EP0430240A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Method of mounting an electric part on a circuit board
Assignee: Furukawa Electric Co Ltd
•
Filing: 1990-11-29
•
Granted: —
•
Expires: 2010-11-29
Abstract
Abstract 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 composition is heated so as to cause precipitation, thereby forming a solder layer formed of an Sn-Pb alloy substantially only on 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 to be 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 with the pads.
Inventors
- 👤 Kenichi Fuse
- 👤 Takao Fukunaga
- 👤 Masanao Kohno
- 👤 Hisao Irie
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 19:07
CPC Classifications
H; H05; H05K; H05K3/00; H05K3/30; H05K3/32; H05K3/34; H05K3/3465; H05K3/3485; B; B23; B23K; B23K35/00; B23K35/22; B23K35/34; H05K2201/00; H05K2201/10; H05K2201/10613; H05K2201/10954; H05K2201/10992; H05K2203/00; H05K2203/04; H05K2203/043; H05K2203/12; H05K2203/125; H05K3/3473
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
105 words
A method of forming a solder layer on pads of a circuit board, comprising the steps of: applying a paste-like composition containing a lead salt of an organic acid and tin powder on a pad array portion on the circuit board; and heating the composition to cause a solder precipitation, thereby forming solder layers formed of an Sn-Pb alloy substantially only on pads, said solder precipitation for forming a solder alloy being 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.
Claim 2
Dependent Claim
31 words
A method of forming a solder layer on pads of a circuit board according to claim 1, characterized in that said solder layers contain an Sn-Pb alloy having Pb rich composition.
Claim 3
Independent Claim
87 words
A method of mounting electronic parts on a circuit board, comprising the steps of: forming preparatory solder layers formed of an Sn-Pb alloy substantially only on pads of a pad array portion on the circuit board; applying a paste-like composition containing a lead salt of an organic acid and tin powder on the preparatory solder layers; putting an electronic part on the paste-like composition; and heating the composition to cause solder precipitation for forming a solder alloy, thereby soldering the pads with leads of the electronic part.
Claim 4
Dependent Claim
41 words
A method according to claim 3, characterized in that said preparatory solder layers are formed by applying a paste-like composition containing a lead salt of an organic acid and tin powder on the pad array portion, and heating the paste-like composition.
Claim 5
Dependent Claim
18 words
A method according to claim 3, characterized in that said preparatory solder layers are formed by electroless plating.
Claim 6
Dependent Claim
46 words
A method according to claim 3, characterized in that said solder 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.
Claim 7
Dependent Claim
20 words
A method according to claim 3, characterized in that said solder alloy contains an Sn-Pb alloy having Pb rich composition.
Claim 8
Independent Claim
96 words
A method of mounting an electronic part on a circuit board, comprising the steps of: forming preparatory solder layers formed of an Sn-Pb alloy substantially only on pads of a pad array portion of the circuit board; applying a paste-like composition containing a lead salt of an organic acid and tin powder to leads of an electronic part to be soldered with the pads; putting the electronic part on the preparatory solder layers; and heating the composition to cause solder precipitation for forming a solder alloy, thereby soldering the pads with leads of the electronic part.
Claim 9
Dependent Claim
40 words
A method according to claim 8, characterized in that said preparatory solder layers are formed by applying a paste-like composition containing a lead salt of an organic acid and tin powder on the pad array, and heating the paste-like composition.
Claim 10
Dependent Claim
18 words
A method according to claim 8, characterized in that said preparatory solder layer is formed by electroless plating.
Claim 11
Dependent Claim
46 words
A method according to claim 8, characterized in that said solder 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.
Claim 12
Dependent Claim
20 words
A method according to claim 8, characterized in that said solder alloy contains an Sn-Pb alloy having Pb rich composition.
Claim 13
Independent Claim
136 words
A method of mounting an electronic part on a circuit board, comprising the steps of: forming preparatory solder layers formed of an Sn-Pb alloy substantially only on pads of a pad array portion on the circuit board; applying a paste-like composition containing a lead salt of an organic acid and tin powder to leads of an electronic part to be soldered with the pads; heating the paste-like composition to cause solder precipitation for forming preparatory solder layers on the leads; applying a flux at least one of the preparatory solder layers on the pads and the preparatory solders layer on the leads; putting the electronic part on the preparatory solder layer on the pads; and heating the preparatory solder layers on the pads and the leads, thereby soldering the pads with leads of the electronic part.
Claim 14
Dependent Claim
39 words
A method according to claim 13, characterized in that said preparatory solder layers on the pads are formed by applying a paste-like composition containing a lead salt of an organic acid and tin powder, and heating the paste-like composition.
Claim 15
Dependent Claim
21 words
A method according to claim 13, characterized in that said preparatory solder layers on the pads are formed by electroless plating.
Claim 16
Dependent Claim
46 words
A method according to claim 13, characterized in that said solder 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.
Claim 17
Dependent Claim
20 words
A method according to claim 13, characterized in that said solder alloy contains an Sn-Pb alloy having Pb rich composition.
Claim 18
Independent Claim
118 words
A method of mounting an electronic part on a circuit board, comprising the steps of: applying a paste-like composition containing a lead salt of an organic acid and tin powder on a pad array portion on the circuit board; heating the paste-like composition to cause solder precipitation, thereby forming solder layers formed of an Sn-Pb alloy by an amount required for mounting an electronic part on pads of the pad array portion; applying a flux at least one of the solder layer and leads of an electronic part which is to be mounted on the pads; putting the electronic part on the pads; and heating the solder layers and soldering the pads with leads of the electronic part.
Claim 19
Dependent Claim
46 words
A method according to claim 18, characterized in that said solder 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.
Claim 20
Dependent Claim
16 words
A method according to claim 18, characterized in that said flux is of a non-halogen type.
Claim 21
Dependent Claim
20 words
A method according to claim 18, characterized in that said solder alloy contains an Sn-Pb alloy having Pb rich composition.
Claim 22
Dependent Claim
43 words
A method according to claim 18, characterized by further comprising the step of applying pressure to the upper surfaces of the solder layers, after the step of forming the solder layers, and before the step of putting an electronic part on the pads.
Claim 23
Dependent Claim
25 words
A method according to claim 22, characterized in that pressure is applied to the upper surfaces of the solder layers while heating the solder layer.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.