JPH05267816A - Mounting of surface mount device - Google Patents

Abstract

PURPOSE:To enable mounting with high accuracy at the predetermined positions when the solder is melted by applied heat in a method of soldering a surface mount device on a printed circuit board with high accuracy. CONSTITUTION:In a mounting method for soldering connecting terminals in both sides of a surface mount device to a printed circuit board having corresponding wiring pads, through holes 3 are provided respectively for at least two connecting terminals 2 in both sides, a through hole 7 matching with the through hole 3 is formed corresponding to the wiring pad 6 and the soldering is carried out so that the through hole 3 matches with a through hole 7. Moreover, it is also possible to provide a recessed area 13 at the external end face respectively for at least two connecting terminals 12 at both ends.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to mounting a semiconductor device on a printed wiring board, and more particularly to a method for soldering surface mount devices to the printed wiring board with high accuracy.

[0002]

2. Description of the Related Art Conventionally, semiconductor devices (IC, LSI, etc.)
The method of mounting on the printed wiring board is to insert the lead wire into the through hole (conduction hole) provided on the printed wiring board,
The mainstream method was fixing by soldering. On the other hand, the surface mounting method of soldering the terminals of the semiconductor device to the surface conductor pattern (wiring pad) of the printed wiring board without using the lead wire insertion hole is increasing, and this is becoming the mainstream.

With the recent demand for miniaturization of satellite broadcasting receivers, high performance semiconductor (surface mount) devices in the 10 to 20 GHz microwave band have been required. For this,
Devices such as HEMTs have been provided. However, due to subtle impedance variations caused by mounting accuracy on the printed wiring board, the specified performance of the device cannot be obtained (noise and gain do not reach the specified levels). Need to be mounted precisely.

In the conventional surface mount device for microwaves, each of the plurality of terminals has a flat plate shape,
There are no through holes or end recesses in the terminals. On the other hand, the wiring pads for terminal connection on the surface of the printed wiring board are usually rectangular conductor metal patterns. Depending on the case, the wiring pad may have a through hole (contact hole), but this through hole is provided in the circuit design of the multilayer wiring.

In order to mount this device on a printed wiring board, solder paste is applied onto the wiring pads of the printed wiring board by screen printing or the like, the terminals of the device are placed on the solder paste, and then the reflow furnace ( For example, it is heated in an infrared heating furnace) to melt the solder so that the molten solder wets and covers the terminals, and is then soldered by cooling and solidification.

[0006]

However, when the solder is melted, the surface mount device moves on the wiring pad, and the fixing (mounting) position fluctuates. Such fluttering causes a slight impedance variation in the microwave band, resulting in deterioration of characteristics such as noise and gain.

An object of the present invention is to provide a mounting method that enables a surface mount device to be mounted at a predetermined position on a printed wiring board with high accuracy when solder is melted by heating.

[0008]

In the mounting method of soldering the both-sided connection terminals of the surface-mounted device to a printed wiring board having wiring pads corresponding to these, at least two of the both-sided connection terminals are provided. Surface mounting characterized in that a through hole is provided in each of the wiring holes, a through hole corresponding to the through hole is formed at the wiring pad, and soldering is performed so that the through hole matches the through hole. This is achieved by the mounting method of the device.

Further, instead of the through hole, a recess may be provided in the outer end surface of each of at least two of the both-side connecting terminals.

[0010]

[Operation] Solder that wets and connects to the wiring pad of the printed wiring board and the terminal of the surface-mounting device also flows into the through hole during melting, and the surface tension and flow of the molten solder cause the terminal of the terminal in the through hole of the printed wiring board. The device is positioned in a self-aligned manner so that the through holes (or recesses) are aligned. If they are off,
The surface mount device moves into place. That is, the position of the surface mount device is automatically corrected in the process of melting and solidifying the solder, and the device can be mounted with high accuracy at a position determined by the position of the through hole. If there is one through-hole and one corresponding terminal through-hole, it will move so as to oscillate around that, so that at least a pair of through-holes and a corresponding pair of through-holes should sandwich the element portion of the device. It is provided in.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings by way of example embodiments of the present invention. FIG. 1 is a schematic cross-sectional view showing a state in which a surface mount device is mounted on a printed wiring board by a mounting method according to the present invention, and FIG. 2 is a schematic top view thereof (however, solder is omitted).

The surface mount device 1 has four terminals 2, two of which are provided with through holes 3. On the other hand, the printed wiring board 5 has wiring pads 6 on its surface.
4 are also provided, and through holes 7 are provided in two of them. A pair of through holes 3 and a pair of through holes 7
And correspond, and the hole diameter and the hole interval (distance) are made equal. There may be some differences in the hole diameter.

To mount the surface mount device 1 on the printed wiring board 5, first, the solder paste 9 is applied onto the wiring pad 6 by screen printing. Then, the surface mount device 1 is mounted on the printed wiring board 5 so that the terminals 2 of the surface mount device 1 are placed on the solder paste 9. This is placed in an infrared heating reflow furnace (not shown) and heated to a temperature at which the solder melts. When the solder is melted, it wets the terminal 2 and covers it.

At this time, as shown in FIG. 3, if the through hole 3 of the surface mount device 2 and the through hole 7 of the printed wiring board 5 are misaligned with each other, the surface tension of the molten solder 9 and the contact to the through hole 7 are increased. Flow (arrow A) causes terminal 2
A force in the direction of the arrow B acts on the device 1, and the device 1 moves so that the through hole 3 of the terminal 2 and the through hole 7 are aligned with each other. Then, it becomes the position of the device 1 shown in FIG. If the through hole 3 and the through hole 7 are not displaced, the state of FIG. 1 is obtained and maintained.

Next, when the solder is cooled (or cooled in the furnace) by being taken out from the furnace and solidified, soldering is performed in the state shown in FIG. Is completed. As an alternative to the above-mentioned through holes, as shown in FIG.
At least two of the one terminals 12 can be provided with recesses 13 on their respective outer end faces. These recesses 1
Reference numeral 3 corresponds to the through hole 7 of the wiring pad 6. The shape of the recess 13 may be a rectangle as shown, or may be a semicircle of the hole of the through hole 7. In such a recess,
When the solder is melted, the surface tension and the flow of the solder act as described above, and the mounting position of the device 11 can be accurately determined.

[0016]

As described above, according to the mounting method of the present invention, the surface mount device can be soldered and mounted at a predetermined position of the printed wiring board with high accuracy and without variation.
The characteristic loss of the microwave band semiconductor device can be reduced. Therefore, the performance of the microwave band receiver and the like can be improved. The method of the present invention can be applied to the mounting of a general semiconductor device on a printed wiring board, and the mounting positioning of the device can be accurately performed.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a surface mount device and a printed wiring board according to a mounting method of the present invention.

FIG. 2 is a schematic top view of the surface mount device and the printed wiring board in FIG.

FIG. 3 is a schematic cross-sectional view showing a state in which the surface mount device and the printed wiring board are displaced when solder is melted in the mounting method of the present invention.

FIG. 4 is a schematic top view of a surface mount device having printed terminals and a printed wiring board.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Surface mount device 2 ... Terminal 3 ... Through hole 5 ... Printed wiring board 6 ... Wiring pad 7 ... Through hole 9 ... Solder 11 ... Surface mount device 12 ... Terminal 13 ... Recess

Claims (2)

[Claims] 1. A mounting method for soldering both side connection terminals of a surface mount device to a printed wiring board having wiring pads corresponding thereto, wherein at least two of the both side connection terminals (2) have through holes (3). ) Is provided and a through hole (7) corresponding to the through hole is formed at the wiring pad (6), and soldering is performed so that the through hole (3) matches the through hole (7). A method for mounting a surface mount device, the method comprising: 2. A mounting method of soldering both side connection terminals of a surface mount device to a printed wiring board having wiring pads corresponding to the both side connection terminals (1).
2) a recess (13) is provided on the outer end surface of each of at least two of them, and a through hole (7) corresponding to the recess is formed at the wiring pad (6), and the recess (13) is formed. The method for mounting a surface mount device is characterized in that the soldering is performed so that the above) corresponds to the through hole (7).