Surface mount assembly for electronic components

Details Surface mount assembly for electronic components Surface mount assembly for electronic components

1998-11-05

2001-10-30

Gandhi, Jayprakash N. (Department: 2841)

Electricity: electrical systems and devices

Housing or mounting assemblies with diverse electrical...

For electronic systems and devices

C361S760000, C361S767000, C361S807000, C174S260000, C174S263000, C228S165000

Reexamination Certificate

active

06310780

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a surface mount assembly for electronic components and, more particularly, to a surface mount assembly for electronic components with the supply of solder paste by using a screen printing.
Conventional methods of mounting electronic components on a substrate involve placing a metal mask on a smooth, flat surface of the substrate. Solder paste is screened into openings in the metal mask as solder portions for the subsequent mounting of electronic components on the substrate. Some of the electronic components require a relatively large amount of solder paste while others don't. In the case that the electronic components require the large amount of solder paste, the solder portions are required to have a relatively large size in thickness. However, the screen printing conventionally used is not adapted to supply different amounts of solder paste for different components.
Japanese Patent Laid-Open No. 62-181494 discloses a method of mounting electronic components on a substrate that overcomes the above-mentioned problem. This method employs two masks: a first mask having large windows for supplying a larger amount of solder paste as well as small windows for a smaller amount of solder paste and a second mask having large windows for supplying a larger amount of solder paste. The solder paste is supplied onto the substrate by using the first mask and then the second mask overlapped with the first mask on the top surface thereof. This approach is hereinafter referred to as a first prior art.
There is another method that overcomes the above-mentioned problem in which a plurality of openings are formed in a metal mask for screen printing at the position corresponding to the electronic components to be mounted on a substrate. The openings are varied in diameter for supplying different amounts of solder paste to the substrate for the different electronic components. This approach is hereinafter referred to as a second prior art.
The first prior art requires two or more masks depending on the desired amount of the solder paste for the different electronic components. On the other hand, the second prior art requires the metal mask to have a uniform thickness because the amount of the solder paste to be supplied on the substrate is determined according to the difference in diameter. Thus, the amount of the solder paste in the openings would be suitable for one or some of the electronic components and may not be good for the remainders. Since solder paste spread away in the openings, the difference in diameter is not a sufficient factor for precise control of the amount of the solder paste in the openings.
Furthermore, since conventional substrates have a uniform thickness, a connector cannot be attached to a side of the substrate when the thickness exceeds a certain limit.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a surface mount assembly on which electronic components are mounted on solder portions of various amounts on a substrate that are desirable for individual components.
Another object of the present invention is to provide a substrate suitable for the above-mentioned surface mount assembly for electronic components.
It is yet another object of the present invention to provide a method of mounting electronic components as the above-mentioned surface mount assembly for electronic components.
It is still another object of the present invention to provide a surface mount assembly for electronic components in which a thickness of a substrate is not a limitation to the choices of a connector to be attached to a side of the substrate.
A surface mount assembly for electronic components according to a first invention comprises a substrate on which an electronic component is to be mounted; an indentation formed in one major surface of the substrate; electrode pads provided on the bottom of the indentation; solder portions provided on the respective electrode pads; and an electronic component having a plurality of terminals. The terminals of the electronic component are connected to the corresponding electrode pads with the solder portions.
A surface mount assembly for electronic components according to a second invention comprises a substrate on which electronic components are to be mounted; indentations formed in one major surface of the substrate for the respective electronic components; electrode pads provided on the bottom of each indentation; solder portions provided on the respective electrode pads; and electronic components each having a plurality of terminals. The electronic components correspond to the indentations. The terminals of the individual electronic components are connected to the corresponding electrode pads with the solder portions.
A surface mount assembly for electronic components according to a third invention comprises a substrate having at least one electronic component mounted thereon; a notch formed in one major surface of the substrate along the perimeter thereof; a first electrode pad provided on the bottom of the notch; a second electrode pad provided on another major surface opposing to the one major surface of the substrate at the position corresponding to the first electrode pad; and an electronic component having first and second terminals connected to the first and the second electrode pads, respectively.
The substrate according to the present invention has a component mount area on which an electronic component is to be mounted. The substrate has an indentation formed in the component mount area on at least one major surface. The indentation has a dimension determined depending on a size of the electronic component to be mounted.
A method of mounting electronic components on a substrate is applicable to mount electronic components each having a plurality of terminals on a substrate having indentations formed in one major surface thereof and electrode pads provided on the bottom of each indentation.
The method of mounting electronic components on the substrate according to an aspect of the present invention comprises the steps of: placing on the substrate a metal mask having a plurality of openings formed at the positions corresponding to the electrode pads; supplying solder paste to the electrode pads through the openings in the metal mask and then removing the metal mask; mounting the electronic components on the substrate such that the terminals of the components correspond to the respective electrode pads in the corresponding indentations; and melting the solder paste to connect the terminals of the electronic components with the electrode pads.


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