JPS61231798A - Manufacture of printed wiring body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a method for manufacturing a printed wiring body in which electronic components are soldered to both sides of a printed circuit board having conductive lands on both sides.

Conventionally, in a printed wiring body in which electronic components including chip components are soldered to both surfaces of a printed circuit board with conductive lands formed on both the front and back surfaces, through holes are used to connect the conductive lands on both surfaces of the printed circuit board. This is a method in which a metal plating layer such as copper is formed on the inner circumferential surface of a through hole that passes through conductive lands on both sides of a printed circuit board, and the conductive lands on both sides are electrically connected. Used for connections between chip components.

For example, an example of the printed circuit board and border for double-sided electronic component soldering having the above-mentioned double-sided conductive land connection through-holes is shown in the fifth example.
A conventional manufacturing example thereof will be explained below with reference to FIGS. 6 to 10.

In FIG. 5, (1) is a printed circuit board, (2) is a plurality of electronic components soldered on both sides of the printed circuit board (1), (2a) (2b) beam-dressed chip components,
(2c) is an electronic component with a lead wire (hereinafter referred to as a lead component).The printed circuit board (1) has conductive lands (4a) (4
b) and pass through the conductive lands (4a) (4b) to form a plurality of through holes (5a) (5b)-
Through holes (5a) (5b)
Copper plating layer (6a) (6b) on the inner peripheral surface of...
This figure shows that conductive lands (4a) and (4b) on both sides are selectively electrically connected by forming a conductive land (4a) and (4b) on both sides.

Soldering of the electronic component (2) to the printed circuit board (1) may be done simultaneously on both sides, but generally it is done on one side at a time in the process shown in FIGS. 6 to 10. First, as shown in FIG. 6, cream solder (7) is printed on the surface of the conductive land (4a) on the surface (m) on which the chip component is to be mounted.

Next, cream solder (7) is printed as shown in Figure 7.
The first chip component (2a) on the front side is mounted and temporarily fixed on top, and the whole is passed through a reflow oven (heating furnace) and heated to melt the cream solder (7) and form the chip component (2a).
Perform soldering in a). Next, turn the printed circuit board (1) upside down and as shown in Figure 8, apply thermosetting adhesive (8
). Then, as shown in FIG. 9, the second chip component (2b) is mounted and temporarily fixed on this adhesive (8). Next, pass the whole thing through an adhesive curing oven to apply adhesive (8
) is cured by heating, and then the printed circuit board (1) is further turned over upside down as shown in Figure 1O, and the through holes (5a
) Attach the lead wire (9>) of the lead component (2c) to (5b).
Insert (9). This printed circuit board (1) is held horizontally and its back surface is immersed in jet solder, and each of the second chip component (2b) and lead component (2c) is connected to the back surface conductive land (4b) as shown in FIG. ) to solder (10) (10
) - Connect. A known method for soldering printed wiring boards is to simultaneously perform reflow and solder dip, as disclosed in, for example, Japanese Patent Application Laid-Open No. 60-14492.

＜η・し、・ru. By the way, did you apply jet solder to the back side of the printed circuit board (1)?
ft and when soldering, a part of the jet solder creeps up inside the through-holes (5a) (5b)- by capillary action and fills the inside of the through-holes, thereby creating double-sided conductive lands (
4a) The electrical connection between (4b) becomes more reliable,
Also, make the through hole (5a) (5
The inner diameter of bL- is set. However, the copper plating layer (6a) inside the through holes (5a) (5b)
(6b) -... is oxidized by two heat treatments: heating in a glue flow furnace to melt the cream solder and heating in an adhesive curing furnace before being immersed in the jet solder, resulting in wetting with the jet solder. Through hole due to poor quality (5a)
(5b) - The amount of jet solder creeping up into the unit was sometimes insufficient. Through-hole (5a) specifically for double-sided conductive land connection where lead parts (2c) are not inserted.
The amount of solder creeping up inside the through hole (5a) is unstable, and there is often a shortage of solder (10°) buried in the through hole (5a). Such variations in the amount of solder within the through-hole (5a) result in variations in the inductance and conductance components at the double-sided conductive land connection portion of the through-hole (5a), especially in printed wiring bodies incorporating high-frequency circuits. This causes variations in characteristics, and improvements have been desired.

The present invention has been developed to meet the above-mentioned needs.When soldering electronic components to both sides of a printed circuit board in which conductive lands formed on both sides are electrically connected through metal-plated through holes, Before the first heat treatment, apply cream solder to one opening side of the through hole connecting the double-sided conductive lands,
The present invention is characterized in that the cream solder is melted during the first heat treatment to solder the inside of the through hole dedicated to connecting the double-sided conductive land.

■ If the metal plating layer in the through hole connecting the double-sided conductive lands is soldered with cream solder during the first heat treatment for soldering electronic components to a printed circuit board as in the present invention described above, the metal plating layer will be soldered with cream solder during the subsequent heat treatment. There is no fear that the layer will be oxidized, and the inside of the through hole is always filled with a certain amount of solder, so that the electrical connection of the double-sided conductive land using this through hole is stable.

The manufacturing process according to the present invention for example, the printed wiring body shown in FIG. 5 will be described below with reference to FIGS. 1 to 4.

First, in the present invention, as shown in FIG. 1, there is a through hole dedicated for connecting the first chip component mounting portion on the front side conductive land (4a) of the printed circuit board (1) and the double-sided conductive land; the upper side of the tall (5a). Cream solder on the parts (11)
print. It is desirable to print this cream solder (11) to such an extent that it closes the opening on the front side of the through hole (5a).

Next, as shown in FIG. 2, the first chip component (2a) is adhered and temporarily fixed in place on the cream solder (11). After that, put the whole thing through a reflow oven and apply cream solder (
11) is heated and melted, and the first chip component (2a) is soldered to the conductive land (4a) as shown in FIG. At this time, at the same time, the cream solder (11) on the through hole (5a) melts and flows into the through hole (5a) and adheres to the copper plating layer (6a) inside the through hole (5a). In other words, the inside of the through hole (5a) is soldered during the first heat treatment, and since the copper plating layer (6a) is not oxidized at this time, it has good wettability with molten solder, so a certain amount of solder is soldered inside the through hole (5a). Fill in with (11').

Once this reflow soldering is completed, the rest is done in the same way as before, turning the printed circuit board (1) upside down, applying the second chip component adhesive (8), mounting and gluing the second chip component (2b). Heat curing of agent (8), printed circuit board (1)
) is turned upside down and the lead components (2C) are inserted one after another.Finally, the back side of the printed circuit board (1) is immersed in jet solder to form conductive lands (4b) as shown in Figure 4.
The first chip component (2b) and lead component (2c) are soldered to. This jet soldering is also performed on the through hole (5a), and the through hole (5a)
The inside is completely filled with solder.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but can be similarly applied to cases where electronic components are soldered to both sides of a printed circuit board at the same time.

According to the present invention, the amount of solder filling the through-holes dedicated to the connection of the conductive lands on both sides of the printed circuit board is always stable.
The electrical characteristics of the printed wiring body are stabilized, and it is particularly effective for manufacturing printed wiring bodies for high frequency circuits.

[Brief explanation of drawings]

Figures 1 to 4U3! J is a partial side sectional view showing a specific example of the method of the present invention at each assembly step of a printed wiring body. FIG. 5 is a partial side sectional view of the printed wiring body, and FIGS. 6 to 1o are partial side sectional views of the printed wiring body of FIG. 5 at various assembly steps according to a conventional manufacturing method. (1) - Printed circuit board, (2) - Electronic component, (4a)
(4b) - one conductive land, (5a) - through hole for connecting double-sided conductive land, (6a) - gold a) laminate layer, (11) - cream solder.

Claims (1)

[Claims] 1) When soldering electronic components using cream solder on at least one side to a printed circuit board with conductive lands formed on both sides electrically connected through plated through holes,
A method for producing a printed wiring body, characterized in that cream solder is applied to one opening side of the through hole, and the cream solder is melted during an initial heat treatment to adhere the solder inside the through hole.