JPH0311791A - Mounting of electronic component - Google Patents

Abstract

PURPOSE:To make a solder layer thin by enabling solder to spread over the whole face of a land and to make an angular moment, which acts on a component, small by a method wherein cream solder is applied to only the regions of a pair of electrode lands where both the end electrodes of a chip-like electronic component are brought into contact when the chip-like electronic component is fixed onto a printed board through a reflow oven. CONSTITUTION:An electrode pattern 1 and a printed board 3 of alumina or the like on which a pair of electrode lands have been formed are prepared, and cream solders 7 are printed only on regions 6 of lands 2 through a mesh or metal printing screen, where the end electrodes 5 of a chip-like electronic component 4 are brought into contact with the regions 6. Then, the component 4 is mounted on the board 3 so as to enable the underside of the lengthwise end electrodes 5 of the component 4 to come into contact with the regions 6 of the lands 2 where the solder 7 have been applied, which is made to pass through a reflow oven to be thermally treated. By this setup, the component 4 never rises up even if the solder 7 are different from each other in fusion rate and wettability.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention mainly relates to a method for mounting chip-shaped electronic components such as chip capacitors and chip resistors using a reflow oven.

(Prior art) Conventional methods of this type include those shown in Figs. 6(a) and (b) and 8.
As shown in Figures (a) and (b), an electronic component C is provided on a printed circuit board a and has electrode portions at both ends.
Apply cream solder e, e to the respective surfaces of a pair of electrode lands d, d, each having a larger area than the projected area of the electrode portions s, b, of the electronic component C. It is known that the electronic component C is mounted on the printed circuit board a by being mounted so as to be in contact with the respective cream solders e and e and subjected to heat treatment.

(Problem to be solved by the invention) However, the conventional example shown in FIGS. 6(a) and (b) above has the following problems:
The electrode land d is large, and the cream solder e is applied to the entire surface of the electrode land d. According to this, both the cream solder e and e adhering to the picture electrode portions of the electronic component C during reflow are removed. If there is a difference in the melting speed of the electronic component C, or if there is a difference in the solder wettability of the end surfaces f and f of the electrode parts A and B of the electronic component C, the electronic component C will quickly melt the cream solder and the wetter molten solder. Due to the surface tension of the electronic component C, there is a disadvantage that the electronic component C stands up on the end surface side that gets wet earlier, as shown in FIG. In addition, in order to eliminate this inconvenience, there is an example in which a thin layer of cream solder is applied to reduce the amount of cream solder e, e that adheres to the end face of the electrode parts A and B, thereby reducing the rotational moment applied to the electronic component C. In this case, since the cream solders e and e do not have the holding power for the electronic component C, there is a problem that even a slight vibration or the like may cause the electronic component C to move after the electronic component C is mounted and before reflow. Also,
In order to reduce the rotational moment, the above figure 8(a)
In the conventional example (b), the window of the electrode land d or solder resist is small, and cream solder is applied to the entire surface of the electrode land c1 or the window of the solder resist. According to this, cream solder e is applied thinly. If the cream solder is applied too thickly, the amount of cream solder that adheres to the electronic components after the solder flows will increase, and if there is a sudden temperature change, the same problem as described above will occur. This causes problems in terms of reliability, such as the occurrence of cracks.

(Means for Solving the Problems) The present invention aims to provide a method for mounting electronic components that eliminates the disadvantages of the above-mentioned conventional example. Cream solder is applied to the surface of each of a pair of electrode lands having a larger area than the projected area of the electrode portion of an electronic component having an electrode portion on the part, and each electrode portion of the electronic component is bonded with the cream solder. In the method of mounting the electronic component on the printed circuit board by mounting the electronic component so as to make contact with the printed circuit board and performing heat treatment, the area where the electrode portions at both ends of the electronic component come into contact when the electronic component is mounted is The method according to claim 2, characterized in that the cream solder is applied only to the surfaces of the pair of electrode lands, the projected area of the electrode portion of an electronic component provided on a printed circuit board and having electrode portions at both ends. Apply cream solder to the surface of each of a pair of electrode lands having a larger area than In the method of mounting a component on the printed circuit board, the surfaces of the pair of electrode lands at the portions where the electrode portions of the electronic component come into contact have substantially the same shape and the same area as the projected area of the electrode portions at both ends of the electronic component. The method according to claim 3 is characterized in that the cream solder is applied to a pair of electronic parts provided on a printed circuit board and having an area larger than the projected area of the electrode parts of an electronic component having electrode parts at both ends. Cream solder is applied to the surface of each of the electrode lands, each electrode part of the electronic component is mounted so as to be in contact with the cream solder, and the electronic component is mounted on the printed circuit board by heat treatment. In the method, the cream solder is applied to the surfaces of the pair of electrode lands at a size and spacing such that when the electronic component is mounted, it does not protrude beyond the longitudinal end surface of the electronic component. It is characterized by

(Function) According to the method of claims 1 to 3, the cream solder is applied only to the area where the electrode portions at both ends of the electronic component of the pair of electrode lands contact, so that the cream solder is not applied during reflow. As the solder spreads over the entire surface of the electrode land, the thickness of the solder layer becomes thinner, and the rotational moment acting on the electronic component becomes smaller, preventing one end of the electronic component from floating or causing the electronic component to stand up. Moreover, when electronic components are mounted, the amount of cream solder before reflow can be applied to a thickness sufficient to hold them.

(Example) Next, embodiments of the present invention will be described with reference to the drawings.

1 to 3 show a first embodiment of the present invention,
This will be explained below.

First, a printed circuit board 3 made of alumina or glass epoxy, on which an electrode pattern 1 and a pair of electrode lands 2.2 are formed.
Prepare.

Next, only the regions 6, 6 where the electrode portions 5.5 at both ends of the chip-shaped electronic component (chip capacitor, chip resistor, etc.) 4 of the predetermined electrode land 2°2 contact (both ends of the electronic component 4) A printing screen made of mesh or metal and having an opening at a location corresponding to the area in which the electrode portions 5.5 of the electronic component 4 come into contact, having approximately the same shape and the same area as the projected area of the electrode portions 5, 5 of the electronic component 4. is prepared, and using the screen, cream solder 7 is printed on the areas 6, 6 of the electrode lands 2, 2 through the openings, as shown in FIG. 1, by screen printing.

Next, the chip-shaped electronic component 4 is placed so that the lower surfaces of the electrode portions 5, 5 at both longitudinal ends thereof are in contact with the areas 6.6 on which the cream solder 7, 7 of the pair of electrode lands 2, 2 is applied. It is mounted on the printed circuit board 3 as shown in Figure 2.

Finally, the printed circuit board 3 on which the electronic component 4 is mounted is passed through a reflow oven and subjected to heat treatment, and the electronic component 4 is soldered as shown in FIG.

In this case, as described in the section of the above-mentioned operation, the cream solder 7 spreads over the entire surface of the electrode land 2 during reflow and becomes thinner, so that the cream solder 7.7 on the pair of electrode lands 2,2 Even if there is a difference in melting speed or solder wettability, one end of the electronic component 4 may float due to the rotational moment due to the surface tension of the cream solder 7, 7, or the electronic component 4 may There is no such thing as standing up.

Furthermore, the amount of cream solder 7 before reflow can be applied to a thickness sufficient to hold the electronic component 4, and the electronic component 4 will not move even if there is vibration.

FIG. 4 shows a second embodiment of the present invention. In the first embodiment, the cream solder 7 was printed on the edge of the electrode land 2, but in this embodiment, the cream solder 7 was printed on the central part of the electrode land 2. printed on.

FIG. 5 shows a third embodiment of the present invention. In this case, the electronic component 4 has a size that does not protrude beyond the longitudinal end surface of the electronic component 4 when it is mounted. Cream solder 7.7 is applied to the surfaces of the pair of electrode lands 2, 2 at intervals of and, and in order to further increase the soldering strength, the cream solder 7.7 is applied in the width direction of the electronic component 4 slightly larger than its projected area. 7 was applied.

(Effects of the Invention) As described above, according to the present invention, even when heat treatment is performed, there is no problem such as one end of the electronic component lifting up or the electronic component standing up, and the electrodes on the printed circuit board can be fixed. An appropriate amount of cream solder is applied to the land, and electronic components can be reliably mounted.

[Brief explanation of the drawing]

1 to 3 are diagrams explaining the procedure of the first embodiment of the method of the present invention, in which FIG. 1 is a plan view of the main parts before electronic components are mounted on a printed circuit board, and FIG. FIG. 2 shows a cross-sectional side view of the main part before electronic components are mounted on a printed circuit board or flow, and FIG. 3 shows a cross-section side view of the main part after the beam flow. FIG. 4 is a cross-sectional side view of the main part of the second embodiment of the method of the present invention, and FIG. 5 is a plan view of the main part of the third embodiment of the method of the present invention. Figures 6(a) and 6(b) are a plan view and a side view of the first conventional example, Figure 7 is a diagram explaining the disadvantages thereof, and Figure 8 (
a) and srm rb) are a plan view and a cross-section side view of the second conventional example.

Claims (3)

[Claims] 1. Cream solder is applied to the surface of each of a pair of electrode lands having a larger area than the projected area of the electrode parts of an electronic component provided on a printed circuit board and having electrode parts at both ends, and each of the electronic parts is In the method of mounting the electronic component on the printed circuit board by mounting the electrode portions of the electronic component so as to contact each of the cream solder and performing heat treatment, both ends of the electronic component are mounted on the printed circuit board. A method for mounting an electronic component, characterized in that the cream solder is applied only to the surfaces of the pair of electrode lands in areas where the electrode portions of the parts come into contact. 2. Cream solder is applied to the surface of each of a pair of electrode lands having a larger area than the projected area of the electrode parts of an electronic component provided on a printed circuit board and having electrode parts at both ends, and each of the electronic parts is In the method of mounting the electronic component on the printed circuit board by mounting the electrode components so as to be in contact with the cream solder and heat-treating the electronic component, the projected area of the electrode portions at both ends of the electronic component is approximately A method for mounting an electronic component, characterized in that the cream solder is applied to the surfaces of the pair of electrode lands of the same shape and the same area and in contact with the electrode portions of the electronic component. 3. Cream solder is applied to the surface of each of a pair of electrode lands having a larger area than the projected area of the electrode parts of an electronic component provided on a printed circuit board and having electrode parts at both ends, and each of the electronic parts is In the method of mounting the electronic component on the printed circuit board by mounting the electrode portions of the electronic components so as to contact each of the cream solders and subjecting the electronic components to heat treatment, when the electronic component is mounted, the longitudinal direction of the electronic component is A method for mounting an electronic component, characterized in that the cream solder is applied to the surfaces of the pair of electrode lands at a size and interval such that the cream solder does not protrude beyond the end face in the direction.