JP2639288B2 - QFP mounting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
(Square planar package: quad flat pac
kage).

[0002]

2. Description of the Related Art Conventionally, there are known methods shown in FIGS. 2A to 2E for mounting on both sides of a printed circuit board and mounting a QFP.

First, as shown in FIG. 2A, a land 2 formed on a printed circuit board 1 and an opening 4 of a metal mask 3 are aligned and supplied onto the metal mask 3. The cream solder 5 is supplied to the land 2 by leveling the cream solder 5 with a squeegee 6. Next, as shown in FIG. 2B, the metal mask 3 is removed, and a thermosetting adhesive 14 filled in the syringe 13 is applied from the application nozzle 15 to the land 2 on the printed circuit board 1.
Apply in between. Next, as shown in FIG.
7 in a state where the main body 8 of the nozzle 7 is sucked by the suction head 10,
The lead 9 of the FP 7 is aligned with the land 2 of the printed circuit board 1. Next, as shown in FIG. 2D, the QFP 7 is conveyed to the printed circuit board 1 side while being suctioned by the suction head 10 and pressed, so that the leads 9 of the QFP 7 are pressed against the cream solder 5 on the land 2 and , Body 8 with adhesive 14
Press In this state, as shown in FIG. Along with this heating, first, the thermosetting adhesive 14 on the printed circuit board 1 is cured to fix the main body 8 of the QFP 7 to the printed circuit board 1,
Subsequently, the leads 9 of the QFP 7 and the lands 2 on the printed circuit board 1 are soldered together with the melting of the cream solder 5, and Q
The FP 7 can be mounted on the printed circuit board 1.

As described above, when the printed circuit board 1 on which the QFP 7 is mounted by reflow soldering is turned over and another component is heated to be mounted on the printed circuit board 1 by reflow soldering, it is positioned on the lower surface of the printed circuit board 1. Since the QFP 7 is fixed to the printed circuit board 1 by the adhesive 14, it is possible to prevent the solder joint between the land 2 and the lead 9 of the QFP 7 from falling even if the solder is re-melted.

[0005]

However, in the above-mentioned conventional mounting method, as shown in FIG.
When the printed circuit board 1 on which is mounted is heated, the adhesive 14 interposed between the printed circuit board 1 and the main body 8 of the QFP 7
Will cure earlier. Originally, without the adhesive 14, the cream solder 5 on the land 2 of the printed circuit board 1 melts, and the QFP 7 moves in the direction of the land 2 due to its own weight and the surface tension of the solder 5, so that the leads 9 of the QFP 7 are printed. Solder joining is performed in a state close to contact with the land 2 of the substrate 1 to form an ideal solder fillet. However, the adhesive 14 previously hardened as described above moves due to the weight of the QFP 7 due to its own weight. Hinder QFP7
Lead 9 is slightly floated to the land 2 of the printed circuit board 1 and causes solder joint failure.

The present invention solves the above-mentioned conventional problem, in which a printed circuit board on which a QFP is mounted is inverted, and the QFP is held in a previously mounted state even when heated to mount another component. Accordingly, it is an object of the present invention to provide a QFP mounting method capable of suppressing a lead floating defect of a QFP and maintaining an ideal bonding state.

[0007]

According to the present invention, in order to achieve the above object, a thermosetting adhesive is provided across the body of the QFP and the printed circuit board after soldering a lead of the QFP to the printed circuit board. An agent is applied.

[0008]

Therefore, according to the present invention, when a printed circuit board on which a QFP is mounted by soldering is turned over and heated to mount components, the thermosetting adhesive is cured before the solder on which the QFP is mounted. Therefore, the QFP can be held in a state where the QFP is first mounted on the printed circuit board by soldering.

[0009]

An embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1A to 1F are process explanatory diagrams showing a method of mounting a QFP in one embodiment of the present invention.

First, as shown in FIG. 1A, the lands 2 formed on the printed circuit board 1 are aligned with the openings 4 of the metal mask 3, and the cream supplied on the metal mask 3 is adjusted. The cream solder 5 is supplied onto the lands 2 by a solder printing method in which the solder 5 is smoothed with a squeegee 6.

Next, as shown in FIG. 1B, with the metal mask 3 removed and the main body 8 of the QFP 7 suctioned by the suction head 10, the leads 9 of the QFP 7 are positioned on the lands 2 of the printed circuit board 1. Match.

Next, as shown in FIG.
The printed circuit board 1 is sucked by the suction head 10.
The lead 9 of the QFP 7 is pressed against the cream solder 5 on the land 2.

Next, as shown in FIG.
By heating with the radiant heat 12 of 1, the lead 9 of the QFP 7 and the printed circuit board 1 are melted together with the melting of the cream solder 5.
The upper land 2 is soldered, and the QFP 7 is fixed to the printed circuit board 1. At this time, unlike the mounting method of the conventional example described above, since no adhesive is interposed between the main body 8 of the QFP 7 and the printed circuit board 1, the QFP 7 is printed in an ideal state with no solder joint failure due to lead floating. Substrate 1
Fixed to

Next, as shown in FIG. 1E, the syringe 13 extends over the corner of the main body 8 of the QFP 7 soldered to the printed board 1 and the printed board 1 as described above.
The thermosetting adhesive 14 filled in the inside is applied from an application nozzle 15.

Next, as shown in FIG.
The printed circuit board 1 to which is soldered is turned over, the cream solder 5 is supplied to the lands 2 on the back surface in the same manner as described above, and the chip components 16 are mounted. Then, heater 1
By heating with the radiant heat 12 of one, the soldering of the chip component 16 is performed with the melting of the cream solder 5. At this time, the thermosetting adhesive 14 applied over the corner of the main body 8 of the QFP 7 on the back surface of the printed circuit board 1 and the printed circuit board 1 is brought to the eutectic point temperature (183 ° C.) of the cream solder 5. Cures before reaching. This makes QF
Even if the cream solder 5 connecting the lead 9 of the P7 and the land 2 of the printed circuit board 1 is re-melted, the QFP 7 does not fall because the adhesive 14 holds the QFP 7.
Is held fixed to the printed circuit board 1. Therefore, it is possible to maintain a state in which the QFP 7 is mounted on the printed circuit board 1 first, that is, an ideal solder joint state.

[0017]

As described above, according to the present invention, after a QFP is soldered to a printed circuit board, a thermosetting adhesive is applied across the body of the QFP and the printed circuit board. Therefore, even if the printed circuit board on which the QFP is mounted is turned over and heated to mount another component, the QFP can be maintained in a state where the QFP is mounted first. It is possible to maintain the ideal bonding state by preventing the bonding.

[Brief description of the drawings]

FIGS. 1A to 1F show Q in one embodiment of the present invention.
Process explanatory drawing showing FP mounting method

FIGS. 2A to 2E are process explanatory views showing a conventional QFP mounting method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printed circuit board 2 Land 3 Metal mask 5 Cream solder 7 QFP 8 Main body 9 Lead 10 Suction head 11 Heater 13 Syringe 14 Thermosetting adhesive 16 Chip component

Claims (1)

(57) [Claims] 1. A method of soldering a QFP lead to a printed circuit board, and applying a thermosetting adhesive across the body of the QFP and the printed circuit board.
FP mounting method.