficient that is in the range from 15 to 22 ppm/.degree.
"The usage of a low-melting-point solder has been suggested as an approach to overcome such a problem. Examples of the low-melting-point solder include Sn-58Bi solder having a melting point of 139.degree. C. and Sn-52In solder having a melting point of 115.degree. C. The usage of a low-melting-point solder serves as a technique for overcoming various problems due to the stress generated during the bonding process. However, usage of a low-melting-point solder in the semiconductor chips causes problems in that the solder is melted during a burn-in test of the semiconductor chip and in that the reliability with respect to electric properties may not be sufficiently evaluated.
"The followings are reference documents:
"[Document 1] Japanese Laid-open Patent Publication No. 10-41621
"[Document 2] International Publication Pamphlet No. WO 94/027777
"[Document 3] Japanese Laid-open Patent Publication No. 2007-208056"
As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "According to an aspect of the embodiment, a method of manufacturing an electronic apparatus including a first component and a second component, includes: forming a first solder bump on one of the first component and the second component; forming a second solder bump on the other one of the first component and the second component; bringing the first solder bump into contact with the second solder bump at a temperature higher than the liquidus temperature of any of the first and the second solder bumps such that the first and the second solder bumps are fused together to form a solder joint of an alloy having a lower liquidus temperature than any of the first and the second solder bumps; and solidifying the solder joint between the first and the second component.
"The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims.
"It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed.
BRIEF DESCRIPTION OF DRAWINGS
"FIGS. 1A to 1F are cross-sectional views each schematically illustrating a process of manufacturing a semiconductor device of an embodiment 1;
"FIG. 2 is a phase diagram illustrating the phase of Bi--Sn solder;
"FIGS. 3A to 3E are cross-sectional views each schematically illustrating a process of manufacturing a semiconductor device of an embodiment 2;
"FIG. 4 illustrates diameters of planarized surfaces and the variation range thereof, the planarized surfaces being formed as a result of planarizing the tops of solder bumps with a pressing machine;
"FIGS. 5A and 5B are photographs of the planarized top of the solder bumps;
"FIGS. 6A and 6B illustrate manufacturing conditions and manufacturing results in accordance with a method of manufacturing semiconductor devices of examples 1 to 31; and
"FIG. 7 illustrates manufacturing conditions and manufacturing results in accordance with a method of manufacturing semiconductor devices of examples 32 to 42."
For additional information on this patent application, see: Sakuyama, Seiki;
Keywords for this news article include: Electronics, Circuit Board, Semiconductor,
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