JPH0444389A - Connection method of packaging type ic - Google Patents

Abstract

PURPOSE:To make it possible to maintain high reliability for a packaged type IC and connect collectively by installing a specific cut in a lead of said packaged type IC, and bonding the lead with an electrode under the application of pressure. CONSTITUTION:A cut 5 is installed to at least one of the connection sections with an electrode 2 of a lead 4 so that the cut 5 may be directed at the cross sectional direction of the lead 4. Under the application of pressure, the connection sections, which include this cut section 5 are bonded with the electrode 2 by means of an adhesive agent 6. The depth of the cut 5 is preferably 1/2 the cross section of the lead 4. Most preferably, the depth of the cut ranges from 20 to 50 mum. When the cut is too shallow, large pressure application is called for to correct the unlevelness of the lead or sometimes, proper correction effect is unavailable. On the other hand, when the cut is too deep, the strength of the cut section may drop extremely or break easily, especially under the application of pressure. As for the location of the cut 5 to be installed, any position is acceptable only if the cut is located from the corner of the lead 4, which comes into contact with the electrode 2 ad the end of the lead.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for connecting packaged ICs mounted on circuit boards and used in fields such as the mechanical industry and the electrical/electronic industry.

[Conventional technology]

Conventionally, the method of connecting a packaged IC (hereinafter abbreviated as IC) to a circuit board is to print solder paste on the electrode part of the circuit board, align the leads extending from the IC to this part, and then A common connection method is to pass the lead through a heating furnace and solder it to the electrode.

However, such a connection method has the following problems.

■ Lack of accuracy in the height direction of IC leads, handling, etc. often result in differences in height between the leads. For this reason, during soldering, stress acting in the height direction of the IC lead later causes incomplete connection between the electrode of the circuit board and the IC lead, or disconnection. This tendency is the same for connection materials other than solder, and is even more pronounced when a conductive adhesive is used, for example, making it impossible to obtain reliability of the connection portion.

■ When the distance between adjacent leads becomes narrower, connecting materials such as solder cannot maintain insulation between adjacent circuits, making it impossible to support high-density circuits.

[Problem to be solved by the invention]

The present invention solves the above-mentioned problems and connects packaged ICs to a circuit board at once with high reliability without using the conventional technique of soldering. It is intended to provide a method.

[Means to solve the problem]

The inventors of the present invention have conducted extensive research in order to solve the above problem, and have found that by making specific notches in the leads of packaged ICs and bonding the leads with adhesive while applying pressure to the electrodes, the purpose of the present invention can be achieved. The present invention was completed based on this finding.

That is, the present invention provides a notch in the cross-sectional direction of the lead at least at one location in the connecting portion of the lead extending from a packaged IC with an electrode on the circuit board, and the connecting portion of the lead including this notch is provided on the circuit board. A packaged IC characterized by being adhered to the electrode with an adhesive while applying pressure.
This provides a connection method.

Hereinafter, the present invention will be explained based on the drawings.

FIG. 1 is a partial sectional view showing an example of a connection state in which a packaged IC (hereinafter abbreviated as IC) is connected to an electrode according to the present invention, and FIG. 3 is a partial perspective view thereof. however,
In FIG. 3, details such as electrodes on the circuit board are omitted.

1 is a circuit board, which has an electrode 2 on its surface. As the circuit board 1, any material such as one made of glass epoxy can be used.

The electrode 2 is formed so as to face and correspond to each lead 4 extending from the IC 3 to be connected to the circuit board l. As the electrode 2, Cu or Cu/P b
-S n or the like can be used.

A lead 4 extending from the IC 3 and an electrode 2 are aligned and connected.

Here, any IC3 can be used, but the present invention is particularly suitable for - QFP (Quad
Flat Package), S.

P (Small 0ut-1ine Pa
The present invention is preferably applied to so-called flat package type ICs, such as those called ckage. It is preferable that the leads 4 extend from the sides of the IC. The leads may extend in one or more directions with respect to the IC. As illustrated in FIG. 3, the leads may extend in four directions from the four sides of the IC.

Further, the cross-sectional shape, length, etc. of the lead 4 are not particularly limited as long as it is suitable for connection onto a predetermined electrode 2.

In the connection method of the present invention, a notch 5 is provided in the cross-sectional direction of the lead 4 at at least one location of the connection portion of the lead 4 with the electrode 2, and the connection portion of the lead 4 including this notch 5 is connected to the electrode 2.
It is attached with adhesive 6 while applying pressure.

The depth of the cut 5 formed in the lead 4 is preferably about one half of the cross section of the lead 4. Particularly preferably 20-5
The thickness should be 0 μm. If the cut is too shallow, a large pressing force may be required to correct the step difference in the lead, or a sufficient correction effect may not be obtained. In addition, if the cut is too large, the strength of the cut portion may be extremely reduced, and it may easily break when pressurized. The cut 5 can be provided at any position between the connection part of the lead 4 with the electrode 2, that is, the corner where the lead 4 contacts the electrode 2 and the end of the lead. It is preferable to determine the position depending on the type of lead 4, molding conditions, etc.

FIGS. 4(a) to 4(e) are partial sectional views showing several examples of the manner in which the notches 5 are provided in the leads 4. FIGS.

FIG. 4(a) shows an example in which a notch 5 is provided on the side where the lead 4 contacts the electrode at the corner where the lead 4 contacts the electrode. FIG. 4 CO> is an example in which the notch 5 is provided on the opposite side of FIG. 4(a), that is, on the side not in contact with the electrode. Figure 4 (C
) is an example in which, in addition to the notch 5 shown in FIG. 4(a), a notch 5 is provided between the corner on the same side as the notch and the lead end. FIG. 4(d) is an example in which, in addition to the notch 5 shown in FIG. 4(b), a notch 5 is provided between the corner on the same side as the notch and the lead end. Figure 4 (
e) is an example in which, in addition to the notch 5 shown in FIG. 4(a), a notch 5 is provided between the corner on the opposite side of the notch and the lead end.

The incisions may be made at one or more places, preferably at one or two places, as in the above example.

The incision can be formed at any time before connection with the electrode. For example, it is preferable to form the cuts before bending and shaping the lead, as this allows uniform cuts to be formed.

FIG. 5 is a partial cross-sectional view showing an example of a method of forming a cut.

First, the lead 4 is positioned and fixed on the lead holder 8.

Next, a cut forming jig 9 having a wedge-shaped rotating blade is used.
is pressed against the notch forming portion of the lead 4 extending from the IC 3, and the notch 5 is formed by advancing the notch forming jig 9 in the rotational direction. The depth of the cut 5 is preferably adjusted by adjusting the stroke of the cut forming jig 9.

The means for forming the incisions is not limited to the method shown in FIG. 5, and any method can be used.

A knife whose cutting depth can be controlled may also be used.

The connection portion of the lead including the above-mentioned notch is adhered to the electrode with an adhesive while being pressurized.

There are two ways to bond the leads and electrodes with adhesive: a conductive adhesive with the adhesive interposed between the leads and the electrodes, and an insulating adhesive. Examples include a method of adhering the lead and the electrode so that they are in direct contact with each other.

When the distance between adjacent leads is narrow, conductive adhesives such as ultraviolet curable or thermosetting adhesives with dispersed metal conductive particles such as carbon, Ag, or Ni, or polymer cores are particularly recommended as conductive adhesives. Dispersed conductive plastic particles having a thin metal layer on the surface are preferably used. These adhesives are anisotropically conductive adhesives that exhibit insulating properties in the plane direction after bonding.

In FIG. 1, an anisotropic conductive adhesive having conductive plastic particles 7 is used as the adhesive 6. When using an anisotropic conductive adhesive in this manner, it is preferable that the leads 4 and the electrodes 2 be bonded via the adhesive 6. Electrical conduction between the lead 4 and the electrode 2 is achieved by conductive plastic particles 7 in the adhesive 6. In this case, the adhesive 6 may be placed on the electrode 2 in advance and the lead 4 may be pressed onto it, and the lead 4 and the adhesive 6 may be bonded together so that the adhesive 6 is interposed between the lead 4 and the electrode 2. It may also be pressed onto the electrode 2.

Moreover, FIG. 2 is a partial cross-sectional view of the case where the lead and the electrode are brought into direct contact and connected so as to obtain a conductive state.

A notch 5 is formed in the card 4 extending from the IC 3. The connecting portion of the lead 4 including the notch 5 is arranged so as to directly contact a predetermined electrode 2 on the circuit board 1 for electrical conduction, and the connecting portion of the lead 4 is bonded with the adhesive 6 around the contact portion. and electrode 2 are bonded to each other. In this case, an insulating adhesive can also be used as the adhesive 6.

The adhesive may be in any desired form, such as a liquid or a film. A film-like adhesive is preferable because it is relatively simple to make it have a uniform thickness.

When bonding the lead 4 to the electrode 2, pressure is applied to the connection portion of the lead 4. The pressurization is preferably carried out at a pressure of lO to 30 kgf/cIIN for 5 to 20 seconds.

FIG. 6 is a partial sectional view showing an example of the pressurizing means.

This figure shows how a connecting portion extending from the side surface of the IC 3 and including the notch 5 of the lead 4 is bonded onto the electrode 2 on the circuit board 1 via the adhesive 6. The connecting portion of the lead 4 is pressurized by a pressure head 10. Pressure hend 10
It is preferable to use a device having a heating heater 11 inside, since it is possible to pressurize and heat at the same time. When heating, the temperature is preferably 150 to 200°C.

Depending on the type of adhesive 6 used, the adhesive 6 is generally cured by using both pressure and heating, or by applying only pressure with the pressure head 10 and irradiating the adhesive 6 with ultraviolet rays. be. Further, when pressurization and heating are used together, heating methods include a method in which a pulse current is passed through the coil of the heater 11 to heat the pressurized end 10, a method in which constant heating is performed, and the like. Further, instead of using a heater, a heating method using infrared rays can be used.

[Effect]

In the packaged IC connection method of the present invention, by forming a notch in the connection portion of the IC lead, stress concentration occurs in the notch portion due to pressure applied during connection. For this reason, the lead is easily bent at this location, making good contact with the electrode to be connected, and increasing the connection area. Even if there is a difference in level between the leads, the pressure head applies uniform pressure to the electrode surface on the circuit board and is held in this state by adhesive, so that after the pressure is released, the leads can be pressed evenly to the electrode surface on the circuit board. It becomes difficult to lift off the surface. In addition, since there is little distortion in the leads, connection reliability is excellent, making it possible to perform high-precision batch connections in a short time.

Furthermore, when an anisotropically conductive or insulating adhesive is used as the adhesive, connection can be made even if the lead spacing is narrow, and it can be used even in high-density circuits.

〔Example〕

Hereinafter, the present invention will be explained in detail based on Examples, but the present invention is not limited thereto.

Example 1 A 4270 mm lead (thickness: 80 .mu.m) extending from the side surface of a packaged IC was provided with a 40 .mu.m incision at the corner of the connection portion connected to the electrode, on the side in contact with the electrode.

As shown in FIG. 6, the connection part of the lead provided with this cut is connected to the Cu/Pb
An anisotropic 1t film made of conductive plastic particles 7 dispersed in an adhesive 6 on an electrode 2 made of -Sn.
Anisolm AC7072 (Thermosetting anisotropic conductive film
(manufactured by Hitachi Chemical Co., Ltd.). Next, heater 1 with the overlapping portion placed above
1 was pressed by a pressure hand 10 having a built-in pressure head 10. At this time, pressure was applied uniformly to the electrode 2 so that the notch 5 portion of the lead 4 was easily deformed. Pressure head l at the same time
Heating was performed using an O heater 11 to melt the anisotropic conductive film 6. As a result, the conductive plastic particles 7 were deformed and electrical conduction between the leads 4 and the electrodes 2 was established, and in this state the adhesive was cured to complete the connection. Here, heating is 190°C and pressurization is 20kgf/cd.
The heating time was 10 seconds, and then the mixture was cooled for 5 seconds while being pressurized.

This connection resulted in a connection with high reliability and less distortion in the leads.

〔Effect of the invention〕

According to the method for connecting a packaged IC of the present invention, it is possible to absorb the difference in level between the leads due to lack of accuracy in the height direction of the leads, and to make a highly reliable connection to the circuit board electrode possible. In particular, it is possible to connect ICs having a high density of leads to a circuit board with high reliability.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view showing an example of a connection state in which a packaged IC is connected to an electrode according to the present invention. FIG. 2 is a partial sectional view showing an example of a connection state in which a packaged IC is connected to an electrode according to another embodiment of the present invention. Figure 3 shows
FIG. 3 is a partial perspective view showing a state in which the IC3 is connected on the circuit board l. FIGS. 4(a) to 4(e) are partial cross-sectional views showing several examples of the types of cuts provided in the leads. FIG. 5 is a partial cross-sectional view showing an example of a method of forming a cut. FIG. 6 is a partial sectional view showing an example of the pressurizing means. Explanation of symbols 1 Circuit board 2 Pole Package type I Lead incision Adhesive Conductive plastic particles Lead holder is pedestal Incision forming jig Pressure head heater Fig. 3 (b) (C) (dl (e) Fig. 4

Claims (1)

[Claims] 1. Provide a notch in the cross-sectional direction of the lead at least at one location on the connection portion of the lead extending from the packaged IC with the electrode on the circuit board, and place the connection portion of the lead including this notch on the electrode on the circuit board. A method for connecting packaged ICs, which is characterized by bonding with an adhesive while applying pressure.