JPH0354899A - Mounting structure for electronic component onto printed wiring board - Google Patents

Abstract

PURPOSE:To easily mount an electronic component on a printed wiring board by interposing a conductive material having elasticity between the component and the board, and forming of a shape memory alloy a mounting piece protruding from the component to the board. CONSTITUTION:Leads 12 of conductive rubber protrudes from the lower surface of a semiconductor package 11 to a printed wiring board 2 to lead the signals of semiconductor chips to lands 4. Leads used also as mounting pieces 13 of shape memory alloy protrude to the board 2 at four corners of the package 11. The piece 13 becomes linear except at ambient temperature, and a L shape at the ambient temperature. The length of the lead 12 is shorter than the length H1 of the piece 12 except at the ambient temperature and slightly longer than H2 at the ambient temperature. The end 12a of the lead is opposed to the land 4 in an enviroment except the ambient temperature, and the end 13a of the piece 13 is soldered to a predetermined land 4. When it is returned to the ambient temperature, the piece 13 is bent in a L shape, the end 12a of the lead is brought into pressure contact with the land 4 to be electrically connected. The L-shaped part A absorbs a distortion to be accurately mounted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a structure for mounting electronic components on a printed wiring board.

[Prior Art] A conventional mounting structure of electronic components on a printed wiring board is shown in FIG.

In the figure, l is a semiconductor package as an electronic component mounted with a semiconductor chip, 2 is a printed wiring board, and 3 is below the F surface 1a of the semiconductor package 1 (in the direction of the printed wiring board 2).
4 is a land formed on the printed wiring board 2; 5 is a solder for joining the tip 3a of the lead 3 and the land 4; .

By bonding the tips 38 of the leads 3 of the first semiconductor package to the lands 4 with solder 5, the semiconductor package can be electrically and mechanically attached to the printed wiring board 2. Note that a technique such as a beam flow method is used for the soldering described above.

[Problems to be Solved by the Invention] However, according to the above-mentioned conventional mounting structure for electronic components on a printed wiring board, solder bonding occurs due to the difference in thermal expansion coefficient between the semiconductor package 1 and the printed wiring board 2. In order to absorb the distortion in the parts, the leads 3 had to be designed with a multilayer structure, and also in the soldering technology,
There were problems such as the need for highly accurate temperature control in order to achieve good solder bonding between the lead 3 and the land 4 at the center of the semiconductor package 1.

The present invention has been made to solve the above-mentioned problems, and aims to provide a mounting structure for electronic components on a printed wiring board that allows electronic components to be mounted accurately and easily.

[Means for Solving the Problems] The structure for mounting electronic components on a printed wiring board according to the present invention includes interposing an elastic conductive material between the electronic component and the land of the printed wiring board, and interposing the conductive material through the conductive material. At the same time, the tips of a plurality of mounting pieces protruding from the electronic component toward the printed wiring board are fixed to the printed wiring board, and the mounting pieces are bent at room temperature and are not exposed to temperatures other than room temperature. It is made of a shape memory alloy that becomes a straight line.

[Operation] The mounting piece made of a shape memory alloy is memorized so that it maintains a straight shape at temperatures other than room temperature, but bends at room temperature. First, the mounting piece is soldered to the land with the tip of the lead of the electronic component facing the land in an environment other than room temperature.

When the temperature reaches room temperature in this state, the mounting piece bends into the memorized shape, so that the tip of the lead and the land come into pressure contact, and the electronic component is electrically connected to the printed wiring board.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described based on the drawings 1 and 2. Incidentally, the same parts as in the conventional example shown in FIG. 4 are given the same reference numerals, and the explanation thereof will be omitted.

In each episode, 11 is a semiconductor package as an electronic component mounted with a semiconductor chip according to the present invention, and 12 is a part below i1La of the semiconductor package 11 (printed wiring board 2
13 is a lead from conductive rubber that protrudes in the direction of the semiconductor package 1 and leads the signal of the semiconductor chip to the land 4.
1 is a mounting piece made of a shape memory alloy that protrudes downward from the four corners of the lower part 11a (in the direction of the printed wiring board 2), and serves as a reed as shown in Fig. 1 at temperatures other than room temperature. In this case, the shape is memorized so that it becomes a ``<'' shape as shown in FIG. The length of the lead 12 is the length H1 of the mounting piece 12 at temperatures other than room temperature.
It is set to be shorter than , and slightly longer than the length H2 of the mounting piece ↓2 at room temperature.

With the above configuration, first, in an environment other than room temperature, with the tips 12a of the leads 12 of the semiconductor package 11 facing the lands 4, the tips 13a of the mounting pieces 13 are soldered to the predetermined lands 4.

When the temperature reaches room temperature in this state, the mounting piece l3 bends into the memorized dogleg shape as shown in Fig. 2, and the tip 12a of the lead 12 and the land 4 come into pressure contact, creating an electrical connection. will be done.

According to this embodiment, the semiconductor package 11 can be easily mounted on the printed wiring board 2 by simply soldering the mounting pieces 13 to the lands 4. Also, at the solder joint between the mounting piece 13 and the land 4, the mounting piece 13
By bending in the shape of tp < u, this P
I (Since the 71-shaped portion A absorbs distortion due to the difference in thermal expansion coefficient between the semiconductor package 11 and the printed wiring board 2, no distortion occurs in the solder joint, and accurate mounting can be performed.

According to the above embodiment, each lead 12 is made of conductive rubber, but anisotropically conductive rubber, that is, the third
As shown in the figure, conductive powder is added to a sheet of conductive rubber,
An anisotropically conductive rubber sheet 14 is provided with a conductive layer S extending from the terminal 15 of the semiconductor package 11 in the land 4 direction.
All signals may be connected on one sheet using .

Further, the lead 12 is not made of conductive rubber, but may be made of a metal lead having spring properties such as phosphor bronze.

Further, the mounting piece 3 may not also serve as a lead, but may be used exclusively for fixing, and may be fixed with adhesive instead of solder.

Furthermore, although the leads 12 are formed of conductive rubber, they may be formed of an ordinary conductive material, and the conductive rubber may be attached to the lands 4.

Further, in the above embodiment, the mounting pieces 13 are provided at the four corners of the lower part 11a of the semiconductor package t1, but several pieces may be provided from the periphery of the lower surface 11a.

[Effects of the Invention] As explained above, according to the structure for mounting electronic components on a printed wiring board according to the present invention, an elastic conductive material is interposed between the electronic component and the land of the printed wiring board. In addition to guiding the signals of electronic components to the land via the conductive material,
The tips of a plurality of mounting pieces protruding from the electronic component toward the printed wiring board are fixed to the printed wiring board, and the mounting pieces are
Because it is made of a shape memory alloy that bends at room temperature and straightens at temperatures other than room temperature, electronic components can be easily and accurately mounted.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams showing one embodiment of the structure for mounting electronic components on a printed wiring board according to the present invention, FIG. 3 is a diagram showing another embodiment of the present invention, and FIG. 4 is a conventional FIG. 2 is a diagram showing an example of a mounting structure of electronic components on a printed wiring board. 2... Printed wiring board, 4... Land, 11... Semiconductor package (electronic component), 12... Lead made of conductive rubber (elastic conductive material), 13... Shape memory alloy A mounting piece (mounting piece) that also serves as a certain lead.

Claims (1)

[Claims] A conductive material having elasticity is interposed between the electronic component and the land of the printed wiring board, and a signal from the electronic component is guided to the land via the conductive material. The tip of the mounting piece is fixed to the printed wiring board, and the mounting piece is made of a shape memory alloy that is bent at room temperature and straight at temperatures other than room temperature. Implementation structure.