JP2003083866A - Testing device of solder paste characteristic and testing method of solder paste characteristic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a testing device and testing method capable of performing the evaluation of wetting characteristic with respect to various solder pastes by use of the same index. SOLUTION: This testing device comprises a heater unit for heating a paste layer consisting of a solder paste to be tested in the state where the lower end of a testing contact member is inserted to the paste layer; a lighting means for lighting a fillet forming spot where a solder filler is to be formed by heating the paste layer; and an image recording means having a visual field facing a section vertical to a paste layer forming surface in the fillet forming spot. This testing method comprises calculating the shape characteristic of the solder paste from the image data of the fillet forming spot by use of the above testing device, and measuring the time required until the shape characteristic is laid in a prescribed stable state from the time of starting the melting of the solder paste or the time of reaching substantially the same temperature as the liquid phase line temperature for the solder paste.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder paste characteristic testing apparatus and a solder paste characteristic testing method for testing the characteristics of a solder paste used for surface mounting electronic components on a printed circuit board, for example. .

[0002]

2. Description of the Related Art In recent years, with the miniaturization and higher functionality of electronic equipment, it has been required to mount small electronic components on a printed circuit board at a high density. The surface mounting method has been adopted as a method for mounting electronic components. In this surface mounting method,
For example, on the connecting electrodes formed on the printed circuit board,
For example, a solder paste is applied by screen printing to form a paste layer, and then electronic components are arranged on the printed circuit board so that the electrodes are located on the paste layer, and in this state, the solder alloy in the paste layer is placed. To reflow. Specifically, by heating / cooling the paste layer according to a preset temperature profile,
The solder alloy in the paste layer is melted and re-solidified, so that the connection electrode of the printed circuit board and the electrode of the electronic component are connected by the solder alloy.

Therefore, in such a surface mounting method, it is extremely important to evaluate beforehand the characteristics of the solder paste to be used, especially the wetting characteristics of the solder paste with respect to the electrodes of the electronic component to be mounted. For example, if the solder paste satisfies the following conditions (1) to (3), the solder paste has “good wettability”. (1) A well-balanced and beautifully shaped fillet is formed in a short time. (2) The contact angle of the solder paste with the electronic component is small. (3) A predetermined amount of wetting force is generated in a short time.

Conventionally, as a method for testing the characteristics of a solder paste, a test contact member is immersed from above in a solder bath that has been heated and melted in advance, and the test contact member is immersed in the immersion direction (vertical direction). A meniscograph method for measuring a change in applied stress over time is known. However,
The meniscograph method is a method for evaluating the wettability of solder in a molten state, not a method for evaluating the wettability of solder paste by reflow. That is,
In the reflow process in the surface mounting method, the solder paste is heated while being in contact with the electrodes of the electronic component, so that the surface temperature of the electrode of the electronic component is always equal to the temperature of the solder paste in the wet process, and , It is considered that the solder alloy in the solder paste is melted while the electronic component is wetted by the molten solder alloy. Wet characteristics cannot be evaluated according to the actual conditions of.

In order to solve such a problem, a test contact member is brought into contact with a paste layer made of a solder paste to be tested to enter a predetermined depth, and the paste layer is set to a preset temperature profile. A solder paste characteristic test method for detecting a change in stress acting in the direction perpendicular to the test contact member (the direction in which the test contact member enters the paste layer) while heating according to
It is called "temperature profile method". ) Has been proposed (see Japanese Patent Laid-Open No. 6-207900). Here, the above temperature profile is set according to the heating conditions of the reflow step in surface mounting, and specifically, for example, a temperature raising step to a preheat temperature, a preheat temperature holding step,
It is composed of a main heating temperature raising step and a main heating peak temperature holding step. In such a temperature profile method, in the process from the start of melting of the solder alloy in the solder paste to the end of the wetting of the test chip by the molten solder alloy, the vertical direction acting on the test contact member By detecting the change in stress, the characteristics of the solder paste can be evaluated.

FIG. 13 is a diagram showing a solder paste characteristic curve measured by the temperature profile method. In this figure, the vertical axis represents the stress acting in the direction perpendicular to the test contact member, the positive direction represents the force (pulling force) that pulls the test contact member downward by the paste layer, and the negative direction. Indicates the force (pushing force) for pushing the test contact member upward by the paste layer. The horizontal axis is the heating time. FIG.
More specifically, in the main heating and heating step, before the solder alloy in the paste layer is melted, as the temperature of the paste layer rises, the paste layer supporting member on which the paste layer is formed is heated. It is deformed, so that a pressing force acts on the test contact member. After that, when the heating temperature of the paste layer is further increased, when the melting of the solder alloy in the paste layer starts, the volume of the paste layer rapidly decreases in the process of the solder alloy converting from the solid phase to the liquid phase. As a result, a pulling force acts on the test contact member (hereinafter, this pulling force is also referred to as "liquid phase conversion force"). The liquid phase conversion force increases as the volume of the paste layer decreases, but as the melting of the solder alloy progresses, the fluidity of the paste layer increases and the liquid phase conversion force attenuates. On the other hand, when the melting of the solder alloy is started, the test contact member starts to be wetted by the melted solder alloy, and the pulling force acts on the test contact member due to the surface tension of the melted solder alloy. This attractive force increases as the wetting progresses, and shows a stable value in a sufficiently wet state.

From the above characteristic curve, for example, the value Fm of the pulling force acting on the test contact member when the test contact member is sufficiently wet by the solder alloy is measured as the maximum wetting force of the solder paste. To do. Further, after the pressing force due to the thermal deformation of the paste layer supporting member acts on the test contact member, the time point ts at which the pressing force decreases and becomes 0, is the time point when the wetting starts (hereinafter, “wetting start point”). "
Say. ), The time point te when the test contact member is sufficiently wet by the solder alloy, that is, the time point te at which the pulling force acting on the test contact member reaches the maximum wetting force (Fm),
When wetting ends (hereinafter referred to as "wetting end point")
Wet start point (ts) to wet end point (te)
The time Tw up to is measured as the wetting time. The values of the maximum wetting force (Fm) and the wetting time (Tw) differ depending on the surface activity of the test contact member, that is, the electrode of the electronic component, the type of flux contained in the solder paste, and the like. It is possible to evaluate the wetting characteristics of the solder paste.

According to such a temperature profile method,
Since the paste layer is heated while the test contact member is in contact with the paste layer, the surface temperature of the test contact member is always equal to the temperature of the paste layer during the wetting process, and the solder in the paste layer is Since the test contact member gets wet with the molten solder alloy as the alloy melts, it is possible to evaluate the wettability according to the actual condition of the reflow process in surface mounting.

On the other hand, the solder paste used for surface mounting has conventionally been mainly composed of a tin-lead eutectic solder alloy, but recently, from the viewpoint of environmental protection, it is lead-free. It is required to use a material containing a solder alloy. However, when the wetting characteristic test of the solder paste containing the lead-free solder alloy is performed by the temperature profile method, it has been found that the following problems occur.

Many lead-free solder alloys are non-eutectic, and such solder alloys have a wide temperature range in their melting points. To give a specific example, the melting point of Sn-37Pb solder alloy is 183 ° C, whereas Sn-2Ag
-0.75Cu-3Bi solder alloy has a melting point of 206-2.
It is 20 ° C. and has a temperature range of 14 ° C. When conducting a characteristic test of a solder paste containing such a solder alloy, Sn-37P is used in the main heating and heating step.
b The melting time of the solder alloy (the time from the start of melting to the end of melting) is theoretically equivalent to the time of absorbing latent heat, so it is constant and short, whereas Sn
The melting time of the -2Ag-0.75Cu-3Bi solder alloy is the time for absorbing the latent heat, plus the time for raising the temperature from the minimum value to the maximum value of the melting point. For example, when the heating rate in the main heating / heating step is set to 3 ° C./sec, the melting time of the Sn-2Ag-0.75Cu-3Bi solder alloy is the time for absorbing latent heat +4.7 seconds. The value is considerably larger than the melting time of the Sn-37Pb solder alloy.

In the temperature profile method,
Since the time from the start of melting of the solder alloy until the test contact member gets wet by the solder alloy is measured as the wetting time, Sn-37Pb solder alloy and Sn-2Ag-
When compared with the 0.75Cu-3Bi solder alloy, even if the true wetting time, that is, the time from the start of wetting of the test contact member by the solder alloy to the end of wetting is equal, the actual wetting time Since the time from the melting of the alloy to the start of wetting of the test contact member by the solder alloy is included as an error, the wetting time measured differs greatly, and in the end, in the temperature profile method, solder alloys with different melting point temperature ranges are used. The fact is that the wetting characteristics of a solder paste containing Pt cannot be evaluated with the same index.

[0012]

The present invention has been made based on the above circumstances, and its purpose is to:
It is an object of the present invention to provide a novel solder paste property test apparatus and a solder paste property test method capable of evaluating the wettability of the solder paste with respect to various solder pastes using the same index.

[0013]

The solder paste property testing apparatus of the present invention comprises a heating chamber, and in the heating chamber, the lower end of the test contact member is placed on the paste layer of the solder paste to be tested. A heater unit for heating the paste layer in a state of being pushed in from the upper surface of the layer, and a light irradiation means arranged to illuminate a fillet formation point where the paste layer is heated to form a solder fillet, and An image recording unit having a field of view facing a section perpendicular to the paste layer forming surface at the fillet forming portion.

In the solder paste property testing apparatus of the present invention, it is preferable that the paste layer is heated according to a preset temperature profile. Further, the light irradiating means is such that when the optical axis thereof is tilted upward by 0 to 60 ° with respect to the plane including the paste layer forming surface and the optical axis is projected onto the plane including the paste layer forming surface. It is preferable that the projection line and the optical axis of the image recording means are arranged at an angle of 0 to 170 °. The light irradiating means irradiates the fillet forming portion with slit light, and the width of the slit light is from 0.001 to 0.001.
It is preferably 2 mm. Further, it is preferable that the temperature detecting means is provided at a position outside the visual field of the image recording means in a state of being pressed into the paste layer.

In the above-mentioned solder paste characteristic testing apparatus, the upper wall of the heater unit is hermetically sealed above the paste layer supporting member which is placed in the heating chamber and which supports the paste layer made of the solder paste to be tested. A stress detection sensor unit having a holding member for holding the test contact member at a predetermined position in the heating chamber, the test contact member being held in the stress detection sensor unit. However, an elevating mechanism for moving the entire heater unit relatively upward may be provided so that the paste layer supporting member is held in a state of having entered the paste layer.

The solder paste characteristic test method of the present invention is
In the heating chamber, the lower end of the test contact member is pressed into the paste layer made of the solder paste to be tested from the upper surface of the paste layer, by heating the paste layer, a fillet forming process for forming a solder fillet. In, in a state in which the paste layer is heated to irradiate the fillet formation point where the solder fillet is to be formed, obtain image data of a cross section perpendicular to the paste layer formation surface at the fillet formation point, Calculate the shape characteristics of the solder paste by image processing the image data, when the solder paste begins to melt, or from the time when the temperature of the paste layer reaches a temperature substantially the same as the liquidus temperature, Measure the time required for the calculated solder paste shape characteristics to reach a predetermined stable state. Characterized in that it.

In the solder paste characteristic test method of the present invention, the shape characteristics of the solder paste calculated from the image data are the contact angle (θ) of the solder paste wetting with respect to the test contact member, the paste layer in the paste layer supporting member. It can be at least one selected from the height (h) of wetting from the forming surface to the upper edge of the solder paste and the cross-sectional area (S) of wetting of the solder paste.

[0018]

According to the present invention, it is possible to directly determine the wet state of the solder paste from the image data of the solder paste which has been heat-treated under the temperature condition to be actually treated. In the process of forming the fillet, the point of time when wetting starts can be specified without causing a large error, and as a result, a universal index for quantitatively evaluating the wettability of the solder paste is obtained. Therefore, the wettability of the solder paste can be evaluated with high reliability and stability regardless of the type of the solder paste.

[0019]

FIG. 1 is an explanatory perspective view showing the appearance of an example of a solder paste characteristic testing apparatus of the present invention,
2 is a cross-sectional plan view showing the outline of the configuration of the solder paste characteristic test apparatus shown in FIG. 1, and FIG. 3 is a vertical cross-sectional view showing the outline of the configuration of the solder paste characteristic test apparatus shown in FIG. This solder paste characteristic testing device includes a box-shaped heater unit 10 having a rectangular parallelepiped shape as a whole, and the heater unit 10 is a front wall that is a front side wall (a side wall located below in FIG. 2). ) Front opening 1
0A is formed, and a side opening 10B is formed on one side wall (a side wall located on the left side in FIG. 2) adjacent to the front wall. In each of the front opening 10A and the side opening 10B in the heater unit 10,
Transparent window members 11A and 11B are provided to hermetically close the openings 10A and 10B from the outside, whereby a heating chamber R is formed inside the heater unit 10.

Reference numerals 12 and 13 are gas supply pipes for supplying, for example, nitrogen gas or air into the heating chamber R, and 14 is for sampling the gas in the heating chamber R and detecting the component concentrations thereof. It is a gas sampling pipe for.

In the heating chamber R, a heater table 25, which is a mounting means for mounting the test strip unit 20, is provided at the central position of the lower surface. The heater table 25 has a lower surface of the test strip unit 20. A planar heater 26 having a heat generating area that covers the entire area is provided so as to extend parallel to the test piece unit mounting surface 25A of the heater table 25. Then, the test strip unit 20 placed on the heater table 25 is heated from below by the planar heater 26 so that the test strip unit 20 is uniformly heated to a predetermined temperature by the heating means described later. The heating state of the single unit 20 is adjusted.

In the test piece unit 20 supported by the heater table 25, the lower end of the test contact member was pushed in from the upper surface of the paste layer by the paste layer supporting member supporting the paste layer made of the solder paste to be tested. The electrode 24A in the electronic component 23, which is a test contact member,
24B is held in a state of being pressed into each of the solder paste layers 22A and 22B formed on the surface of the circuit board 21 which is a paste layer supporting member.

On each of the upper wall and the lower wall of the heater unit 10, an upper heating means 30 and a lower heating means 31, which are, for example, planar heaters, extend in parallel with the test piece unit mounting surface 25A of the heater table 25. By this, the test strip unit 20 is heated from above by the upper heating means 30 and from below by the lower heating means 31.

In front of the heater unit 10, the test piece unit 20 on the heater table 25 in the heating chamber R is provided through a window member 11A provided in the front opening 10A.
CCD camera 3 which is an image recording means having a field of view
5 is installed, and the optical axis P of the CCD camera 35 extends in a direction perpendicular to the window member 11A (vertical direction in FIG. 2). Specifically, the solder paste 22A relating to the one electrode 24A located on the side surface opening 10B side of the heater unit 10, which is a fillet forming portion to be heated by the heating means to form a fillet, is attached to the solder paste 22A of the CCD camera 35. The optical axis P is positioned.

This CCD camera 35 has at least one
It is preferable to mount a telephoto lens 36 such as a microfocus lens which can be magnified 0 times or more. The distance between the CCD camera 35 and the test strip unit 20 is preferably 50 to 200 mm, for example.

Solder for the fillet forming point in the test piece unit 20 supported by the heater table 25 in the heating chamber R, for example, one electrode 24A, through the window member 11B provided in the side opening 10B of the heater unit 10. A light irradiation optical system 40, which is a light irradiation unit, is installed so as to illuminate the central position in the front-rear direction of the paste 22A with band-shaped light. The light irradiation optical system 40 is
As shown in FIG. 4, a light source 41 made of, for example, a laser diode is arranged so that the optical axis Q extends obliquely forward and upward of the heater unit 10, and the light from this light source 41 is CC
It is configured by a first condensing lens 42 made of, for example, a convex lens and a second condensing lens 43 made of, for example, a cylindrical lens, for irradiating in a direction perpendicular to the optical axis P of the D camera 35.

The light source 41 is in a state in which its optical axis Q is inclined upward by 0 to 60 ° with respect to the plane including the paste layer forming surface of the circuit board 21, and in FIG. It is preferable that an angle (hereinafter, referred to as “elevation angle”) β formed by the projection straight line N when Q is projected on a plane including the paste layer forming surface is in a state of 0 to 60 °. Also,
The optical axis P of the CCD camera 35 and the projection line N of the optical axis Q of the light source 41 form an angle (hereinafter referred to as "rotation angle in the horizontal plane") α of 0 to 170 °. Is preferred. Since the light source 41 is installed with the optical axis Q thereof satisfying the above-mentioned three-dimensional angular range, a predetermined cross section at the fillet forming portion of the test piece unit 20 is reliably irradiated with the band-shaped light. Therefore, the image data of the solder paste in the process of forming the fillet can be surely obtained.

In this light irradiation optical system 40, the slit light L is irradiated to the test piece unit 20, and the width of the slit light L is preferably 0.001 to 2 mm (see FIG. 5). However, FIG. 5 shows a state in which the solder paste has finished wetting the electrodes 24A and 24B of the electronic component 23 and a fillet has been formed. As a result, the degree of inclusion of image data that becomes noise due to bubbles or the like generated when the solder paste begins to melt can be reduced, and image data of the solder paste in the fillet formation process can be reliably obtained.

Inside the heating chamber R, there is provided a temperature detecting means 50 for detecting the temperature of the solder paste in the process of forming the fillet. For example, as shown in FIG. 6, the temperature detecting means 50 has a thermocouple 51 having a metal element wire coated with, for example, glass fiber, and a holding member 52 made of, for example, ceramics for holding the thermocouple 51 at a tip portion thereof. However, the base end portion is configured by a leaf spring 54 fixed by a fastener 53 such as a screw, and the thermocouple 51 projects from the lower surface of the leaf spring 54. And
The thermocouple 51 is in contact with a portion outside the field of view of the CCD camera 35, for example, the solder paste 22B related to the other electrode 24B of the electronic component 23 while being biased by the spring force of the leaf spring 54. . Further, the temperature detecting means 55 for detecting the temperature of the circuit board 21 may be further provided.

In the present invention, the characteristic test of the solder paste is conducted as follows using the above-mentioned test apparatus. First, an appropriate amount of solder paste to be tested is applied to a predetermined portion on the surface of the circuit board 21 by using a printing method such as screen printing to form paste layers 22A and 22B. , 22B by pushing the electronic component 23 into a predetermined depth and supporting it by the heater table 25 in the heating chamber R of the heater unit 10 with the paste layer forming surface horizontal. To do.

In the above description, the amount of the solder paste to be applied is such that a well-balanced and beautifully shaped fillet should be formed. For example, the paste layers 22A and 22B are used.
Is preferably 1 to 8 mm, the thickness of the paste layers 22A and 22B is 0.1 to 0.4 mm, and the volume of the paste layers 22A and 22B is 0.01 to 2.0 mm ³ . Here, "a well-balanced and beautiful shape" means
For example, the contact angle θ of the fillet is 0 to 35 °, the wetting height h is 0.2 to 3.0 mm, and the wetting cross-sectional area S is 0.05 to
The shape is 10 mm ² . Paste layers 22A, 22
The push-in depth of the electronic component 23 with respect to B is the paste layer 22.
Depending on the thickness of A and 22B, for example, 0.05 to
It is preferably set in the range of 0.2 mm.

Next, the CCD camera 35 and the light irradiation optical system 40 are installed in a state satisfying a predetermined positional relationship with the test strip unit 20 supported in the heating chamber R, and then one of the electronic components 23 is installed. In the state where the light source 41 illuminates the center position in the front-rear direction in the paste layer 22A (fillet formation point) related to the electrode 24A, the gas supply pipe is used according to the condition of the reflow process in the surface mounting in which the solder paste to be tested is used An inert gas such as nitrogen gas or air from 12, 13 is heated in the heating chamber R.
And heating the paste layers 22A and 22B according to a temperature profile preset according to the heating conditions of the reflow process by the upper heating means 30, the lower heating means 31, and the planar heater 26 in the heater table 25, Paste layer 2 by CCD camera 35
2A is photographed to obtain image data of a predetermined cross section of the solder paste in the fillet formation process. Also,
The temperature detecting means 50 detects the temperature state of the paste layer 22B of the other electrode 24B of the electronic component 23.

FIG. 7 is an explanatory diagram showing an example of a temperature profile for heating the paste layer. In FIG. 7, A is the time of the temperature raising process up to the preheat temperature t1, and the temperature raising rate in this temperature raising process is, for example, 1 to 4 ° C.
/ Sec. B is the time of the preheat temperature holding step, and this time B is, for example, 30 to 150 seconds,
The preheat temperature t1 is set to a temperature lower than the melting point (the minimum value of the solder alloy in the solder paste to be tested in the case of having a temperature range). C is the time of the main heating and heating step, and the heating rate in this heating step is, for example, 1 to 4 ° C./sec. D is the time of the main heating peak temperature holding step, and this time D is, for example, 3 to 10 seconds, and the main heating peak temperature t2 is determined from the melting point of the solder paste (the maximum value in the case of having a temperature range). Is also set to a high temperature.

Here, the state of the paste layer 22A (22B), that is, the electrode 24A (24 in the electronic component 23)
The behavior of soldering of the solder paste with respect to B) will be described. First, the circuit board 21 and the electrode 24A (24A (24) by the preliminary heating process performed in the preliminary heating process (heating process A + preheat temperature holding process B).
As the temperature of B) rises, evaporation of various components contained in the solder paste occurs. Then, by performing the main heating process in the main heating step (main heating temperature raising step C + main heating peak temperature holding step D), the fluidity of the flux contained in the solder paste increases, and the solder alloy begins to agglomerate. After that, when the soldering temperature is approached, the flux increases its activity and the circuit board 21 and the electrodes 24
While cleaning A (24B), the solder alloy starts to melt to increase cohesive force and start wetting. Then, as the wetting progresses, the size of the contact angle θ decreases, and the height h of the wetting and the size of the cross-sectional area S of the wetting increase, so that these shape characteristics finally reach a predetermined stable state. The wetness ends.

By performing image processing on the image data obtained as described above, the paste for calculating the shape characteristic of the paste layer 22A and for obtaining the characteristic curve showing the change with time of the obtained shape characteristic A property acquisition operation is performed. Specifically, for example, the image data obtained by the CCD camera 35 is subjected to appropriate image processing to simulate the state of the solder paste in the fillet forming process as shown in FIG. 8B, for example. After being converted into the analysis image data shown, as shown in FIG. 9, the shape characteristics of the contact angle θ of the paste layer 22A with respect to the electrode 24A in the electronic component 23, the wet height h, and the wet cross-sectional area S are calculated. As shown in FIG. 8A, the shape characteristic curve of the solder paste during the fillet formation process (see FIG.
It is visually displayed on a monitor (not shown) as a curve A) in (a). The values of the contact angle θ, the wetting height h, and the wetting area S shown in FIG. 8 are numerical examples at the time indicated by the broken line in FIG.

From the viewpoint of improving the time efficiency of image processing and improving the reliability of data, it is preferable to perform such paste characteristic acquisition operation at intervals of, for example, 10 to 66.6 msec. Also, the paste characteristic acquisition operation is
Although it may be performed only for at least one shape characteristic selected from the contact angle θ of the solder paste, the wetting height h, and the wetting cross-sectional area S, the index for evaluating the solder paste is highly reliable. Since it is obtained, it is preferable to perform all of these shape characteristics.

Further, the temperature characteristic curve (curve B in FIG. 8A) showing the change over time of the temperature state of the paste layer 22B relating to the other electrode 24B detected by the temperature detecting means 50 is the shape of the solder paste. The characteristic curves can be displayed at the same time.

Then, from the above-mentioned image data for analysis and the shape characteristic curve of the solder paste, the time point (T0 in FIG. 8 (A)) at which it is confirmed that the solder paste has started to melt is regarded as the wetting start point, and In the solder paste characteristic curve, when the contact angle θ, the wetting height h, and the cross-sectional area S of wetting all the shape characteristic values reach the final stable state (T1 in FIG. 8A), the wetting end point is set. Regarded, the time from the wet start point to the wet end point (hereinafter,
It is called "fillet formation time". ) T is calculated, and the wetting characteristics of the solder paste are evaluated based on the value of the fillet formation time T. Specifically, the fillet formation time T is calculated by calculating the time from the wetting start point to the final stable state for each shape characteristic and taking the average value of the obtained values. In the above description, the final stable state of the paste layer in the fillet formation process means that the variation range of the contact angle θ, the wetting height h, and the wetting cross-sectional area S in the shape characteristic curve of the solder paste is ± 0. It is a state at a time one second before the time when it is determined that the speed is less than or equal to 05 × (θ, h, S) / sec.
Also, the time (T0) when the solder paste begins to melt is
It is determined based on the temperature data obtained by the temperature detecting means 50.

Further, the time when the temperature of the solder paste detected by the temperature detecting means 50 reaches substantially the same temperature as the liquidus temperature of the solder paste is regarded as the wetting start point, and the fillet formation time is determined. You may calculate T. In addition, "substantially the same" means the temperature detecting means 5
It means that the temperature of the solder paste detected by 0 coincides with the liquidus temperature within a temperature range of ± 1 ° C.

According to the test apparatus as described above, it is possible to directly judge the wet state of the solder paste from the image data of the solder paste which has been heat-treated under the temperature condition to be actually treated. Therefore, in the process of forming the fillet, it is possible to specify the time when the wetting is started without causing a large error,
As a result, it is possible to obtain a universal index for quantitatively evaluating the wettability of the solder paste. That is, in the fillet formation process, the time when the solder paste, which is regarded as the wetting start point of the solder paste, starts to melt,
Substantially, the temperature of the solder paste has reached a temperature state that coincides with the liquidus temperature at which the solid phase is converted to the liquid phase, and therefore, from the time when the solder paste begins to melt to the final stable state. By calculating the fillet formation time, it is possible to actually evaluate the characteristics of the solder paste in the process of wetting the test contact member, which makes it possible to reliably and stably evaluate the solder paste wetting characteristics. Can be done on a regular basis.

FIG. 10 is an explanatory sectional view showing the outline of the configuration of another example of the solder paste characteristic testing apparatus of the present invention. In this solder paste property testing device,
A stress detection sensor unit 60 for detecting the stress acting on the electronic component 23 by the paste layers 22A and 22B is provided, and the stress detection sensor unit 60 is provided with a heater above the position where the test piece unit 20 is to be supported. The support rod 61 that vertically extends through the upper wall of the unit 10 and extends in the vertical direction, the stress detection sensor 62 connected to the upper end of the support rod 61, and the electronic component 23 connected to the lower end of the support rod 61. A holding member 63 that holds the heating chamber R at a predetermined position is provided.

On the lower wall of the heater unit 10, at the center position of the lower surface thereof, the entire heater unit 10 is vertically moved so that the circuit board 21 supported in the heating chamber R is held at a predetermined position. A mechanism 65 is provided. The elevating mechanism 65 has a rotary drive shaft 66 whose upper end is connected to the lower surface of the heater unit 10 and is arranged so as to extend in the vertical direction. The rotary drive shaft 66 has a drive source 67 which is, for example, a stepping motor. Are connected.

Other configurations are the same as those of the solder paste characteristic testing apparatus shown in FIGS. 1 to 3, and the same components are designated by the same reference numerals.

In such a test apparatus, basically, the paste layers 22A, 22A,
While heating 22B, the state of the paste layer 22A is photographed by the CCD camera 35 to obtain image data of a predetermined section of the solder paste in the fillet formation process,
The shape characteristics of the solder paste are calculated by performing image processing on the obtained image data, and the wetting characteristics are evaluated by the solder paste characteristics (fillet formation time) calculated based on the shape characteristics. However, the CCD camera 35 acquires the image data of the solder paste, and the stress detection sensor unit 60 detects the change in the stress acting on the electronic component 23 in the vertical direction (vertical direction).

Specifically, the paste layers 22A and 22B are formed by applying a solder paste to be tested to predetermined portions on the surface of the circuit board 21, and the circuit board on which the paste layers 22A and 22B are formed. 21
While supporting the electronic component 23 at a predetermined position in the heating chamber R and holding the electronic component 23 by the holding member 63 of the stress detection unit 60, the lifting mechanism 65 moves the entire heater unit 10 upward, and the electronic component 23 is When the paste layers 22A and 22B are brought into contact with each other, the stress due to the contact is detected by the stress detection sensor 62, so that the movement of the heater unit 10 is temporarily stopped, and then the elevating mechanism 65 moves the heater unit 10 by a predetermined distance. . As a result, the electronic component 23 comes into contact with the surfaces of the paste layers 22A and 22B and penetrates to a predetermined depth, and further, the distance between the interface between the electronic component 23 and the paste layers 22A and 22B and the surface of the circuit board 21. Is held constant.

Then, a temperature profile preset according to the heating conditions in the reflow process in the surface mounting in which the solder paste to be tested is used (see FIG. 7).
While heating the paste layers 22A and 22B in accordance with the above, the stress detection sensor 62 detects a change in stress acting in the vertical direction (vertical direction in FIG. 10) with respect to the electronic component 23, and thus the wetting force of the solder paste is A characteristic curve is obtained (see FIG. 13). Then, the wetting force characteristic curve of the solder paste is visually displayed on a monitor (not shown) in association with the shape characteristic curve acquired from the image data.

According to the test apparatus as described above, basically, the wet state of the solder paste is directly determined from the image data of the solder paste which is actually heat-treated under the temperature condition to be treated. In the process of forming the fillet, it is possible to specify the time when wetting is started without causing a large error, and as a result, the wettability of the solder paste is quantitatively evaluated. It is possible to obtain a universal index for this, and thereby, the wetting characteristics of the solder paste can be stably evaluated with high reliability. Moreover, the electronic component 23
By detecting the change in stress acting on
In addition to the evaluation of the wettability by the fillet shape, the evaluation of the wettability of the solder paste can be realized from the change as the physical quantity, and therefore the reliability of the evaluation can be further enhanced.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described modes, and various modifications as described below can be added. For example, in the above embodiment, the case where the electronic component used for mounting is used as the test contact member and the circuit board used for mounting is used as the supporting member for supporting the solder paste has been described as an example. Instead of the electronic components and the circuit board used for mounting, a substitute such as a metal plate can be used.

Further, for example, an electronic component 70 having an L-shaped lead terminal (L lead; gull wing) 71 shown in FIG. 11 and a J-shaped lead terminal (J lead) 76 shown in FIG. 12 are provided. When the electronic component 75 is used as a test contact member, the top fillet 80 and the protruding direction of the lead terminals 71, 76 to be formed on the outer side of the protruding direction of the lead terminals 71, 76 (left side in the drawing). The solder paste characteristics of both the heel fillets 81 to be formed on the inner side of are evaluated based on the shape characteristics obtained from the image data. In FIGS. 12 and 13, 72 is a pad on which a paste layer is applied and formed.

[0050]

EXAMPLES Hereinafter, specific examples of the solder paste characteristic test method of the present invention will be described, but the present invention is not limited to these examples.

The following were prepared as the solder paste. Paste 1: RMA (Moldly activate)
Drosin base) -based flux containing powdered Sn-37Pb solder alloy (melting point 183 ° C.), paste 2: RMA (Moldly activate)
Solder paste in which powdered Sn-3.5Ag-0.75Cu solder alloy (melting point 217 to 219 ° C) is contained in a flux based on drosin base, Paste 3: RMA (Moldly activate)
a solder paste containing a powdered Sn-2Ag-0.75Cu-3Bi solder alloy (melting point 206 to 220 ° C.) in a flux based on drosin base),

<Example 1> Using the solder paste characteristic test apparatus manufactured according to the configuration shown in FIG.
A solder paste characteristic test was conducted according to the following conditions, and the solder paste shape characteristics shown in Table 1 below were obtained. In Table 1 below, the calculation results of the shape characteristics of the solder paste are shown at intervals of 0.5 seconds, with the time when the solder paste starts to melt as 0 sec. Such a paste characteristic test was conducted 5 times each, and the average value of the fillet formation time based on the image data was obtained. The results are shown in Table 2 below.

[Paste Layer Support Member] Material: Phosphorus deoxidized copper (C1201P), Dimension: 25 mm ×
31 mm × 0.3 mm [Test contact member] Test contact member: A copper plate having a width of 3 mm, a length of 10 mm and a thickness of 0.3 mm, which is surface-cleaned by being immersed in a 5% hydrochloric acid aqueous solution for 60 seconds. [CCD camera and light irradiation optical system] 4 in CCD camera
With a microfocus lens that can be magnified 0 times,
The paste layer in the heating chamber was set in a state capable of photographing at 20 times the telephoto, and the CCD camera was arranged in a state of being separated from the photographing section of the solder paste by 150 mm.
A laser diode is used as a light source that constitutes the light irradiation optical system, and the rotation angle (α) in the horizontal plane with respect to the optical axis of the CCD camera is set so that the slit light from the light source is irradiated to the central position in the thickness direction of the test contact member. The light irradiation optical system was arranged at 90 ° and an elevation angle (β) of 45 °.

[Test Conditions] A paste layer having a diameter of 8 mm, a thickness of 0.3 mm, and a volume of 0.015 cm ³ is formed by applying a solder paste to the surface of the supporting member, and the paste layer is contacted for a test. After contacting the parts,
It is pushed in so that the penetration depth is 0.1 mm (the distance between the interface of the test contact member and the paste layer and the surface of the support member is 0.2 mm), and in this state, the paste layer is formed according to the heating conditions shown below. While heating, the state of the paste layer is photographed by a CCD camera to obtain image data during the fillet formation process. Heating conditions: After heating up to 150 ° C. (preheat temperature t1) at a heating rate of 3 ° C./sec, holding at 150 ° C. for 60 seconds, and then 220 ° C. at a heating rate of 3 ° C./sec (main heating peak After the temperature is raised to the temperature t2), the temperature is maintained at 220 ° C. for 3 seconds. Image processing conditions: Image data was obtained by performing image processing on image data at intervals of 33 msec in continuous image data obtained by a CCD camera to obtain values of shape characteristics of solder paste.

[0055]

[Table 1]

Example 2 and Example 3 A fillet was obtained in the same manner as in Example 1 except that Paste 2 (Example 2) and Paste 3 (Example 3) were used instead of Paste 1, respectively. The average value of the formation time was obtained. The results are shown in Table 2.

[0057]

[Table 2]

Each of the solder pastes evaluated as described above is judged to have good wettability,
That is, it is confirmed that in the case where the fillet formation time is short, a solder paste wettability does not occur, and a highly reliable joint is formed. Therefore, according to the test method of the present invention, It was confirmed that the solder paste can be quantitatively evaluated by the same index.

[0059]

As described above, according to the solder paste testing apparatus of the present invention, the wetness of the solder paste can be determined from the image data of the solder paste which has been heat-treated under the temperature condition to be actually treated. Since it is possible to directly determine the state of, the time when wetting is started in the process of forming the fillet can be specified without causing a large error, and as a result, the wettability of the solder paste can be determined. It is possible to obtain a universal index for quantitatively evaluating the solder paste, which enables reliable and stable evaluation of the wettability of the solder paste regardless of the type of the paste. .

According to the solder paste test method of the present invention, the wet state of the solder paste is directly judged from the image data of the solder paste which has been subjected to the heat treatment under the temperature condition to be actually treated. Therefore, in the process of forming the fillet, the time when wetting is started can be specified without causing a large error, and as a result, the wettability of the solder paste can be quantitatively evaluated. You can get a universal indicator,
Thereby, the wettability of the solder paste can be stably evaluated with high reliability regardless of the type of the paste.

[Brief description of drawings]

FIG. 1 is an explanatory perspective view showing an external appearance of an example of a solder paste characteristic testing device of the present invention.

FIG. 2 is a cross-sectional plan view showing the outline of the configuration of the test apparatus shown in FIG.

FIG. 3 is a vertical cross-sectional view showing the outline of the configuration of the test apparatus shown in FIG.

FIG. 4 is an explanatory diagram showing a configuration example of a light irradiation light unit in the test apparatus shown in FIG.

FIG. 5 is an explanatory diagram showing a state in which light from a light source is applied to an imaging section for which shape characteristics of a solder paste are to be acquired.

FIG. 6 is an explanatory partial cross-sectional view showing an example of a temperature detecting means used to detect the temperature of the solder paste.

FIG. 7 is an explanatory diagram showing an example of a temperature profile for heating the paste layer.

FIG. 8 is an explanatory diagram showing a display example of a test result in a solder paste characteristic test, (a) is a characteristic curve of a solder paste in a fillet forming process, and (b) is an arbitrary time in the fillet forming process. The image data for analysis which shows the state of a solder paste simulated is shown.

FIG. 9 is an explanatory diagram showing the shape characteristics of a solder paste in the process of forming a fillet.

FIG. 10 is an explanatory sectional view showing the outline of the configuration of another example of the solder paste characteristic testing device of the present invention.

FIG. 11 is an explanatory diagram showing a state in which a fillet is formed on the L lead.

FIG. 12 is an explanatory diagram showing a state in which a fillet is formed on a J lead.

FIG. 13 is a diagram showing a solder paste characteristic curve measured by a temperature profile method.

[Explanation of symbols]

10 heater unit 10A front opening 10B side opening 11A, 11B window member 12, 13 Gas supply pipe 14 Gas sampling tube R heating room 20 test piece unit 21 Circuit board (support member) 22A, 22B paste layer 23 Electronic components (test contact members) 24A, 24B electrodes 25 heater table 25A test piece unit mounting surface 26 Sheet heater 30 Upper heating means 31 Lower heating means 35 CCD camera 36 Micro Focus Lens 40 Light irradiation optical system 41 light source 42 first condenser lens 43 Second condenser lens α Rotation angle in horizontal plane β elevation Optical axis of PC CCD camera Optical axis of Q light source L slit light 50,55 Temperature detection means 51 thermocouple 52 holding member 53 Fastener 54 leaf spring θ contact angle h Wet height S wet cross section 60 Stress detection sensor unit 61 Support rod 62 Stress detection sensor 63 holding member 65 Lifting mechanism 66 rotary drive shaft 67 Drive source 70,75 electronic components 71,76 Lead terminal 72 pads 80 Top Fillet 81 heel fillet

Claims (8)

[Claims] 1. A heating chamber is provided, and the paste layer is formed in the heating chamber with the lower end of the test contact member pressed into the paste layer made of the solder paste to be tested from the upper surface of the paste layer. A heater unit for heating, a light irradiation means arranged to illuminate a fillet forming point where the paste layer is heated to form a solder fillet, and a cross section perpendicular to the paste layer forming surface at the fillet forming point. And an image recording means having a field of view facing the solder paste characteristic testing device. 2. The test apparatus according to claim 1, wherein the paste layer is heated according to a preset temperature profile. 3. The light irradiating means projects the optical axis onto a plane including the paste layer forming surface while the optical axis is inclined upward by 0 to 60 ° with respect to the plane including the paste layer forming surface. The test apparatus according to claim 1 or 2, wherein the projection line and the optical axis of the image recording means make an angle of 0 to 170 °. 4. The light irradiating means irradiates the fillet forming portion with slit light, and the width of the slit light is 0.001 to 2 mm. The test apparatus according to any one of 3 above. 5. The temperature detecting means is provided in a state of being pressed into the paste layer at a position outside the visual field of the image recording means, according to any one of claims 1 to 4. Test equipment. 6. An upper wall of the heater unit extends in a vertical direction above an upper wall of a paste layer support member supporting a paste layer of a solder paste to be tested, which is placed in the heating chamber. The stress detection sensor unit having a holding member for holding the test contact member at a predetermined position in the heating chamber, and the test contact member held in the stress detection sensor unit are arranged in the paste layer support member. 6. The test according to claim 1, further comprising an elevating mechanism for moving the entire heater unit relatively upward so that the heater unit is held in a state of entering the paste layer. apparatus. 7. The solder fillet is heated by heating the paste layer in the heating chamber with the lower end of the test contact member pressed into the paste layer made of the solder paste to be tested from the upper surface of the paste layer. In the process of forming a fillet to be formed, in a state where the paste layer is heated to irradiate light to a fillet forming point where a solder fillet is to be formed, image data of a cross section perpendicular to the paste layer forming surface at the fillet forming point. And calculate the shape characteristics of the solder paste by performing image processing on the image data, and when the solder paste begins to melt, or the temperature of the solder paste is substantially the liquidus temperature of the solder paste. Calculated solder paste shape from the time when the same temperature is reached Solder paste characteristic test method of sex and measuring the time required to reach a predetermined stable state. 8. The shape characteristics of the solder paste calculated from the image data are the contact angle (θ) of the solder paste wet to the test contact member, the paste layer forming surface of the paste layer supporting member to the upper edge of the solder paste. The test method according to claim 7, wherein the test method is at least one selected from a wetting height (h) and a solder paste wetting cross-sectional area (S).