JPH09145589A - Method and apparatus for testing of solderability of electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus, for testing of the solderability of an electronic component, which correspond to a surface mounting operation and to a bare chip mounting operation and by which the solderability of the electronic component such as, e.g. a printed-circuit board or the like can be evaluated quantitatively and with high accuracy. SOLUTION: The lower end of a test piece 21 such as an electronic component is immersed in a solder paste 13a, the test piece is supported so as to have a microgap in a prescribed amount with reference to the surface of a solder-paste mounting part 13, and the solder paste 13a is heated and melted. The, surface tension which is generated between the molten solder paste 13a and the test piece 21 is detected by an external-force detection means 11. By an output signal from the external-force detection means 11, a change in a force acting on the test piece 21 in which a printed-circuit board or the like is formed to be slender in a rectangular shape is measured, the solder wetting time and the solder wetting speed of the test piece 21 are detected, and its solderability is evaluated quantitatively.

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 testing solderability of electronic components for evaluating the solderability (wetting) of solder, for example, solder paste of electronic components.

[0002]

2. Description of the Related Art Conventionally, various methods have been proposed and standardized for evaluating the solderability of molten solder to, for example, a printed circuit board.
These methods include, for example, a solder wetting and spreading method, various dipping methods, a contact angle method, and the like, all of which qualitatively evaluate the solderability. Further, there is a meniscograph method as a method for quantitatively evaluating the solderability of the insertion mounting component. This cannot be applied to solder paste of surface-mounted components or printed circuit boards.

However, in all of these qualitative evaluation methods of solderability, the evaluation is performed subjectively, and therefore, there are individual differences among operators who perform the evaluation, and also depending on the measuring method and the measuring apparatus. There was a problem that a difference easily occurred. In particular, the meniscograph method has a problem that it is not possible to measure the solderability of surface mount component materials such as solder paste and chip components as well as printed circuit boards.

Further, in recent years, various electronic devices (for example, mobile phones, portable video cameras, etc.) have been sought to be light in weight and small in size, so that high density mounting has been demanded. Along with this, mounting of various electronic components has shifted from conventional insertion mounting to surface mounting. For this reason, the soldering method has changed, and the soldering area has been significantly reduced. Furthermore, in order to improve productivity, the number of defective soldering points should be controlled from several ppm to several tens of p.
It is required in the pm order, and with the enforcement of the PL law, the reliability of the soldered joint is required to be guaranteed for 10 years.

Therefore, it is more strictly required to judge and control the solderability of the printed circuit board due to the method of treating the surface of the copper foil of the electronic circuit board, the variation in the manufacturing process, and the like. The management of deterioration prevention is also becoming important.

[0006]

In the conventional insertion mounting, the soldering to the through holes and the soldering to the relatively large land are the mainstreams. Therefore, for example, the solderability of a printed circuit board is qualitatively evaluated. It was practical and sufficient for practical use. However, in today's demand for high-density mounting and high yield, it is difficult to accurately evaluate solderability by the conventional qualitative evaluation of solderability, which is why surface mounting and future mainstream There is a problem that bare chip mounting, which is presumed to be, cannot be supported.

In view of the above points, the present invention is capable of quantitatively and highly accurately evaluating the solderability of an electronic component such as a printed circuit board in correspondence with surface mounting or bare chip mounting. It is an object of the present invention to provide a solderability test method and device.

[0008]

According to the present invention, the above object is to provide an electronic component such as a printed board suspended by an external force detecting means with respect to a solder paste mounting portion on which the solder paste is mounted. The lower end of the test piece is dipped in the solder paste, supported so as to have a predetermined amount of microgap with respect to the surface of the solder paste mounting portion, and heated, whereby the solder is detected by the external force detecting means. In the solderability test method for electronic parts, which is adapted to detect the surface tension generated between the paste and the test piece, based on the output signal from the external force detecting means, for example, a thin strip-shaped print The force acting on the test piece such as the substrate is measured, and the change in the detected surface tension causes the solder wetting time and solder wetting of this solder paste and the test piece. By detecting is by soldering resistance test method of the electronic component, characterized in that the evaluation of solderability quantitatively, is achieved.

Further, according to the present invention, the above object is to provide an external force detecting means for supporting the test piece holding means, a test piece held by the test piece holding means, and a solder paste mounting the solder paste. In a solderability test apparatus for electronic parts, which comprises a support member for supporting the mounting portion and a heating means arranged in the vicinity of the support member, a test is performed based on an output signal from the external force detection means. This is achieved by a solderability test apparatus for electronic parts, which is provided with a detection circuit for measuring the surface tension of the solder acting on the piece to detect the solder wetting time of the test piece.

According to the above construction, the surface tension due to the molten solder between the test piece of the electronic component to be soldered and the solder paste mounting portion is detected by the external force detecting means. Then, the wetting time for soldering the test piece is detected based on the output signal from the external force detecting means. The length of this wetting time allows the solderability to be evaluated quantitatively and accurately. That is, the shorter the wetting time for soldering, the better the wettability for soldering.

When the above-mentioned test piece or solder paste has the same structure as the electronic component or solder actually used and is hung by the test piece holding means, the surface mounting or bare chip mounting of the actual electronic component is required. The model is modeled under the same conditions as the case, and the solderability of the solder paste and the electronic component is evaluated under this condition, and more accurate evaluation of the solderability is performed.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will now be described in detail with reference to FIGS.
The embodiment described below is a preferred specific example of the present invention, and thus various technically preferable limitations are added. However, the scope of the present invention particularly limits the present invention in the following description. The embodiment is not limited to these embodiments unless otherwise stated.

FIG. 1 shows an embodiment of the solderability test apparatus according to the present invention.
Reference numeral 0 denotes an electronic balance 11 serving as an external force detecting means, a test piece holding means 12, a solder paste mounting portion such as a micro crucible 13, and a melting member acting as a heater disposed below the micro crucible 13. It has a solder bath (heating means) 14. Then, a drive device 15 as a support means for moving the micro crucible 13 up and down.
And a detection circuit 16 to which a signal from the electronic balance 11 is input
It also has.

The electronic balance 11 is fixed and held, and an output signal of the electronic balance 11 is input to an external processing device (not shown) so that a change in acting force can be recorded.

The test piece holding means 12 holds a chuck 12a for holding a test piece 21 for a solder wettability test, an extendable slide shaft mechanism 12b for supporting the chuck 12a, and a lock for the slide shaft mechanism 12b. It is composed of an electromagnetic clutch 12c. The upper end of the slide shaft mechanism 12b of the test piece holding means 12 is suspended from the electronic balance 11.

A predetermined amount of solder paste is placed on the micro crucible 13. Instead of the micro crucible 13, for example, a printed board on which a predetermined amount of solder paste is placed may be used.

Further, the molten solder bath (heating means) 14 acting as a heater is controlled by a control means (not shown) so as to heat the micro crucible 13 and maintain the solder paste in a molten state at a constant temperature. Has become.

The detection circuit 16 detects the wetting time based on the detection signal from the electronic balance 11, for example, draws a working force change curve based on the detection signal from the electronic balance 11, and The change is configured to read the wetting time.

2 to 5 show examples of the structure of the test piece 21 held by the test piece holding means 12. 2 to 5, the test piece 21 has the same structure as that of a printed circuit board actually used, and includes an insulating substrate 21a formed in a strip shape in a vertically long shape, and a surface near a lower end of the insulating substrate 21a. And a conductive pattern 21b formed on the substrate. By making the strip shape like this, the insulating substrate 21a is formed.
The volume of can be reduced and buoyancy proportional to this can be reduced. That is, the buoyancy acting on the insulating substrate 21a immersed in the molten solder can be reduced from the Archimedes principle. The test piece 21 has, for example, a width w of 0.5 to 2 mm, a thickness t of 0.8 to 1.6 mm, a length L1 of about 10 mm, and a conductive pattern 21b having a length L2 of 0.2. It is formed to about 2 mm, but it is not limited to this size, and it is obvious that other sizes may be formed. Further, the conductive pattern 21b may be formed not only on one surface of the insulating substrate 21a but also on both surfaces as shown in FIG. In this way, the conductive pattern 2 on both sides
The substrate on which 1b is formed is called a double-sided substrate.

As shown in FIGS. 6 and 7, the test piece 21 has a conductive pattern 23 formed on the surface near the lower end of a relatively large printed circuit board 22 and V along a cutting line 24 shown by a dotted line. Form cuts and perforations. As a result, each test piece 21 is easily cut along the cutting line 24. Further, in the case of a single-sided substrate, a large buoyancy is generated between the test piece 21 and the molten solder, which makes it difficult to perform a quantitative evaluation. Therefore, a notch as shown in FIG. 3 is provided on the back surface of the conductive pattern 21b.
By providing the notch in this way, the volume of the insulating substrate 21 immersed in the molten solder can be reduced to 1/2, and the buoyancy is also reduced to 1/2. On the other hand, in the case of the double-sided board as shown in FIG. 5, since the conductive patterns 23 are formed on both sides, the surface tension is double that of the single-sided board. Therefore, in the case of a double-sided substrate, it is not necessary to provide a notch if the volume is made small by making it a strip.

The test strip 21 can also be constructed as shown in FIGS. 8 and 9, or 10 and 11.
In FIG. 8 and FIG. 9, the test piece 25 is formed on the surface of the insulating substrate 25a, which is formed in a strip shape in a vertically long shape, and the surface near the lower end of the insulating substrate 25a, as in the case of the test piece 21 of FIGS. The conductive pattern 25b is formed. In this case, as shown in FIGS. 8 and 9, the conductive pattern 25b has its periphery framed by the solder resist 26, and is configured in the same manner as a narrowing land in an actual printed circuit board.

10 and 11, the test piece 27 is, like the test piece 21 of FIGS. 2 to 5, an insulating substrate 27a formed in a vertically elongated strip shape, and a lower end of the insulating substrate 27a. Conductive pattern 27 formed on the surface in the vicinity
b. In this case, the conductive pattern 27b is, as shown in FIGS. 10 and 11, over the entire surface thereof,
Surface treatment 27c is applied. This surface treatment is for rust prevention, and is, for example, pre-slux coating or gold flash plating (thickness of about 0.1 to 0.4 μm), but other surface treatment may be used.

Further, as shown in FIG. 12, the chuck 12a of the test piece holding means 12 is provided with a mounting portion 12d mounted on the slide shaft mechanism 12b of the test piece holding means 12 provided at the upper end and at the lower end. The fixed portion 12e on one side is provided with a movable portion 12g that is moved toward or away from the fixed portion 12e by rotation of the screw 12f. Thus, the upper end of the test piece 21 is inserted between the fixed part 12e and the movable part 12g, and the test piece 21 is clamped and held by the fixed part 12e and the movable part 12g by tightening the screw 12f. Will be.

The chuck may be constructed as shown in FIG. In FIG. 11, the chuck 28
Has a mounting portion 28a mounted on the slide shaft mechanism 12b of the test piece holding means 12 provided at the upper end, and a supporting portion 28b mounted by a screw or the like so as to extend downward from the mounting portion 28a. . Further, a movable portion 28e biased by a spring 28d to approach one side fixed portion 28c fixed to the lower end of the support portion 28b is also provided. That is, when the test piece 21 is held by the chuck 28, the operation is performed as follows. First, the upper end of the movable portion 28e is pushed toward the lower end of the support portion 28b to open the movable portion 28e and the fixed portion 28c, and the upper end of the test piece 21 is inserted therebetween. After that, when the upper end of the movable portion 28e is released, the movable portion 28e moves to the spring 28d.
The lower end of the test piece 21 is pressed against the lower end of the fixed portion 28c by the tension of the test piece 21, and the test piece 21 is sandwiched and held by the fixed portion 28c and the movable portion 28e.

The solderability test apparatus 10 according to the embodiment of the present invention is configured as described above. The solderability tester 10 tests the solderability as follows. First, the test piece holding means 1
2 holds a test piece 21 for a solder wettability test, and a certain amount of solder paste 13a is placed in the micro crucible 13.

From this state, the driving device 15 moves the micro crucible 13 upward. As a result, the lower end of the test piece 21 is moved to the solder paste 13a inside the micro crucible 13 while the micro crucible 13 is moving.
To contact the surface of the micro crucible 13. After that, as the micro crucible 13 rises, the micro crucible 13 pushes up the test piece 21.

As a result, the slide shaft mechanism 12b of the test piece holding means 12 is shortened by the amount by which the test piece 21 is raised, and when the rise of the micro crucible 13 is stopped, the slide shaft mechanism 12b is locked by the electromagnetic clutch 12c. It

In this state, the lower end of the test piece 21 is located on the upper surface of the micro crucible 13, which is a so-called zero level, and the driving device 15 causes the micro crucible 13 to have a so-called micro gap, for example, several tens of μm or more. Hundreds of μ
It is lowered by m. Thus, a micro gap having a predetermined size is formed between the lower end of the test piece 21 and the upper surface of the micro crucible 13.

At this time, since the weights of the test piece holding means 12 and the test piece 21 are applied as a load to the electronic balance 11, this load is reset as a tare and set to zero.

Thereafter, the molten solder bath (heating means) 14 acting as a heater is raised to raise the micro crucible 13
The micro crucible 13, the solder paste 13a, and the test piece 21 are heated by bringing them into contact with the bottom surface of the. A low melting point (about 60 ° C.) metal alloy is melted in a solder bath by a molten solder bath (heating means) 14 that acts as a heater.
Use after it becomes liquid. Thus, the solder paste 13a placed on the micro crucible 13 is
Molten solder bath (heating means) 14 acting as a heater
Contacts the bottom surface of the micro crucible 13 and is instantly heated to a set temperature and melted. At this time, the temperature of the liquid metal is set to the heating temperature, and in this case, the wetting behavior in the instantaneous heating mode is observed. In the process of melting the solder paste 13a, acting forces such as buoyancy and wetting force generated between the solder paste 13a and the test piece 21 are generated as shown in FIG. These forces are detected by the electronic balance 11 and output as electric signals. The temperature of the liquid metal may be set near the melting point, and after contacting the bottom surface of the micro crucible 13, the liquid metal may be heated to the set temperature.
In this case, the wetting behavior of the cream solder during the heating (temperature rise) process can be observed.

According to the change in the acting force (surface tension) thus detected by the electronic balance 11 (see FIG. 14), the following states are shown. That is, points A to B indicate the time from when the molten solder bath (heating means) 14 acting as a heater starts to increase in temperature and comes into contact with the bottom surface of the micro crucible 13 to start heating. Further, the points B to C are heated by the molten solder bath (heating means) 14 acting as a heater and the solder paste 13a
Is heated through the micro crucible 13, and the time until the solvent in the solder paste 13a flows out and volatilizes to start melting. Further, points B to C also indicate the time until the solder paste 13a starts to be heated, the solvent is volatilized, the flux is activated, the surface of the sample is cleaned, and the solder paste 13a starts melting. . Points C to D indicate the time from the start of melting of the solder paste 13a to the wetting of the test piece 21 until the buoyancy of the solder paste 13a acting on the sample and the surface tension are balanced (zero cross). Furthermore, points D to F indicate the time from the occurrence of wetting to the completion.

Here, the change of the acting force is from the point C to the point D, with the residual acting force such as the adhesive force due to the flux in the solder paste 13a acting on the test piece 21 by the molten solder paste 13a. Shows the buoyancy acting on the, and from the point D to the point E, the acting force changes from the buoyancy decrease due to the wetting force of the cream solder 22 to the electrode portion 21a of the metal piece 21 to the equilibrium state.

The detection circuit 16 reads points B and E of the acting force change curve on the basis of the thus obtained change in acting force to obtain the total time from point B to point E, that is, the wetting time. Desired. This operation is performed, for example, by drawing a graph of the change in the acting force and determining the points B and E based on the graph. In addition, in the case of measuring the secular change of solderability, the test piece 21 is put into a steam pressurizer to forcibly cause aging deterioration, and then the wetting time is set by the above-described method. By asking for it, the secular change in solderability will be evaluated.

As described above, according to the present embodiment, in the case of the one-sided substrate, the test piece 21 is thin in a strip shape, and the notch is formed on the back surface of the conductive pattern 23, and the conductive pattern 23 is provided only near the lower end. It will be equipped with. And
In order to produce a strip-shaped test piece 21 having a conductive pattern 23 only near the lower end of the test piece 21, the test piece 21 is formed into a large size and then cut into a predetermined strip shape. Will be done. Therefore, the test piece 21 is easily manufactured at a relatively low cost, and the test piece 21 is also manufactured.
Buoyancy due to molten solder acting on
The relationship in which the surface tension is larger than the buoyancy is established, and the surface tension is accurately measured. Further, since the conductive pattern 23 is provided only near the lower end of the test piece 21, heat dissipation due to heat conduction of the test piece 21 is suppressed to a relatively low level. Therefore, the test piece 21 is easily heated, and thereby the wettability of soldering is accurately generated. Further, in the conventional meniscograph method, because it is a method of immersing the test piece in a pre-melted solder bath, buoyancy acts before the surface tension acts to repel the test piece from the solder bath, It does not produce enough solder wetting and surface tension that is worth measuring. However, according to the present embodiment, after the test piece is immersed in the solder paste 13a in advance and the solder is heated and melted, the flux in the solder paste solder paste 13a is activated before the solder is melted. The surface of the test piece is cleaned. In addition, the temperature of the test piece is also increased by this heating.
The temperature is high enough to start solder wetting. Therefore, the conditions necessary for the start of solder wetting are sufficiently adjusted. Further, simultaneously with the start of melting of the solder, buoyancy proportional to the melting amount of the solder acts on the test piece 21, but solder wetting also starts and a surface tension is generated. Therefore, unlike the above-mentioned meniscograph method, a situation in which solder wetness is hindered by buoyancy does not occur,
Sufficient surface tension measurable is obtained. Since the adhesive force of the solder paste 13a (flux) also acts in the direction of eliminating the adverse effect of this buoyancy, it is convenient at the start of the action of surface tension.

On the other hand, the conductive pattern 25 of the test piece 25
When b is framed by the solder resist 26, when it is formed as a so-called narrowed land, a land having substantially the same shape as the land actually used is provided. Therefore, the actually generated interfacial tension between the printed circuit board and the solder is reproduced more accurately, so that the solderability can be evaluated more accurately.

Further, the conductive pattern 2 of the test piece 27
When 7b is subjected to surface treatment 27c for rust prevention, by preparing a plurality of test pieces with various surface treatments on the conductive pattern 27b, solderability by various surface treatments can be obtained. Changes in the characteristics of can be easily detected. Further, it is possible to measure and evaluate the improvement of solder wettability of surface treatment and the ability to prevent deterioration.

Then, as described above, the test pieces 21, 25,
By forming 27, the surface tension due to the solder paste 13a, which is the molten solder, between the test pieces 21, 25, 27 of the printed circuit board to be soldered and the micro crucible 13 is caused by the electronic balance 11, which is the external force detecting means. To be detected. Based on the output signal from the electronic balance 11, the wetting time for soldering the test pieces 21, 25, 27 is detected, and the solderability is quantitatively evaluated by the length of the wetting time. . Further, by reading the time between D and F from the graph of FIG. 14, it is possible to measure the solder wetting speed of the test pieces 21, 25, 27. Therefore, the solderability can be evaluated easily and accurately in a short time.

In the above-described embodiment, the surface tension between the molten solder in the micro crucible 13 and the test piece 21 detected by the electronic balance 11 is detected to obtain a working force change curve. Although the point B and the point E are obtained from the graph of the acting force change curve and the wetting time is measured, for example, the acting force change curve is input to a computer and the points B and E are analyzed and obtained. Obviously, such software may also allow the wetting time measurement to be processed automatically.

[0039]

As described above, according to the present invention, the solderability of electronic components such as a printed circuit board can be quantitatively evaluated with high accuracy in correspondence with surface mounting or bare chip mounting. Provided are a solderability test method and apparatus for electronic components.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing one embodiment of a solderability test apparatus according to the present invention.

FIG. 2 is a front view showing a first configuration example of a test piece used in the apparatus of FIG.

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

FIG. 4 is a bottom view of the test piece of FIG.

FIG. 5 is a bottom view of a test piece of a double-sided board.

6 is a front view showing a state before being cut into each test piece in the process of manufacturing the test piece of FIG. 2. FIG.

FIG. 7 is a bottom view of the test piece of FIG.

8 is a front view showing a second configuration example of a test piece used in the apparatus of FIG.

9 is a bottom view of the test piece of FIG. 8. FIG.

FIG. 10 is a front view showing a third configuration example of a test piece used in the apparatus of FIG.

11 is a bottom view of the test piece of FIG. 10. FIG.

FIG. 12 is a schematic view showing a first structural example of a chuck used in the apparatus of FIG.

FIG. 13 is a schematic view showing a second configuration example of the chuck used in the apparatus of FIG.

14 is a graph of an action force change curve detected by the solderability test apparatus of FIG.

[Explanation of symbols]

10 ... Solderability test device for printed circuit board, 11
... Electronic balance, 12 ... Test piece holding means, 12a
... Chuck, 12b ... Slide shaft mechanism,
12c ... Electromagnetic clutch, 13 ... Micro crucible, 14 ... Molten solder bath (heating means) acting as a heater, 15 ... Drive device, 16 ... Detection circuit, 21 ... Test piece , 21a ... Insulating substrate, 21b
... Conductive patterns, 22 ... Printed circuit boards, 23 ...
..Conductive pattern, 24 ... Cutting line, 25 ... Test piece, 25a ... Insulating substrate, 25b ... Conductive pattern, 26 ... Solder resist, 27 ... Test piece,
27a ... Insulating substrate, 27b ... Conductive pattern, 2
7c ... Surface treatment, 28 ... Chuck

Claims (9)

[Claims] 1. A lower end of a test piece of an electronic component such as a printed board suspended by an external force detecting means is dipped in the solder paste with respect to the solder paste mounting portion on which the solder paste is mounted. The surface tension generated between the solder paste and the test piece is detected by the external force detecting means by supporting the surface of the solder paste mounting portion so as to have a predetermined amount of microgap and heating. In the solderability test method for electronic parts, based on the output signal from the external force detecting means, the force acting on the test piece thinly formed in a strip shape is measured, and the detected surface tension of Quantitatively evaluate the solderability by detecting the solder wetting time and solder wetting speed of this solder paste and the test piece according to the change. Solderability testing method of the electronic component, characterized. 2. An external force detecting means for supporting the test piece holding means, a test piece held by the test piece holding means, a support member for supporting the solder paste mounting portion on which the solder paste is mounted, and a support. In a solderability tester for electronic parts, which comprises a heating means arranged in the vicinity of the member, the surface tension of the solder acting on the test piece is measured based on the output signal from the external force detecting means. Then, a solderability test apparatus for electronic parts, which is provided with a detection circuit for detecting the solder wetting time of the test piece. 3. The soldering of an electronic component according to claim 2, wherein the test piece has the same structure as a printed circuit board actually used and is vertically suspended by a test piece holding means. Sex testing equipment. 4. The test piece is thinly formed in a strip shape,
The solderability test device for an electronic component according to claim 2, wherein a conductive pattern is provided at one end thereof. 5. A notch is provided in a portion of the test piece where the conductive pattern is not formed so as to reduce the volume of the test piece in the molten solder and reduce the influence of buoyancy acting on the test piece. The solderability tester for electronic parts according to claim 2. 6. The conductive pattern of the test piece is formed as a so-called narrowing land by being framed by a solder resist.
A solderability tester for electronic components as described in. 7. The conductive pattern of the test piece is surface-treated for rust prevention.
A solderability tester for electronic components as described in. 8. The solderability test apparatus for an electronic component according to claim 6, wherein the surface treatment is pre-flux coating or gold flash plating. 9. The solderability test device for an electronic component according to claim 2, wherein the test piece holding means holds the test piece in a fixed manner based on the tightening of a screw or the elasticity of a spring.