JPH10305364A - Soldering test for electronic parts and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a quantitative evaluation of the soldering highly accurate by evaluating the soldering based on the difference of powers generated between the solder paste and two pieces of testing parts under the circumstance that only a longer portion of the longer electric conductive pattern of the two testing parts is sticking out above the solder paste surface. SOLUTION: The testing parts 21a and 21b, conductive patterns of which are different, are to be held by the testing part holding methods 12a and 12b, and a micro crucible 13 is moved upward by a driving unit 15. The bottom edges of the testing parts 21a and 21b are put in positions to touch on the upper face of the micro crucible 13. The micro crucible 13 is descended by the driving unit 15 by micro gap distance and is heated by a heater 14. Viscosity of soldering paste is decreased, and wetting to the testing metal conductive parts proceeds by the soldering paste. Since the testing part 21a receives an extra power than that of the part 21b in proportion to the one the sticking out portion is affected, the surface tension can be detected as a difference of the powers the testing parts 21a and 21b respectively receive.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for quantitatively and highly accurately evaluating the solderability of an electronic component, especially a printed wiring board.

[0002]

2. Description of the Related Art Various methods have been proposed as methods for evaluating the solderability of electronic components, especially printed wiring boards, such as a solder wetting spread method, various immersion methods, and a contact angle method. ing. These are all
This is to qualitatively evaluate the solderability. On the other hand, as a method of quantitatively evaluating the solderability, a strip-shaped test piece or a test piece incorporated as a test coupon on a printed wiring board is reflow soldering tester (S
S-ST). Each of these measures one at a time.

[0003]

In order to quantitatively evaluate the solderability of a printed wiring board used for mounting, a printed circuit board having a test coupon incorporated in a discarded board is used. Although the method of cutting and performing is widely applied, even if test coupons are extracted from a printed wiring board that has been subjected to the same surface treatment, measuring multiple Variation sometimes occurred.

This is because the force applied to the test piece is affected not only by the surface tension from the melting solder paste but also by buoyancy and other noises. There was a disadvantage that was hidden. Therefore, after obtaining some data,
Data processing is performed by selecting only original data that can be determined to be probable, but there has been a problem in accuracy.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the prior art. A test piece having a different conductor pattern is attached to each of two detection means, and the test pieces are applied to each test piece. An object of the present invention is to provide a method and an apparatus for testing solderability of electronic components, which can cancel buoyancy and other noises by using a difference in force and can measure a surface tension value with high accuracy.

[0006]

In order to solve the above-mentioned problems of the prior art, a method for testing the solderability of an electronic component according to the present invention comprises providing a conductive pattern portion of the electronic component at a lower end, and at least the lower end having the same size. Using two test pieces, the shape of the conductive pattern portion of the two test pieces is formed longer from the lower end in one test piece and shorter from the lower end in the other test piece,
The two test pieces are suspended by the two external force detecting means, respectively, and the lower ends of the suspended two test pieces are placed on the solder paste placement portion in a non-melted solder paste. Into, and supported so as to form a predetermined amount of micro-gap from the solder paste mounting part surface,
Then, the solder paste was heated and melted, and the lower ends of each of the two test pieces were immersed in the molten solder paste, and only the long conductive pattern portion of the two test pieces protruded from the solder paste liquid level. State, detecting the force generated between the solder paste and the two test pieces using the two external force detecting means, and soldering based on a difference between the forces applied to the two test pieces. It is characterized by evaluating sex.

According to the method for testing the solderability of an electronic component, components other than the surface tension from the melting solder paste, such as buoyancy and other noise components, of the force applied to the test piece are offset. Therefore, it does not affect the measurement of the surface tension.

Further, when the electronic component is a printed wiring board, the solderability test method of the present invention is applied to a printed wiring board having a large area and a large variation depending on the position.

Further, the apparatus for testing solderability of an electronic component according to the present invention comprises: two test piece holding means for holding two test pieces each having a difference in the shape of the conductive pattern portion of the electronic component; Two external force detecting means respectively supporting the two test piece holding means, a solder paste mounting part on which solder paste is mounted, and a distance between each of the test piece holding means and the solder paste mounting part. And a heating mechanism for heating the solder paste, and measures buoyancy and surface tension acting on the two test pieces based on two types of output signals from the external force detection means. In addition, the solder wettability of the test piece can be measured by detecting the difference.

According to the above-described soldering test apparatus for electronic components, components other than the surface tension from the melting solder paste, such as buoyancy and other noise components, of the force applied to the test piece are offset. The surface tension value is effectively separated from these buoyancy and noise components.

Further, when the electronic component is a printed wiring board, the solderability test apparatus of the present invention can be applied to a printed wiring board having a large area and a large variation depending on the position.

[0012]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. The embodiment described below is a part of a preferred embodiment of the present invention,
Although various limitations that are preferable in terms of the technical configuration are given, the scope of the present invention is not limited to these embodiments unless otherwise specified in the following description.

FIG. 1 is a block diagram showing one embodiment of a solderability test apparatus according to the present invention. As shown in FIG. 1, a solderability test apparatus 10 according to the present invention comprises:
Two electronic balances 11a and 11b as external force detecting means
And two detection circuits 16a and 16b to which signals from the electronic balances 11a and 11b are inputted, a difference circuit 17 for taking a difference between these signals, and two test piece holding means 12a and 12b.
b and a micro crucible 13 serving as a solder paste mounting portion
And a molten solder tank 14 disposed below the micro crucible 13 and acting as a heater (heating means).

Electronic balance 11 as two external force detecting means
Each of a and 11b may have a single structure if high-speed switching is possible. Further, a driving device 15 is provided as a support means for moving the micro crucible 13 up and down. In addition,
In addition to this configuration, the driving device 15 can also move the electronic balances 11a and 11b, the test piece holding means 12a and 12b, and the like up and down with the micro crucible 13 fixed, for example.

The electronic balances 11a and 11b are fixed and held, and the output signals of the electronic balances 11a and 11b and the difference signal from the difference circuit 17 are input to an external processing unit (not shown) to operate. Force changes can be recorded.

The test piece holding means 12a and 12b are
Two chucks 12a-1 and 12b-1 for holding two test pieces 21a and 21b for solderability test, and two extendable slide shaft mechanisms 12a-2 for supporting these two chucks , 12b-2, and two electromagnetic clutches 12a-3, 12b-3 for locking the two slide shaft mechanisms. In the test piece holding means 12a, 12b, the upper ends of the slide shaft mechanisms 12a-2, 12b-2 are suspended from the electronic balances 11a, 11b.

A predetermined amount of unmelted solder paste (herein, referred to as a bulk for convenience) is placed on the micro crucible 13. The heater (heating means) 14 is controlled by a control means (not shown) to heat the micro crucible 13 to melt the solder paste and to keep the solder paste at a constant temperature.

The detection circuits 16a and 16b are connected to the electronic balance 11
a for detecting the wetting time based on the detection signals from the electronic balances 11a and 11b. For example, an action force change curve is drawn based on the detection signals from the electronic balances 11a and 11b. Is configured to read.

The difference circuit 17 includes detection circuits 16a and 16b
By subtracting the buoyancy and noise components from each other by comparing the data from, the signals hidden by these buoyancy and noise components are extracted.

FIGS. 2 to 5 show test piece holding means 12a, 1
2 shows a configuration example of test pieces 21a and 21b held by 2b. FIG. 2 is a front view showing a configuration example of one test piece, and FIG. 3 is a side view of this test piece. FIG. 4 is a front view showing a configuration example of the other test piece, and FIG. 5 is a side view of this test piece.

Each of the test pieces 21a and 21b has the same structure as an electronic component actually used, for example, a printed board, and has an insulating board 21a-
1 and 21b-1, and conductive patterns 21a-2 and 21b-2 made of copper foil or the like formed on the surface near the lower end.

In the figure, the length L1 of the insulating substrate 21a-1 is about 20 mm, and the width W is 1.0 to 3.0 mm.
And the substrate thickness t is about 0.6 to 1.8 mm. L
2, the length of L3 is arbitrary, but a difference is provided here between the shapes of the conductive patterns 21a-2 and 21b-2. For example,
The conductive pattern 21a-2 projects from the molten surface of the solder paste to several millimeters above, so that the conductive pattern is present.
On the other hand, the conductive pattern 21b-2 has a conductive pattern only up to the same height as the molten surface of the solder paste.

The solderability test apparatus 10 according to one embodiment of the present invention is configured as described above. The existing reflow soldering tester (SS-ST) measures one test piece. However, the present invention measures two test pieces at the same time and obtains a difference in force to reduce a noise portion. It is characterized by canceling and improving the accuracy of data.

Using this solderability test apparatus 10,
The test for solderability is performed as follows. The test piece holding means 12a and 12b hold test pieces 21a and 21b having different conductor patterns as shown in FIGS. 2 to 5, and a predetermined amount of unmelted (bulk) solder is placed in the micro crucible 13. The paste 13a is placed.

From this state, the micro crucible 13 is moved upward by the driving device 15. Thereby, during the movement of the micro crucible 13, the test pieces 21a,
The lower end of 21 b penetrates the solder paste 13 a in the micro crucible 13 and contacts the surface of the micro crucible 13. Thereafter, as the micro crucible 13 is raised, the micro crucible 13 pushes up the test pieces 21a and 21b.

As a result, the test piece holding means 12a, 12
b, the slide shaft mechanisms 12a-2 and 12b-2
When the lifting of the micro crucible 13 is stopped by being shortened by the rise of the test pieces 21a and 21b, the electromagnetic clutch 12a
-3, 12b-3, the slide shaft mechanism 12a
-2 and 12b-2 are locked.

In this state, the lower ends of the test pieces 21a and 21b are at positions where they come into contact with the upper surface of the micro crucible 13.
This is the zero level. Next, the driving device 15 lowers the micro crucible 13 by the micro gap, for example, several tens μm to several hundred μm. Thus, the lower ends of the test pieces 21a and 21b and the micro crucible 13
A micro gap having a predetermined dimension is formed between the upper surface and the upper surface.

At this time, the electronic balances 11a and 11b
Test holding means 12a, 12b and test pieces 21a, 2
Since the weight of 1b is applied as a load, this load is set as a tare and set to zero.

Thereafter, the heater (heating means) 14 is raised and brought into contact with the bottom surface of the micro crucible 13 so that the micro crucible 13, the solder paste 13a and the test piece 2
Heat 1a, 21b. When the heater 14 comes into contact with the bottom of the micro crucible 13, the solder paste 13 a
Dissolves in a short time.

At this time, in the process of dissolving the solder paste 13a, action forces such as buoyancy and wetting force generated between the test pieces 21a and 21b are generated. FIG. 6 is a diagram showing an acting force change curve applied to one of the test pieces, for example, 21a.

In FIG. 6, curve CV1 (acting force change curve)
Are, for example, detected by the electronic balance 11a and output as electric signals. In the same figure, a curve CV2 is a heating curve of the micropot, and the horizontal axis indicates an elapsed time.

Immediately after the start of heating, a portion of the bulk solder paste around the test piece melts first, and the density of the melted portion increases and the volume occupied decreases. At this time, the whole test piece is pulled downward transiently by the bulk movement.

As a result, the apparent downward force applied to the test piece being measured by the electronic balance transiently increases, and becomes an impulse-like waveform (maximum value A at time t0) as shown in the figure. Appear.

After the impulse-shaped maximum value A, as the heating is continued, the bulk solder paste starts to be melted in each part. As a result, the force applied to the test piece repeats irregular fluctuations. As a result, an irregular variation appears in the force CV1 applied to the test piece as shown.

In this manner, after time t0, the melting of the solder paste further proceeds, but since the heating temperature CV2 is still low, the viscosity of the molten solder base is high, and thus the contact area between the solder paste and the surface of the test piece is high. In the above, the solder paste of the solder paste to the test piece conductor metal surface has not yet occurred.

As described above, since the solder base under this temperature condition has a high viscosity, the cohesive force, that is, the surface tension of the solder base itself is large, so that the lower end of the test piece is not wet and the lower end of the test piece is not wet. It is placed on the surface tension surface of the solder base and receives an upward pushing force. This upward push force is greater than the buoyancy generated later, and the force applied to the test piece measured by this push force has a minimum value A 'at time t0'.

In this state, if heating is further continued,
As the temperature of the melt increases, the viscosity of the solder base decreases. Due to this decrease in viscosity, the surface tension (that is, cohesive force) of the solder base itself decreases, and the molten solder base floats on the test piece.
Buoyancy occurs. Then, as the temperature rises, the immersion of the test piece into the solder base progresses as the viscosity further decreases, the buoyancy further increases, and the buoyancy and the gravity balance at time t1 until the zero line is reached (see point B). .

From this state, if heating further proceeds,
The viscosity of the solder base further decreases, and the affinity of the solder base for the metallic conductive pattern portion of the test piece increases. As a result, wetting of the test piece to the metal conductor pattern by the solder base proceeds.

Time when the zero line is crossed (t1)
From time t2, the time t2 until the generation of a force that is 0.632 times the force Fmax (see point D) measured in the saturated state of the wetting (wetting described later) is defined as the wetting time T1.

The above is one test piece, for example, test piece 21
However, in the configuration according to the present embodiment, the same acting force acts on the test pieces 21a and 21b, and as described above, the difference between the conductive patterns of the test pieces 21a and 21b is the same as the test piece 21a. The conductive pattern 21a-2 of the test piece 21b protrudes above the solder paste melting surface, and the difference is that the conductive pattern 21b-2 of the test piece 21b does not protrude above the solder paste melting surface.

Therefore, since a force acting on the protruding portion is applied to the test piece 21a more than the test piece 21b, the surface tension can be detected as a difference between the force acting on the test pieces 21a and 21b. Become.

As described above, the wetting of the test piece by the solder base on the metal conductor pattern portion depends on the cohesive force of the liquefied solder base itself and the surface tension generated between the solder base and the flat conductive metal surface. It is described as a contradiction, and among the van der Waals forces is mainly due to the dispersion effect.

The liquefied solder base wets the conductive metal surface to a height balanced with its own cohesive force and rises upward. As a result, the solder base adheres to the metal conductor pattern due to the wetting force from the solder base molten surface to the upper part of the metal conductor pattern, but adheres to the metal conductor pattern due to the cohesive force of the solder base at the molten surface height. The force that is drawn downward acts on the portion that has been drawn.

As a result, a downwardly applied force acts on the test piece, and the acting force measured by the electronic balance increases. This increase in the acting force can be regarded as a component corresponding to the wetting force.

When the same solder base is used and under the same melting temperature condition, the wettability of the solder base to the metal conductor pattern depends on the solder affinity of the metal conductor portion. It depends on the surface properties of the metal conductor pattern, for example, the state of formation of the oxide film, the deposition of impurities on the surface of the conductor pattern, the attachment of impurities to the surface of the conductor pattern, and the surface roughness such as surface roughness.

Therefore, if the wettability of the solder-based metal conductor pattern measured by the inspection is large, the surface condition of the metal conductor pattern is good, and the printed circuit board is considered to be excellent. it can.

In addition to the above, the test pieces 21a and 21a
By providing various differences in the shape / dimensions of the conductive pattern b, it is possible to separate various forces.

[0048]

As described in detail above, claim 1 of the present invention
Since the method for testing the solderability of electronic components according to the present invention is configured to cancel out the measured values of the two test pieces, components other than surface tension, for example, buoyancy and other noise components are offset, and these forces are removed. This has an effect that the influence on the surface tension measurement can be eliminated, and the solderability of the electronic component can be evaluated.

In the method for testing the solderability of an electronic component according to the second aspect of the present invention, the electronic component is used as a printed wiring board. Also, the solderability test method of the present invention can be effectively applied.

The apparatus for testing solderability of an electronic component according to claim 3 of the present invention is configured to cancel out the measured values of two test pieces. Can be canceled, and the influence of these forces on the surface tension measurement can be eliminated. As a result,
It becomes possible to evaluate the solderability of the electronic component.

The electronic component solderability test apparatus according to claim 4 of the present invention uses the electronic component as a printed wiring board, and particularly for a printed wiring board having a large area and a large variation in position. This also has the effect of enabling measurement using the solderability test apparatus of the present invention.

As described above, according to the present invention, it is possible to quantitatively and highly accurately evaluate the solderability of an electronic component, particularly, a printed wiring board used for mounting. As a result of being able to quantitatively evaluate the processing effect, it can be used not only for analyzing the processing effect, but also for receiving inspection of a printed wiring board and failure analysis of a mounting process.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of a solderability test apparatus according to the present invention.

FIG. 2 is a front view showing a configuration example of one test piece.

FIG. 3 is a side view of the test piece of FIG. 2;

FIG. 4 is a front view showing a configuration example of the other test piece.

FIG. 5 is a side view of the test piece of FIG. 4;

FIG. 6 is a diagram showing a change curve of an acting force applied to one test piece when the evaluation apparatus shown in FIG. 1 operates.

[Explanation of symbols]

10 solderability tester, 11a electronic balance, 11b
... Electronic balance, 12a ... Test piece holding means, 12a-1 ... Chuck, 12a-2 ... Slide shaft, 12a-3 ...
Electromagnetic clutch, 12b ... Test piece holding means, 12b-1 ...
Chuck, 12b-2 ... Slide shaft, 12b-3
... electromagnetic clutch, 13 ... micro crucible (solder paste mounting part), 13a ... solder paste, 14 ... heater (heating means), 15 ... drive device, 16a ... detection circuit, 16b
... Detection circuit, 17 ... Difference circuit, 21a ... Test piece, 21a
-1: insulating substrate, 21a-2: conductive pattern portion, 21
a-3: Micro gap, 21b: Test piece, 21b-
DESCRIPTION OF SYMBOLS 1 ... Insulating substrate, 21b-2 ... Conductive pattern part, 21b
-3: Micro gap.

Claims (4)

[Claims] 1. A conductive pattern part of an electronic component is provided at a lower end, and two test pieces having at least a lower end of the same size are used. The shape of the conductive pattern part of the two test pieces is the lower end of one of the test pieces. And the other test piece is formed short from the lower end. The two test pieces are respectively suspended by two external force detecting means, and the lower ends of the suspended two test pieces are solder paste. The solder paste is allowed to enter into the solder paste placed in an unmelted state on the mounting portion, and is supported so as to form a predetermined amount of micro gap from the surface of the solder paste mounting portion, and then the solder paste is heated and melted. The lower end of each of the two test pieces is immersed in the molten solder paste, and only the long conductive pattern portion of the two test pieces protrudes from the solder paste liquid surface. Detecting a force generated between the solder paste and the two test pieces using a detecting unit, and evaluating solderability based on a difference between forces applied to the two test pieces. Test method for soldering of electronic components. 2. The method for testing solderability of an electronic component according to claim 1, wherein said electronic component is a printed wiring board. 3. Two test piece holding means for holding two test pieces each having a difference in the shape of the conductive pattern portion of the electronic component, and two test pieces each supporting the two test piece holding means. A base external force detecting means, a solder paste mounting part on which solder paste is mounted, a support mechanism capable of adjusting a distance between each of the test piece holding means and the solder paste mounting part, and heating the solder paste Heating means for measuring the buoyancy and surface tension acting on the two test pieces based on the two types of output signals from the external force detecting means, and detecting the difference to obtain solder wetting of the test pieces. An electronic component solderability test apparatus characterized in that the solderability can be measured. 4. The apparatus according to claim 3, wherein the electronic component is a printed wiring board.