JP2000321196A - Method for measuring adhesive strength of conductive pad - Google Patents

Abstract

(57) [Problem] To accurately measure the adhesion strength of minute conductive pads of a wiring board for an area array package such as a BGA by a simple method. According to the present invention, the tip of a contact tool (3) is brought into contact with a side surface of a minute (for example, 300 μm in diameter) conductive pad (2) formed on an insulating substrate (1) such as an epoxy resin impregnated glass cloth substrate. A pressing force F parallel to the surface of the insulating substrate 1 is applied via a tool. Then, the pressing force is gradually increased, and the pressing force when the conductive pad 2 is separated from the surface of the insulating substrate 1 is measured by a load sensor. If the thickness of the conductor pad 2 is small and it is difficult to apply a pressing force by bringing the contact tool 3 into contact with the conductor pad 2, a solder projection 4 having the same diameter is fixed and formed on the conductor pad 2. ,
The pressing force is applied by contacting the contact tool 3 from the side of the conductor pad 2 to the side of the solder protrusion 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the adhesive strength of a conductive pad, and more particularly, to a flip-chip connecting pad on a wiring board, a BGA (ball grid array), and the like.
The present invention relates to a method for easily measuring and evaluating the adhesive strength of a small conductor pad such as a pad for mounting a package or a CSP (chip size package).

[0002]

2. Description of the Related Art In general, the magnitude of the adhesive strength of a conductor pattern formed on a wiring board such as a printed wiring board to an insulating board is important in evaluating the connection reliability of lead terminals of electronic components to be mounted. Very important. Therefore, at the stage of the wiring board, the adhesive strength between the conductor pattern and the insulating substrate is measured as described below.

That is, conventionally, as shown in FIG. 5, an end of a conductor pattern 11 is connected to a clamper 12 of a tensile tester 12.
a, the conductor pattern 11 is pulled up by the insulating substrate 13.
The peel strength (adhesive strength) of the conductor pattern 11 was measured by determining the load when the conductor pattern 11 was peeled off from the conductor pattern 11.

[0004]

However, this method has a problem that the area of the conductor pattern 11 must be large enough to be gripped by the clamper 12a. Therefore, in an area array package such as a BGA (ball grid array) package or a CSP (chip size package), it cannot be used as a method for evaluating connection pads of a semiconductor chip. That is, in a wiring board for an area array package such as a BGA or a CSP, a large number of connection pads for flip chip bonding of a semiconductor chip are formed.
These connection pads have a structure in which they are connected to wiring patterns on the other side via via holes formed below the connection pads. These flip-chip bonding pads are extremely small (for example, 300 to 400 in diameter).
μm), so grab the end with a clamper and pull it up.
It was difficult to measure the peel strength.

In the process of forming a conductor pattern, the edge portion is liable to be deteriorated by a chemical during etching or the like. When the area of the conductor pattern is large, even if the edge portion is deteriorated, the peel strength is hardly affected.
In the case of a minute connection pad for a GA package or the like, there is a problem that high-precision measurement cannot be performed even when converted per unit area.

Further, in the measurement of the peel strength of the connection pads for the BGA package, as shown in FIG. 6A, a semiconductor chip 15 is mounted on a wiring board 14 and solder bumps 16 are formed.
After the flip chip bonding, the semiconductor chip 15 was gripped by the clamper 12a of the tensile tester 12 and pulled up, and the load when the semiconductor chip 15 was peeled off from the insulating substrate 13 together with the connection pad 17 was measured. Then, the peel strength per connection pad 17 was calculated.

However, in this method, the breaking strength of the solder bump 16 is lower than the peel strength of the connection pad 17 due to the variation in the amount of solder. In this case, as shown in FIG. 6B, the solder bump 16 is broken before the connection pad 17 is separated from the insulating substrate 13, so that the peel strength of the connection pad 17 can be measured. There was a problem that it was not possible.

The present invention has been made in order to solve such a problem, and there is provided a method for accurately measuring the adhesion strength of minute conductive pads of a wiring board for an area array package such as a BGA by a simple method. The purpose is to provide.

[0009]

According to the present invention, there is provided a method for measuring the adhesive strength of a conductive pad which is formed separately from a wiring pattern on an insulating substrate. A contact is brought into contact with the side surface of the pad, and a pressing force in a direction parallel to the surface of the insulating substrate is applied through the contact, and the pressing force when the conductor pad is separated from the surface of the insulating substrate is measured. It is characterized by the following.

In the method of the present invention, a contact for applying a pressing force is brought into contact with a side surface of the conductor pad formed on the insulating substrate, and a pressing force parallel to the surface of the insulating substrate is applied via the contact. By measuring the force required to separate the conductive pad from the insulating substrate surface, the conductive pad with a small area that is not directly connected to the wiring pattern on the substrate surface
The adhesive strength between the insulating substrate and the insulating substrate can be accurately measured by a simple method.

In particular, when the thickness of the conductor pad is small and it is difficult to make the tip of the contactor contact the side surface of the conductor pad without contacting the surface of the insulating substrate, the pad is placed on the conductor pad. It is desirable to form solder protrusions having substantially the same diameter, and apply a pressing force by contacting a touching element to the side surfaces of the solder pads and the conductor pad that is connected and integrated in this way.
By employing such a method, the contact of the touch element to the conductor pad becomes easy. Then, accurate measurement of the adhesive strength can be performed with good workability without damaging the insulating substrate or the conductive pad due to slippage of the contactor.

Further, it is also possible to fix and form a projection made of a resin which is curable at room temperature or an ultraviolet ray on the conductive pad, instead of the solder projection, and then perform the measurement. When such a resin protrusion is used, the protrusion can be formed without damaging the conductor pad (interface with the insulating substrate) by heat, and the conductor pad can be formed without heat history. Of the adhesive.

[0013]

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

In the first embodiment of the present invention, as shown in FIG. 1, minute (for example, 300 μm in diameter) formed on an insulating substrate 1 such as an epoxy resin impregnated glass cloth substrate or a BT resin impregnated glass cloth substrate. , Thickness 36 μm) The tip of a contact tool 3 of a peeling tester (not shown) is brought into contact with the side surface of the conductor pad 2, and is pushed in a direction parallel to the surface of the insulating substrate 1 via the contact tool 3. Apply pressure F. The tip of the contact tool 3 is smaller than the width (0.3 to 0.4 mm) of the conductive pad 2, for example, 0.2 to 0.3 mm in width and 50 in depth (thickness).
μm. Then, the pressing force is gradually increased in the range of 2 to 5 N, and the magnitude of the pressing force when the conductive pad 2 is separated from the surface of the insulating substrate 1 is measured by a peeling tester (load sensor).

The conductive pads 2 that can be measured include:
Conductor pads for testing as well as connection pads conducted to the other surface side of the insulating substrate through via holes, such as pads for connecting semiconductor chips (flip chip connection pads) of wiring boards such as BGA and CSP There are conductor pads that are individually formed without being directly connected to a wiring pattern on the same substrate surface, such as wire pads and wire bonding pads. In addition, even with the conductor pad connected to the wiring pattern,
In a state separated from the wiring pattern, the adhesive strength of only the conductor pad portion can be measured.

The adhesion strength measured in this manner is based on the type of the insulating substrate 1, the size of the conductive pad 2, the difference in the surface treatment of the conductive pad 2 (for example, whether or not the copper foil is blackened), the via under the conductive pad 2, and the like. It is difficult to standardize the standard because it differs depending on the presence or absence of the hole and the size of the via hole. However, the bonding strength of the conductive pad 2 having a small area which is not directly connected to the wiring pattern on the substrate surface can be accurately measured under each condition. Can be measured well.

Next, second and third embodiments of the present invention will be described.

In the second embodiment, the thickness of the conductor pad 2 is as thin as about 20 μm, and the tip of the contact tool 3 is
When it is difficult to apply a pressing force by contacting the side surface of the conductor pad 2, a protrusion 4 made of solder having the same diameter as the pad is fixed on the conductor pad 2 as shown in FIG. The contact tool 3 is brought into contact with the side surface of the solder projection 4 from the side surface of the solder protrusion 4 to apply a pressing force.

Here, the solder projections 4 can be formed on the conductor pads 2 with high dimensional accuracy by using the solder building-up means described below. That is, as shown in FIG. 3A, a solder paste 5 is applied on the conductive pads 2 by screen printing in order to make the solder pile dimensions uniform, and then, as shown in FIG. Heat to temperature to reflow solder. The size of the solder protrusion 4 after the reflow is set according to the size of the conductor pad 2 and the contact tool 3. Specifically, it has the same diameter (300 μm) as the conductive pad 2 and a height of 0.1 to 0.2 mm (for example,
150 μm).

In the second embodiment configured as described above,
The adhesive strength of the thin conductive pad 2 can be accurately measured with good workability. Further, since there is no need to repeat the contacting and pressing operations of the contact tool 3, the contact pads 2
There is no risk of damage to

In the third embodiment, as shown in FIG. 4, a projection 6 made of an epoxy resin or an acrylic resin curable at room temperature or ultraviolet light is fixed and formed on the conductive pad 2 instead of the solder. Thereafter, the contact tool 3 is brought into contact with the side surface of the conductor pad 2 and the side surface of the resin protrusion 6 formed in connection with the conductor pad 2 to apply a pressing force.

In the third embodiment in which a resin having room temperature curability is used instead of solder, the resin protrusion 6 can be formed without applying heat to the interface between the conductor pad 2 and the insulating substrate 1. In addition, the adhesive strength of the conductor pad 2 without any heat history can be easily measured.

[0023]

As is apparent from the above description, according to the method of the present invention, the bonding strength of minute conductive pads, such as flip-chip connection pads, which are not directly connected to the wiring pattern on the substrate surface is reduced. , And can be accurately measured by a simple method.

In particular, when the thickness of the conductive pad is small and it is difficult to apply a pressing force by contacting the tip of the contact with the side surface of the conductive pad, the conductive pad has the same diameter as the pad. After fixing and forming the solder projections or the resin projections such as room temperature curing, the contact pads are pressed against the side surfaces of the continuous and integrated conductor pads and the projections, thereby damaging the conductor pads. Without giving, accurate measurement can be easily performed.

[Brief description of the drawings]

FIG. 1 shows a first method of measuring the adhesive strength of a conductive pad according to the present invention.
Sectional drawing for demonstrating the Example of FIG.

FIG. 2 is a sectional view for explaining a second embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a method of forming a solder protrusion in a second embodiment.

FIG. 4 is a sectional view for explaining a third embodiment of the present invention.

FIG. 5 is a diagram showing a conventional method for measuring the adhesive strength of a conductor pattern.

FIG. 6 is a diagram showing a conventional method for measuring the peel strength of a connection pad for a BGA package.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Insulating board 2 ... Conductor pad 3 ... Contact tool 4 ... Solder protrusion 5 ... Solder paste 6 ... Room temperature curable or ultraviolet curable resin protrusion

Claims (3)

[Claims] 1. A method for measuring the adhesive strength of a conductor pad formed separately from a wiring pattern on an insulating substrate, wherein a contact is brought into contact with a side surface of the conductor pad, and A method for measuring the adhesive strength of a conductive pad, characterized by applying a pressing force in a direction parallel to the surface of the insulating substrate and measuring the pressing force when the conductive pad peels off from the surface of the insulating substrate. 2. After fixing a protrusion made of solder having the same diameter as the pad on the conductor pad, the contactor is brought into contact with the conductor pad from the side surface to the side surface of the solder protrusion. 2. A pressing force is applied.
The method for measuring the adhesive strength of the conductor pad according to the above. 3. After fixing a projection made of a room-temperature-curable or ultraviolet-curable resin having the same diameter as the pad on the conductor pad, the projection extends from the side surface of the conductor pad to the side surface of the resin projection. 2. The method for measuring the adhesive strength of a conductive pad according to claim 1, wherein the pressing force is applied by contacting a contact.