Harima Chemicals, Incorporated

The Furukawa Electric Co., Ltd.

Hisao Irie

Takao Fukunaga

Kenichi Fuse

Kazuki Ikeda

Masanao Kono

Takaaki Anada

Masanao Kohno

Hiroshi Tanaka

Keigo Obata

Takao Takeuchi

Kenzo Kobayashi

Hirokazu Shiroishi

Yasutaka Nishi

Shinsuke Ohara

Seishi Kumamoto

Yoshihiro Hasegawa

Tatsuji Mizuta

Ryo Inoue

Naoya Inoue

Izumi Kosuga

Syunsuke Ishikawa

Eiichiro Matsubara

Hisao Nakajima

Tetsu Ichitsubo

Toshinori Shima

A flux for soldering used when soldering is performed to a board subjected to electroless nickel plating, the flux containing resin having film forming ability, activator, and solvent, and further containing metallic salt in an amount of 0.1 to 20% by weight of the total amount of flux. The use of this flux suppresses diffusion of nickel solder in soldering portions, and prevents concentration of phosphorous, thereby improving the bonding strength of soldering.

Flux for soldering, soldering method, and printed circuit board

The present invention is a method to manufacture the SnZnNiCu solder powder through liquid quenching atomizing method, and an atomizing temperature is not less than 500&#xb0; C., in particular, not less than 900&#xb0; C. The raw material metal used as raw material of the solder powder comprises 3 to 12% by weight of Zn, 1.0 to 15% by weight of the sum of Cu and Ni, and Sn and inevitable impurities for the rest, to the total amount of raw material. Thereby, high joint strength is achieved and the SnZnNiCu solder powder which can improve joint reliability of solder joint part is provided.

Method of manufacturing the SnZnNiCu solder powder and the SnZnNiCu solder powder

According to present invention, there is provided a lead-free solder precipitating composition comprising a tin powder, and a complex of silver ions and/or copper ions and aryl phosphines, alkyl phosphine, phosphines or azoles. The solder precipitating composition can form proper lead-free solder on lands of a circuit board, without forming silver and/or copper film on the circuit board.

Solder precipitating composition

A plurality of pads are formed on a circuit board body at a pitch of 0.5 mm or less. The pads are formed such that a projecting height H of a pad from the board body surface and a width W of the pad satisfy a relation 2H&lt;W, that a pad array is formed in which a width of each of the pads located at two ends of the pad array is larger than that of a pad located therebetween, and that the pad width W and a pad-to-pad distance D satisfy a relation W&gt;D. A solder layer, obtained by a substitution reaction between a powder of a metal having the highest ionization tendency among metals constituting the solder layer or a powder of an alloy thereof and a salt formed by bonding the other metal or metals in the solder layer to an organic acid, is formed on each pad.

Solder-coated printed circuit board and method of manufacturing the same

A solder precipitating composition comprises a powder of a metal having the highest ionization level among metals constituting a solder alloy to be prepared, and a salt between a carboxylic acid and a remaining metal of the solder alloy. The composition is applied to a surface on which the solder is to be precipitated, and the solder is precipitated, thereby performing soldering.

A paste-like composition containing a lead salt of an organic acid and tin powder is applied on a pad array portion of a circuit board. Then, the paste-like compsition is heated so as to cause precipitation, thereby forming a solder layer formed of a Sn-Pb alloy substantially only on the pads. This precipitation is performed in a state that a liquid pool is formed on the pad array portion when the paste-like composition is liquefied by heating, and the tin powder is settled in the liquid pool. When an electronic part is mounted on the pads, first, preparatory solder layers are formed on the pads by the above-mentioned precipitation process. After a paste-like composition is applied on the preparatory solder layers, the electronic part is put on the paste-like composition. Then, the paste-like composition is heated, thereby soldering leads of the electronic part to the pads.

Method of forming a solder layer on pads of a circuit board and method

A method for forming a metal film on the surface of a substrate metal, which comprises soaking a substrate metal or a non-metal support carrying the substrate metal thereon in a solution of a metal salt in a high boiling point solvent under heating conditions, characterized in that the metal salt is a salt of the metal to be formed on the surface of the substrate metal with an acidic substance selected from an organic carboxylic acid, a rosin and a rosin derivative. The metal is precipitated from the solution exclusively on the surface of the substrate metal without forming any solid metal particle in the solution or on the substrate metal. Thus, the method is applicable to the formation of a soldering alloy as a film on the surface of a substrate metal without leaving thereon any free metal particle which may cause short circuits in electronic circuits. The method can thus be applied advantageously to the manufacture of electronic elements having a metal film thereon and high density printed circuits, and thus is also useful in the field of electronic industry.

Method for forming a metal film on the surface of a substrate metal

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Takasago, Japan

Hisao Irie