A method of forming a solder film on a metallic surface such as a pad of a metallic circuit of a printed circuit board and a lead frame of electronic parts, which is capable of forming a precise and fine pattern and which comprises selectively imparting tackiness to only a predetermined part of the metallic surface by means of a tacky layer-forming solution, adhering a powdered solder to the resulting tacky part, and then melting the solder by heating to thereby form a solder film.
This is a divisional of application Ser. No. 08/332,488, now U.S. Pat. No. 5,556,023, filed Oct. 31, 1994, which is a file wrapper continuation-in-part of prior application Ser. No. 08/144,322 filed Nov. 1, 1993 (abandoned).
Priority Data
Oct 30, 1992 [JP] 4-315738 Jan 11, 1993 [JP] 5-19366
The present invention provides a soldering method and a soldered joint securing a strength of joint equivalent to soldering using a conventional Pb--Sn solder alloy without having a detrimental effect on the environment and without causing a rise in cost. A soldering method comprising a step of covering Cu electrodes of electronic equipment by a rust-proofing coating consisting of an organic compound including N and a step of forming soldered joints on the covered Cu electrodes, by using a solder material consisting of at least 2.0 wt % and less than 3 wt % of Ag, 0.5 to 0.8 wt % of Cu, and a balance of Sn and unavoidable impurities. The solder material used in the present invention further contains not more than 3 wt % in total of at least one element selected from the group consisting of Sb, In, Au, Zn, Bi, and Al.
A circuit board mounted with a semiconductor device is fabricated by forming on a silicon substrate at least one first metal layer, overlaying a second metal layer to completely cover the first metal layer, covering the whole surface of the second metal layer with an insulating material, etching the insulating material to open a window at a prescribed region of the surface of the second metal layer, selectively imparting adhesiveness to the portion at the window, adhering solder powder to the adhesive portion, melting the solder powder by heating to form a solder bump, selectively imparting adhesiveness to at least one electrode portion of a wiring board, adhering solder powder to the adhesive portion, melting the adhered solder powder by heating to form a solder bump on the electrode portion, and contacting and fusing the solder bump of the silicon substrate and the solder bump of the wiring board so as to form and maintain a prescribed gap between the silicon substrate and the wiring board.
In accordance with the present invention, a method of treating the surface of an organic substrate, particularly a circuitized surface of an organic substrate, which method reduces the spread of adhesive resin that is subsequently deposited on the surface, is provided. This method comprises the steps of applying a treatment solution comprising a fatty acid compound, an alkalizing agent, and a solvent comprising water and from about 5% to about 90% by volume of an organic solvent selected from the group consisting of an alcohol, a glycol ether, and combinations thereof to the surface; and then removing substantially all of the solvent from the solution to provide a thin film on the surface of said substrate. The film comprises the fatty acids that were present in the treatment solution. In a preferred embodiment the treatment solution further comprises a chelating agent. The present invention also relates to a treatment solution for reducing adhesive resin bleed on the surface of a circuitized organic substrate. The present invention also relates to a circuitized organic substrate that is resistant to resin bleed. Such substrate has a film comprising a fatty acid compound disposed on the circuitized surface thereto.
A circuit board mounted with a semiconductor device is fabricated by forming on a silicon substrate at least one first metal layer, overlaying a second metal layer to completely cover the first metal layer, covering the whole surface of the second metal layer with an insulating material, etching the insulating material to open a window at a prescribed region of the surface of the second metal layer, selectively imparting adhesiveness to the portion at the window, adhering solder powder to the adhesive portion, melting the solder powder by heating to form a solder bump, selectively imparting adhesiveness to at least one electrode portion of a wiring board, adhering solder powder to the adhesive portion, melting the adhered solder powder by heating to form a solder bump on the electrode portion, and contacting and fusing the solder bump of the silicon substrate and the solder bump of the wiring board so as to form and maintain a prescribed gap between the silicon substrate and the wiring board.
In accordance with the present invention, a method of treating the surface of an organic substrate, particularly a circuitized surface of an organic substrate, which method reduces the spread of adhesive resin that is subsequently deposited on the surface, is provided. This method comprises the steps of applying a treatment solution comprising a fatty acid compound, an alkalizing agent, and a solvent comprising water and from about 5% to about 90% by volume of an organic solvent selected from the group consisting of an alcohol, a glycol ether, and combinations thereof to the surface; and then removing substantially all of the solvent from the solution to provide a thin film on the surface of said substrate. The film comprises the fatty acids that were present in the treatment solution. In a preferred embodiment the treatment solution further comprises a chelating agent. The present invention also relates to a treatment solution for reducing adhesive resin bleed on the surface of a circuitized organic substrate. The present invention also relates to a circuitized organic substrate that is resistant to resin bleed. Such substrate has a film comprising a fatty acid compound disposed on the circuitized surface thereto.
