JPH10173121A - Leads for surface mount components - Google Patents

Abstract

(57) [Problem] The present invention relates to a lead of a surface mount component which is small, lightweight, thin and capable of supporting high-density mounting, and has an effect of improving the productivity and reliability of a printed circuit board. Realize the lead of surface mount components. According to the present invention, a lead of a surface mount component having a lead for connection with a footprint of a printed wiring board is formed of a shape memory alloy. By this means, the footprint of the printed wiring board and the lead of the surface mount component are accurately positioned and brought into contact by utilizing the pressing force of the lead of the surface mount component without providing a step of correcting the lead. Therefore, there is provided a lead of a surface mount component which enables all leads to be closely connected in correspondence with the non-planarity of a printed wiring board.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applicable to a high-density mounting that can effectively utilize both sides of a printed wiring board, reducing the floating capacitor and unnecessary inductance of a lead, which have been demanded for electric and electronic parts. And
In order to be able to support automatic supply and automatic assembly, and to contribute to the improvement of the wiring density of printed wiring boards by eliminating holes for leads, we have responded to small, light, thin and highly functional. The present invention relates to the realization of the lead of the surface mount component, which is related to the lead of the surface mount component and has the effect of improving the productivity and reliability of the printed circuit board.

[0002]

2. Description of the Related Art The lead (52) of a surface mount component (51) in the conventional example shown in FIG. 4 tends to increase in the number of leads of the surface mount component due to the enhancement of the function of the surface mount component (51). At the same time, the miniaturization of leads is progressing. Therefore, the lead (52) of the surface mount component (51) is accompanied by a decrease in physical strength. As a result, the lead (52) is easily deformed by an external force in the manufacturing process as the surface mount component (51), during transportation and storage, and in the manufacturing process as a printed circuit board, and the surface mount component (51) is printed as it is by reflow. When connected to the wiring board (53), the bent leads tend to cause a short circuit with an adjacent circuit and the raised leads tend to cause incomplete connection or the like. Unless any corrective measures are taken, the manufacturability and reliability of the printed circuit board are reduced. Has the problem of adversely affecting

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to solve the following problems of the above-mentioned lead of the conventional surface mount component. As the functions of surface-mounted components have become more sophisticated, the number of leads of surface-mounted components has tended to increase, and at the same time, the miniaturization of leads has been progressing. Therefore, the lead of the surface mount component is accompanied by a decrease in physical strength. As a result, the lead is easily deformed by external force during the manufacturing process, transport and storage of the surface mounted component itself, and also during the manufacturing process as a printed circuit board, and the printed wiring is reflowed as it is without taking any corrective measures When the connection with the board is made, defects such as short-circuit and incomplete connection are likely to occur, which adversely affects the manufacturability and reliability of the printed circuit board.

[0004]

According to the present invention, in order to solve the above-mentioned problems, the lead of a surface mount component having a lead for connection with a footprint of a printed wiring board is formed of a shape memory alloy. By this means, the lead of the surface mount component having a lead for connection with the footprint of the printed wiring board is changed to a predetermined accurate shape at a predetermined temperature without providing a step of correcting the lead. Since the footprint of the printed wiring board and the lead of the surface-mounted component can be accurately positioned, or the footprint of the wiring board can be brought into contact with the lead of the surface-mounted component using pressing force, Position of the printed circuit board and the lead of the surface-mounted component are accurately positioned, and the pressing force is applied to the footprint of the printed wiring board and the lead of the surface-mounted component centering on the adhesive used to fix the surface-mounted component. To provide surface mount component leads that enable all leads to be closely connected in response to the non-planarity of the printed wiring board surface

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, according to a first aspect of the present invention, as shown in FIG. 1, a lead 2 of a surface mount component 3 having a lead 2 is connected to a footprint 1 of a printed wiring board. And a shape memory alloy. By this means, it is ideal for surface mounting in which the lead of the surface mount component having the lead for connection with the footprint of the printed wiring board is stored at a predetermined temperature or higher without providing a step for correcting the lead. Restore the shape and accurately position the printed wiring board footprint and the surface mount component leads, or use the pressing force to make close contact between the printed wiring board footprint and the surface mount component leads. Therefore, the footprint of the printed wiring board and the lead of the surface mount component are accurately positioned, and the footprint of the printed wiring board and the surface mount component are centered on the adhesive used to fix the surface mount component in advance. Of the printed wiring board surface due to the suspension action of the pressing force. That.

Next, in a second aspect of the present invention,
As shown in FIG. 2, the lead 2 was made of a shape memory alloy whose transformation temperature was a preheating temperature in a preheating step in a series of steps of connecting to a printed wiring board by reflow.
By this means, the lead of the surface mount component having the lead in connection with the footprint of the printed wiring board was stored with the transformation temperature set to the same as the preheating temperature, without providing a step of particularly correcting the lead. Connect the printed wiring board footprint and the surface mount component leads to the printed wiring board by reflow by reflowing so that the shape can be restored to the correct shape. The footprint of the printed circuit board and the lead of the surface-mounted component can be brought into close contact with each other using the pressing force, so that the footprint of the printed wiring board and the lead of the surface-mounted component are accurately positioned, and the surface-mounted component is previously determined. Pressing force is applied to the printed circuit board footprint and the surface mount component leads, centering on the adhesive used to fix the Obtaining an effect that makes it possible to adhere connected that corresponds to the non-planarity of the printed circuit board surface with the suspension action.

[0007] In a third aspect of the present invention,
As shown in FIG. 3, a part in which a preheating temperature in a preheating step in a series of steps of connecting the lead 2 to a printed wiring board by reflow is a transformation temperature, and a main temperature higher than the preheating temperature after the preheating step. And a portion where the reflow temperature in the connection step is the transformation temperature. By this means, the lead of the surface mount component having the lead for connection with the footprint of the printed wiring board is stored in the part where the transformation temperature is set to the same as the preheat temperature, without providing a step for correcting the lead in particular. The printed circuit board's footprint and the leads of the surface mount components are accurately positioned during preheating, and then the printed circuit board is set at the same transformation temperature as the reflow temperature. The contact between the footprint of the printed circuit board and the lead of the surface-mounted component can be brought into close contact by generating a pressing force, so that after accurately positioning the footprint of the printed wiring board and the lead of the surface-mounted component, fixing the surface-mounted component To the pressure generated by the printed circuit board footprint and the surface mount component leads, centered on the adhesive used for Obtain the advantageous also possible to adhere connected that corresponds to the non-planarity of the printed circuit board surface with the suspension action.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention; FIG.

Reference numerals used in the drawings of the embodiments of the present invention shown in FIGS. 1 to 3 will be collectively described below. 1
Is a footprint formed on a printed wiring board for connecting a surface mount component to the printed wiring board. Reference numeral 2 denotes a lead for connecting the surface-mounted component to the printed wiring board and configured as a surface-mounted component. Reference numeral 3 denotes a surface mount component for making electrical connection with a footprint formed on a printed wiring board without using a component hole. Reference numeral 5 denotes an adhesive for fixing the surface mount component 3 to the printed wiring board.

FIGS. 1A and 1B are diagrams showing the principle of the present invention, wherein FIG. 1A shows a state before mounting and FIG. 1B shows a state after mounting. In the figure, a lead 2 of a surface mount component 3 having a lead 2 for connection with a footprint 1 of a printed wiring board is stored at a predetermined temperature, which is a transformation temperature, in an ideal shape for a predetermined surface mounting. It was made of a shape memory alloy made of a TiNi alloy or the like that restored to a shape ideal for surface mounting stored at a predetermined transformation temperature or higher at a predetermined memory. This makes it possible to align the leads of surface-mounted components that have leads for connection to the footprint of the printed wiring board at a certain transformation temperature or higher without the need for a special step of straightening the leads. The tip that obtains the shape or suspension effect is restored to an obtuse lead bending state, and the printed circuit board footprint and the surface mount component lead are accurately positioned, or the printed circuit board footprint and the surface mount component lead. Can be brought into close contact using the pressing force, so that the footprint of the printed wiring board and the lead of the surface mount
In addition to accurate positioning, the printed wiring board surface becomes non-planar due to the suspension of the printed wiring board footprint and the surface mounted component leads by pressing force, centering on the adhesive used to fix the surface mounted components in advance. Corresponding close contact can be achieved.

FIG. 2 is a diagram showing a first embodiment of the present invention.
(A) shows before mounting and (b) shows after preheating. In the figure, the lead 2 is made of a shape memory alloy whose transformation temperature is a preheating temperature in a preheating step in a series of steps of connecting to a printed wiring board by reflow. As a result, the lead of the surface mount component having the lead for connection with the footprint of the printed wiring board was stored with the transformation temperature set to the same as the preheating temperature, without providing a step for correcting the lead in particular. A series of series that connects the footprint of the printed wiring board and the lead of the surface-mounted component to the printed wiring board by reflow, by restoring the lead refraction state where the tip that obtains the ideal lead alignment shape or suspension action for surface mounting is obtuse, and reflows. Since the positioning can be performed accurately after preheating before the main connection step in the process, or the footprint of the printed wiring board and the lead of the surface mount component can be brought into close contact using the pressing force, the printed wiring board Precise positioning of the footprint and the lead of the surface mount component and surface mounting before the preheating process Adhesive can be adhered correspondingly connected to the footprint surface mount component leads of the printed wiring board in a non-planarity of the printed circuit board surface with the suspension effect of the pressing force around the used for fixing the goods.

FIG. 3 is a diagram showing a second embodiment of the present invention.
(A) shows the state before mounting, (b) shows the state after preheating, and (c) shows the state after mounting. In the figure, a part where the preheating temperature of a preheating step in a series of steps of connecting the lead 2 to the printed wiring board by reflow is a transformation temperature is defined as the entire lead,
The portion where the reflow temperature in the main connection step, which is higher than the preheating temperature after the preheating step, is used as the transformation temperature was used as the contact portion 6 with the footprint of the tip of the lead. As a result, there is no need to provide a step for correcting the lead,
The lead of the surface mount component that has a lead for connection to the footprint of the printed wiring board is restored to the ideal lead alignment shape for surface mounting that first stores the entire lead in the part where the transformation temperature is set to the same as the preheat temperature So that the footprint of the printed wiring board and the lead of the surface mount component are accurately positioned at the time of preheating, and then the refraction state is set to the same transformation temperature as the reflow temperature. By forming the contact portion in a downwardly tapered form, the footprint of the printed wiring board can be brought into close contact with the downwardly bent bent lead that obtains the suspension action of the surface mount component by generating a pressing force, After accurately positioning the printed circuit board footprint and the surface mount component leads in the preheating process, Supports the non-planarity of the surface of the printed wiring board by the pressing action that generates the footprint of the printed wiring board and the lead of the surface mounted component centering on the adhesive used to fix the surface mounted component before the preheating process And tightly connected.

The part where the preheat temperature is the transformation temperature and the part where the reflow temperature is the transformation temperature are determined depending on the manufacturing process as a surface-mounted component, transportation and storage, and the status of the manufacturing process as a printed circuit board. The same effect may be obtained for each lead row or each lead.

[0014]

The effects of the present invention described above will be described in the order of claims.

According to the first aspect of the present invention, the lead of the surface mount component having a lead for connection with the footprint of the printed wiring board is formed of a shape memory alloy. This makes it ideal for surface mounting in which the leads of surface mount components that have leads for connection to the footprint of a printed wiring board are stored at a predetermined temperature or higher without providing a process for correcting the leads. Restore the shape and accurately position the printed wiring board footprint and the surface mount component leads, or use the pressing force to make close contact between the printed wiring board footprint and the surface mount component leads. Therefore, the footprint of the printed wiring board and the lead of the surface mount component are accurately positioned, and the footprint of the printed wiring board and the surface mount component are centered on the adhesive used to fix the surface mount component in advance. Can be tightly connected to the non-planarity of the surface of the printed wiring board by the suspension action of the pressing force, and the surface mount Defects such as short circuit or connection incomplete connection between the printed circuit board is less likely to occur due to low, improving the manufacturability of the printed circuit board and reliability can be improved.

The lead of the surface-mounted component having the structure described in claim 2 is formed of a shape memory alloy whose transformation temperature is a preheating temperature in a preheating step when the lead is connected to a printed wiring board by reflow. With this, the correction of the lead is automatically performed after the preheating before the main connection step in a series of steps of connecting the footprint of the printed wiring board and the lead of the surface mount component to the printed wiring board by reflow, Since the positioning can be performed accurately or the footprint of the printed wiring board and the lead of the surface-mounted component can be brought into close contact using the pressing force, the effect described in claim 1 can be obtained. The timing and the change when the shape is restored to the ideal shape become stable.

The lead of the surface mount component having the configuration according to claim 3 is a part in which a preheating temperature in a preheating step when the lead is connected to a printed wiring board by reflow is a transformation temperature and a reflow in a main connection step. And a part where the temperature is the transformation temperature. With this, the lead of the surface mount component having a lead for connection with the footprint of the printed wiring board is first restored to the lead alignment shape stored in the entire lead of the portion where the transformation temperature is set to the same as the preheating temperature. Then, the printed circuit board footprint and the surface mount component leads are accurately positioned at the time of preheating, and then the contact portion of the refracted lead tip footprint in the portion where the transformation temperature is set to the same as the reflow temperature In addition to the effect described in claim 1, the footprint of the printed wiring board can be brought into close contact with the lead in a downwardly bent state that obtains a suspending action of the surface-mounted component by pressing force. After accurately positioning the footprint of the printed wiring board and the lead of the surface mount component in the process, the main connection process The two-step automatic connection of the footprint of the printed wiring board and the lead of the surface mount component to the non-planarity of the surface of the printed wiring board by the suspension action by the pressing force, centering on the adhesive used for the fixed The timing and the change of the stored shape that is ideal for surface mounting are more stable.

[Brief description of the drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a diagram of a first embodiment of the present invention.

FIG. 3 is a diagram of a second embodiment of the present invention.

FIG. 4 is an embodiment diagram of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Footprint 2 Lead 3 Surface mount component 5 Adhesive

Claims (3)

[Claims] A printed circuit board footprint (1)
A lead (2) of the surface mount component (3) having a lead (2) for connection with the lead (2) is made of a shape memory alloy. 2. The surface mount component according to claim 1, wherein the lead is made of a shape memory alloy whose transformation temperature is a preheating temperature when the lead is connected to a printed wiring board by reflow. Lead. 3. A lead (2) comprising a portion having a transformation temperature at a preheating temperature when connecting to a printed wiring board by reflow and a portion having a transformation temperature at a reflow temperature. Item 4. A lead of the surface mount component according to Item 1.