Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1999-01-21
2001-04-03
Young, Lee (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S832000, C029S840000, C029S846000, C029S877000, C029S878000
Reexamination Certificate
active
06209196
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for mounting bumped electronic components to a board or substrate.
As a means for mounting electronic parts onto electrodes of a circuit pattern on a board, there has been known a method which forms solder portions, such as solder bumps and solder precoats, on electronic components to be mounted or on electrodes of the board beforehand and joins the electronic components to the electrodes of the board by means of the solder portions. The soldering process involves applying a flux to the solder portions or the electrodes of the board, mounting the electronic components onto the electrodes, and heating and melting the solder to join the solder portions and the electrodes together. After the solder joints have been formed, the assembly is subjected to cleaning to remove flux residues to enhance the reliability after the mounting, followed by filling an underfill resin into gaps between the bumped electronic parts and the board to reinforce the joints. The underfill resin is then hardened by heat treatment, thus completing the mounting process.
The bumped electronic parts mounting process described above, however, poses the following problems as the electronic parts are miniaturized. First, because the use of such solvents as fluorocarbon, which have been in wide use, for cleaning is restricted by law, the cleaning process after soldering has become complicated and risen in cost, which, combined with on-going reductions in the size of electronic components, has contributed to making the cleaning process technically difficult. As to the underfill resin, miniaturization of electronic components reduces the gaps between the electronic components and the board and therefore makes the filling of resin after the mounting of electronic components difficult, resulting in unstable quality of the assembly. In addition to this quality problem, the above conventional mounting method has another problem that it requires two heating processes for the mounting of each component, one for soldering and one for hardening the resin, thus complicating the process.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a bumped electronic component mounting method which does not use fluxes in the soldering of the mounting process and has low cost and high reliability after mounting.
According to the feature of the present invention, there is provided a method of mounting bumped electronic components, comprises the steps of: applying a resin adhesive containing a filler to a board formed with electrodes; mounting a bumped electronic component formed with solder bumps onto the board; pressing the solder bumps of the bumped electronic component against the electrodes of the board to break oxide films formed over the surfaces of the solder bumps with the filler; and heating the solder bumps to join the bumped electronic component to the electrodes.
According to another feature of the present invention, there is provided a method of mounting bumped electronic components, comprises the steps of: applying a resin adhesive containing a filler to a board formed with electrodes and with solder precoats over the electrodes; mounting a bumped electronic component formed with solder bumps onto the board; pressing the solder bumps against the solder precoats formed over the electrodes of the board to break oxide films formed over the surfaces of the solder bumps and the solder precoats with the filler; and heating the solder bumps and the solder precoats to join the bumped electronic component to the electrodes.
According to still another feature of the present invention, there is provided a method of mounting bumped electronic components as mentioned above, in which a high melting point solder is used as a solder material for either the solder bumps of the electronic component or the solder precoats over the electrodes of the board and a low melting point solder is used as a solder material for the other.
According to further feature of the present invention, there is provided a method of mounting bumped electronic components, comprises the steps of: applying a resin adhesive containing a filler to a board formed with electrodes and with solder precoats over the electrodes; mounting a bumped electronic component formed with metal bumps onto the board; pressing the metal bumps against the solder precoats formed over the electrodes of the board to break oxide films formed over the surfaces of the solder precoats with the filler; and heating the solder precoats to join the bumped electronic component to the electrodes.
According to still further feature of the present invention, there is provided a method of mounting bumped electronic components, comprises the steps of: applying a resin adhesive containing a filler to a board formed with electrodes and with metal bumps over the electrodes; mounting a bumped electronic component formed with solder bumps onto the board; pressing the solder bumps against the metal bumps formed over the electrodes of the board to break oxide films formed over the surfaces of the solder bumps with the filler; and heating the solder bumps to join the bumped electronic component to the metal bumps of the electrodes.
According to the present invention as set forth in the appended claims, the resin adhesive containing a filler is applied to the board prior to the mounting of the bumped electronic component, and the solder portions are pressed against the electrodes or against the solder portions or metal bumps formed over the electrodes with the filler interposed therebetween to break the oxide films on the surfaces of the solder portions, thereby making it possible to solder the electronic component to the electrodes of the board without using a flux. As mentioned above, while the oxide films on the surfaces of the solder portions are broken by the deformation of the solder itself under pressure in the mounting process, according to the present invention as set forth in the appended claims, the oxide films are more effectively broken by the resin adhesive containing a filler, so that the reliability of the mounting is effectively enhanced.
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Eifuku Hideki
Ozono Mitsuru
Sakai Tadahiko
Kim Paul D.
Matsushita Electric - Industrial Co., Ltd.
Stevens Davis Miller & Mosher LLP
Young Lee
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