JPH0352290A - Soldering - Google Patents

Abstract

PURPOSE:To enhance the temporary fixing strength of cream solder and prevent the occurrence of misregistration of surface mounting components, by applying the cream solder to the lead sections of the surface mounting components to be soldered in a steplike shape so that the solder may be thin at the tip sections of the leads and thick at the root sections. CONSTITUTION:Cream solder 2 is applied to the lead sections 5a of a surface mounting component 5 to be soldered in a steplike shape so that the solder 2 may be thin at the tip sections of the leads 5a and thick at the root sections. The steplike print shape of the cream solder 2a like this makes it possible to fix a surface mounting component 5 with leads having inclined lead sections 5b securely on the cream solder 2a temporarily. Accordingly, the occurrence of misregistration is prevented even against vibration which may occur in time of mounting other components or in time of moving to a reflow furnace, and excellent reflow soldering can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention J (Field of Industrial Application) The present invention relates to a soldering method, and particularly to a method for soldering electronic components onto a substrate.

(Prior art) Conventionally, in order to solder surface mount components onto a board using the reflow soldering method, cream solder printing, component mounting,
It is generally known that mounting is performed in the order of reflow soldering. As shown in Figures 5 and 6, the cream is dried.
In Ill printing, cream solder 2 is placed on a thin flat mask 1 in which slits 1a are formed, and a flat squeegee 3 is moved while pressing against the mask 1, thereby forming the slits 1a in the mask 1. 1a with cream solder 2
a passes through, and cream solder 2a is printed in the shape of the slit 1a on the soldering location 4a of the board 4. At this time, since the thickness of the mask 1 is constant, the thickness of the cream solder 2a printed on the substrate 4 is constant. In the next step, components are mounted as shown in FIG.

That is, this is carried out by placing the leads 5a of the leaded surface mount component 5 on the area on the board 4 where the cream solder 2a is printed. Also, leadless surface mount components are similarly mounted by placing the electrode portions on the cream solder, and this is repeated for the number of components to be mounted to complete mounting of all components.

Lead 5 of the leaded surface mount component 5 mounted at this time
a has an inclination of a certain angle θ (θ is 01 to 10'). Next, reflow soldering is performed by heating the board 4 on which the components are mounted in a reflow oven or the like, using cream solder 2a.
This is done by melting the surface mount components and bonding them onto the substrate 4.

(Problem to be Solved by the Invention) However, as shown in FIG. 7, a leaded surface mount component has an inclined lead 5a on cream solder 2a printed to a uniform thickness on a board 4. 5, the contact surface between the lead 5a and the cream solder 2a becomes narrower.

Since the leaded surface mount component 5 is temporarily fixed by the adhesive force of the cream solder 2a, if the contact surface is narrow, the temporary fixing force is small and becomes unstable against vibrations and the like. Therefore, the position of the leaded surface mount component 5 may be displaced due to vibrations that occur when other components are mounted or during transportation to the flow furnace. When the leaded surface mount component 5 is misaligned, there is a problem that solder does not stick during reflow soldering or short circuit occurs with adjacent electrodes.

An object of the present invention is to reduce the temporary lN of cream solder so as to eliminate the misalignment of surface mount components mounted on the cream solder. ! To provide a soldering method for soldering boards that greatly reduces the first bonding force.

[Structure of the Invention] (Means for Solving the Problems) The soldering method of the present invention is to apply cream solder to a predetermined thickness by screen printing on a soldering location on a board, and to apply surface mount components onto the cream solder. Attach the soldered part of
For reflow soldering of surface mount components by heating cream solder, the shape of the cream solder applied to the lead portion of the surface mount component to be soldered is graded so that it is thinner at the tip of the lead and thicker at the base. It is characterized by being formed into a shape.

(Function) According to the soldering method of the present invention, the cream solder is printed in steps in the thickness direction at the soldering location on the board, so that the leads of the surface mount component with leads whose leads are inclined When placed on top of printed cream solder, the contact area between the cream solder and the lead increases, increasing the adhesion force, making it stable against vibrations, etc., and preventing misalignment.

(Example) An example of the present invention will be described below with reference to FIGS. 1 to 4.

FIG. 1 is a partially enlarged view showing the soldering method of the present invention. As shown in FIG. 1, 4 is a board, and cream solder 2a is printed in steps in the thickness direction at soldering locations 4a on the board 4. Reference numeral 5 denotes a leaded surface mount component, and a large number of leads 5a having inclined tips are formed from this leaded surface mount component 5, and these leads 5a are placed on the printed cream solder 2a.

A method for shaping this cream solder 2a will now be described. First, as shown in FIG. 2, 1 is a flat mask, and this mask 1 has a slit 1a cut out at the soldering location of the lead 5a that requires soldering of the leaded surface mount component 5. has been done. This slit 1a has a groove 1b formed outward from the middle thereof, and the groove 1b
The thickness of the plate is thinner. This allows slit 1
The cross-sectional shape of a in the longitudinal direction is a blue a (L) shape.

Next, as shown in FIG. 3, this mask 1 is placed on the substrate 4, cream solder 2 is placed on the mask 1, and the squeegee 3 is moved while pressing against the mask 1 including the inner part of the groove 1b. By doing so, cream solder 2a is formed in the slit 1a in an L-shaped cross section. After that, by removing the mask 1 from the substrate 4,
As shown in FIG. 4, a slit 1 provided in a mask 1
Cream solder 2a is printed on the substrate 4 in the L-shape a, that is, in the step shape.

Next, the inclined leads 5a of the leaded surface mount component 5
When placed on the cream solder 2a, the leads 5a and the cream solder 2a come into contact at two places, as shown in FIG. When the horizontal projection dimension L of the soldering point 5b of the lead 5a of the leaded surface mount component 5 is 1.2 mm, and the lead inclination θ is 5@, the difference in height between the lead tip 5c and the bent portion 5d is Ltanθ. It is 0.105+u. Since the level difference of the cream solder 2a is printed at approximately 0.1+a+s, the leading end portion 5c and the bent portion 15d of the lead will surely come into contact with the cream solder 2a.

Next, the substrate 4 on which the surface mount component 5 is mounted is moved to a reflow oven (not shown). Although the board 4 is subjected to vibrations due to the movement after the surface mount component is mounted, no displacement occurs because the leaded surface mount component 5 is reliably temporarily fixed to the cream solder 2a. Then, the board 4 on which the surface mount component 5 is mounted is heated in a reflow oven, and the cream solder 2a is heated.
is melted and the surface mount component 5 is soldered onto the board 4.

As described above, according to this embodiment, the cream solder 2
By making the printed shape of a step-like, the leaded surface mount component 5 whose leads 5b are slanted can be soldered with cream solder 2.
Since it is possible to reliably temporarily fix the soldering device on the top surface of the soldering device A, good flow soldering can be performed without positional deviation even in the case of vibrations that occur when other components are mounted or moved to a flow furnace.

[Effects of the Invention] In the present invention, by making the printed shape of the cream solder step-like in the thickness direction, it is possible to eliminate the occurrence of misalignment of the leaded surface mount component mounted on the cream solder, and it is possible to eliminate the occurrence of positional shift during reflow soldering. It is possible to provide a good soldering method that does not cause problems such as non-solder adhesion or short-circuiting with adjacent electrodes.

[Brief explanation of drawings]

FIG. 1 is a partially enlarged view of a soldering method showing an embodiment of the present invention, FIG. 2 is a plan view of a mask applied to FIG. 1, and FIG.
4 and 4 are explanatory views of the cream solder forming method applied to FIG. 1, respectively, and FIGS. 5 to 7 are explanatory views showing the conventional method. 1...Mask, 1a...Slit, 2
... Cream solder, 2 a ... Stepped cream solder, 3 ... Squeegee, 4 ... Board, 5 ... Surface mount component with lead 5 a ... Lead, 5 C ... - Lid tip.

Claims (1)

[Claims] Apply cream solder to a predetermined thickness on the soldering points on the board by screen printing, attach the soldered parts of the surface mount components onto this cream solder, heat the cream solder, and reflow solder the surface mount components. The soldering method is characterized in that the shape of the cream solder applied to the lead portion of the surface mount component to be soldered is formed in a stepped manner so that it is thinner at the tip of the lead and thicker at the base. Soldering method.