KR20040075398A - Miniaturized shear-punch tester and evaluating method of shear strength and shear strain for solder joint - Google Patents

Abstract

PURPOSE: A miniaturized shear-punch tester and a method for evaluating the shear strength and the shear strain for a solder joint are provided to allow a micro-reliability estimation such as sheer strength and sheer strength for a solder joint of electronic parts and to prevent moment from occurring when a sheer change of a conventional single lap shear specimen happens. CONSTITUTION: A miniaturized sheer-punch tester includes a shear-punch tester jig, a load cell(14), a furnace device(5), a reduction gear(15), a linear variable differential transducer, a vacuum device(6), a cooling device, and a control device. An upper die(2) of the shear-punch tester jig and a lower die(3) of the shear-punch tester jig fix a specimen of the solder joint to an upper part of the body. The furnace device(5) surrounds the shear-punch tester jig and heats the surroundings. The load cell(14) is used for measuring a load exerting on the specimen.

Description

MINIATURIZED SHEAR-PUNCH TESTER AND EVALUATING METHOD OF SHEAR STRENGTH AND SHEAR STRAIN FOR SOLDER JOINT}

The present invention relates to a technique of a tester and an evaluation method developed to evaluate microscopically the shear strength and shear strain, which are mechanical properties of solder joints, using a micro shear-punch test piece.

Soldering refers to a method of joining two solids, using a material in a molten state, that is, a solder. The connection between a printed circuit board (PCB) board and a device and the semiconductor and electronic It is a key packaging technology that is very important in the joining process of parts. However, when the electrical and electronic equipment is in operation, the operating temperature range reaches a maximum of 150 ° C. Therefore, due to the difference in the coefficient of thermal expansion (CTE) between the electronic component and the substrate, the solder joint is heated. Shear Stress due to Thermal Stress is generated. As a result, the shear stress component causes disconnection of the solder joint and causes system failure of the entire electronic component. Therefore, the evaluation of shear strength and shear strain on solder joints under shear strain conditions is a very important issue in securing reliability of solder joints.

Currently, the method of evaluating the shear strength of solder joints is a single-lap shear test piece that is made so that the solder joint is 1mm thick and 10mm long by using two Cu plates having a size of about 50 × 10 × 1 ^t mm. Large specimens, such as Lap Shear Specimen) are evaluated. However, such a single lap specimen has a rotational moment in the solder joint during shear deformation, so that the solder deforms other than the shear deformation. Therefore, mechanical properties due to complete shear deformation cannot be obtained. In addition, the size of the test piece is relatively large compared to the size of the micro solder joint of the actual electronic component, which is several tens to hundreds of micrometers in size, and thus the size effect of the test piece is present, so that the shear strength of the fine solder joint is more accurate. Difficulties in evaluation

From the above problems and background, the present invention is a micro shear having a size of 10 × 10 × 0.5 ^t mm including a hole having a diameter of 2.4 mm (or 3.2 mm) filled with a solder alloy that has not been applied until now. -An evaluation method was developed along with the development of a new micro shear-punch tester to evaluate the shear strength and shear strain characteristics of solder joints using a punched specimen (Miniaturized Shear-Punch Specimen). To provide.

The present invention is a very useful test method that makes it possible to evaluate the shear strength and shear strain characteristics of solder joints according to various kinds of solder alloys and bonding conditions with very small micro test pieces. would.

1 is a schematic view of a micro shear-punch tester developed in the present invention,

Figure 2 is a detailed schematic diagram of the fastening site of the shear-punch test piece used in the embodiment of the present invention,

3 is a graph showing the shear stress-shear strain curve behavior of a Sn-37Pb solder joint obtained by a shear-punch test at a temperature junction of 30 ° C.

4 is a graph showing the shear stress-shear strain curve behavior of a Sn-37Pb solder joint obtained by a shear-punch test at a temperature of 50 ° C.

5 is a graph showing the shear stress-shear strain curve behavior of a Sn-4Ag-0.5Cu solder joint obtained by a shear-punch test at a temperature of 30 ° C.

6 is a graph showing the shear stress-shear strain curve behavior of a Sn-4Ag-0.5Cu solder joint obtained by a shear-punch test at a temperature of 50 ° C.

7 is a bar graph showing the maximum shear strength according to the reflow time according to the solder alloy type at a temperature of 30 ℃,

8 is a bar graph showing the maximum shear strength according to the reflow time according to the solder alloy type at a temperature of 50 ℃.

<Description of the code | symbol about the principal part of drawing>

1: solder joint test piece 2: upper die of shear-punch jig

3: bottom die of shear-punch jig 4: stainless steel tube

5: heating furnace 6: vacuum pump

7: Inert gas (Ar) inlet 8: Inert gas (Ar) discharge port

9: cooling water circulation pump 10: cooling water inlet

11: cooling water discharge port 12: motor

13: reduction gear 14: load cell

15: test piece temperature sensor 16: heating furnace temperature sensor

17: micro displacement measuring device 18: control device and data acquisition

Connection line with the system

19: Puncher

In order to achieve the above object, the present invention is first designed and fabricated by the self shearing punch tester. And using a shear-punch tester using a micro test piece having a thin plate thickness (0.5mm) consisting of electronic component material (Cu, Ni) and solder alloy (Solder Joint) in a room temperature ~ 120 ℃ temperature environment (Solder Joint) It provides a method for evaluating the properties of shear strength and shear strain for.

1 is a schematic view of the overall micro-shear-punch tester developed in the present invention, Figure 2 shows a detailed schematic diagram of the fastening portion of the micro-solder joint test piece.

Hereinafter, the configuration of the micro shear-punch tester proposed in the present invention and the process of the shear deformation characteristic evaluation method will be described in more detail.

[Configuration of Microscopic Shear-Punch Tester]

In the micro shear-punch tester for evaluating the shear strength and shear strain characteristics of the solder joint of the electronic component,

① the upper die (2) and the lower die (3) of the shear-punch jig, which is located on the upper part of the main body and fixes the solder joint test piece (1);

(2) a specimen heating furnace (5) surrounding the shear-punch jig (2, 3) and capable of heating the sealable stainless steel tube (4) and the surroundings to a predetermined test temperature;

③ In order to prevent the high temperature oxidation of the test piece (1) and the vacuum pump (6) and inert gas (Ar) injection steel pipe (7) and discharge steel pipe (8) connected into the stainless steel pipe (4) and

④ The cooling water circulation pump 9, the cooling water injection pipe 10, and the discharge pipe 11 connected to the pipe to protect the test device under the heating furnace 5 and

⑤ a motor 12 and a reduction gear for directly applying a load at a constant displacement rate to a test piece 1 positioned at an upper portion of the main body and fixed between the upper die 2 and the lower die 3 of the shear-punch jig; With 13

⑥ Load cell 14 for measuring the load on the test piece

⑦ and the temperature sensor 15 for detecting the temperature of the test piece (1)

⑧ and the temperature sensor 16 for detecting the temperature of the heating furnace (5)

⑨ microdisplacement measuring device (17) connected to the puncher 20 to measure the micro displacement of the test piece (1) and

으로 with a computer-connected connection line 18 to store the above loads and microdisplacements

Micro Shear-Punch Testing Machine

[Configuration of Jig Device for Test Piece Fastening Part of Micro Shear-Punch Tester]

The shear-punch jig

① The lower die (3) having a certain size space to put the test piece (1) and

② the upper die (2) having a predetermined size located on the lower die (3) and

(3) a micro shear-punch tester, characterized in that it consists of a puncher 19 which presses the upper portion of the solder alloy of the test piece through the hole of the upper die 2;

[Method for Evaluating Shear Strength and Shear Strain Characteristics of Solder Joints Using a Micro Shear-Punch Tester]

① On the lower die (3) of the shear-punch jig 2.4 mm (or Place a 10 x 10 x 0.5 ^t mm sized thin specimen (1) filled with solder in a hole of 3.2 mm), place an upper die (2) on it, 2.0 mm (or 2.8mm) puncher 19 and

(2) sealing the shear-punch jig using a stainless steel pipe (4), a plurality of bolts and nuts, and an oil ring;

③ Vacuum the inside of the furnace for 30 minutes with the vacuum pump (6), and then inert gas (Ar) from the inert gas (Ar) container through the injection steel pipe (7) 1.0 Injecting into the

④ the process of raising the temperature of the furnace 5 to a certain test temperature in the temperature range of room temperature to 120 ° C. and maintaining it for about 10 minutes at an error range of ± 1 ° C. at the test temperature before performing the shear-punch test;

⑤ The process of moving the puncher 19 toward the solder joint test piece at a constant displacement speed of 0.2 mm / min using the motor 12 and the reduction gear 13;

⑥ measuring the load P using the load cell 14, and measuring the center displacement δ of the test piece to 1 μm through the microdisplacement measuring device 17;

⑦ shear strain obtained by dividing the measured median displacement δ by the length of the solder joint ( Conversion process

⑧ converting the measured load (P) into shear stress (τ) obtained by dividing the area of the solder joint;

⑨ wherein the shear stress τ is determined by the shear strain ) And the shear stress-shear strain curve

최대 the maximum shear strength (τ _max ) and the maximum shear strain ( _max ), and

공정 a process for checking the behavior of the maximum shear strength (τ _max ) according to the test temperature (T) and

상기 the maximum shear strain according to the test temperature (T) the process of checking the behavior of _max )

공정 confirming the behavior of the maximum shear strength (τ _max ) according to the reflow temperature (T _R );

상기 the maximum shear strain according to the reflow temperature (T _R ) the process of checking the behavior of _max )

공정 a process for checking the behavior of the maximum shear strength (τ _max ) according to the type of solder and

Maximum shear strain according to solder type ( to confirm the behavior of _max )

Micro shear-punch characteristic evaluation method, characterized in that made

Hereinafter, the present invention will be described in more detail with reference to the embodiment using the small punch-creep tester and the test evaluation method.

The material used in this example is Sn-37Pb alloy which is widely used as solder material of electric and electronic parts for comparative evaluation with Pb-free solder alloy.

The melting point (M.P) and solidification temperature range (ΔT) of these alloys are shown in Table 1 below.

Table 1

The solder joint test piece 1 used for the shear-punch test is 10 × 10 × 0.5 ^t mm in size and manufactured under various reflow time conditions of 10sec to 300sec. The shear-punch test temperature of the solder joint is 30 ° C and 50 ° C, and the error range of the furnace 5 is ± 1 ° C. The constant displacement velocity for the load is 0.2mm / min. During the test, the central displacement (δ) of the test piece is precisely measured to a minimum of 1 μm using a microdisplacement measuring device (17). In addition, a shear test is carried out in an argon (Ar) atmosphere using a feeder (7) of an inert gas container to eliminate errors in the test results due to high temperature oxidation of the micro test pieces during the test.

In the present invention, the shear strength and shear strain characteristics of the solder joint are evaluated by a micro shear-punch tester and a micro shear test using a micro test piece. I would like to suggest a method.

< Example 1 >

3 and 4 are shear stress-shear strain curves of copper (Cu) and Sn-37Pb solder joint specimens according to various reflow times obtained using a micro shear-punch tester at 30 ° C and 50 ° C. This figure shows the Shear Stress-Shear Strain Curve.

It can be seen that the overall strain behavior of the shear-punch stress-strain curve is changing with test temperature and reflow time. In particular, it can be observed that the stress-strain curve behavior decreases significantly with increasing test temperature.

< Example 2 >

5 and 6 are shear stress-shear strain curves of copper (Cu) and Sn-4Ag-0.5Cu solder joint specimens obtained using a micro shear-punch tester at 30 ° C and 50 ° C. The figure shows.

In this case, the overall strain behavior of the shear-punch stress-strain curve does not show any significant difference with the reflow time at each test temperature. However, it can be observed that the stress-strain curve behavior with the increase of the test temperature is clearly reduced as in the previous embodiment.

Through the above examples, it can be seen that a clear shear stress-shear-strain curve for the solder alloy joint can be obtained using the micro shear-punch tester and test method developed in the present invention. Can be.

< Example 3 >

7 and 8 are results showing the maximum shear strength (τ _max ) characteristics of the three kinds of solder joint test pieces obtained at 30 ℃ and 50 ℃. First, the maximum shear strength (τ _max ) of the solder joint at 50 ° C was reduced by about 20-30% compared to the 30 ° C of all solder alloys. Sn-4Ag solders in Pb-free solder alloys generally increase the maximum shear strength (τ _max ) as the reflow time increases at 30 ℃ and 50 ℃, while Sn-4Ag-0.5Cu Solder did not show a big difference according to the reflow time. Overall, Pb-free solders showed better bond strength than eutectic Sn-37Pb solders, which may be the result of intermetallic compounds such as Cu ₆ Sn ₅ formed at the joint interface. The micro shear-punch test results show that the three alloy species Sn-4Ag-0.5Cu solder joints exhibit the best shear strength properties.

Micro shear using the micro solder joint test piece from the results of the above test results, that is, the shear stress-shear strain curve behavior and the maximum shear strength (τ _max ). -The shear-punch tester and evaluation method can be applied as a new tester and evaluation method for evaluating the shear strength characteristics at the interface of the junction according to the solder alloy type and the soldering conditions.

As described above, the present invention, that is, the micro shear-punch tester and the evaluation method using the micro test piece, according to various electronic component base materials and solder alloys and soldering conditions, shear strength and shear on the solder joint of the electronic component Enable micromechanical reliability assessments such as shear strain. In addition, it is possible to completely solve the effects such as the generation of moment during shear deformation of the conventional single lap shear specimen (Single Lap Shear Specimen).

Claims (3)

In the micro shear-punch tester for evaluating the shear strength and shear strain characteristics of the solder joint of the electronic component, ① the upper die (2) and the lower die (3) of the shear-punch jig, which is located on the upper part of the main body and fixes the solder joint test piece (1); (2) a specimen heating furnace (5) surrounding the shear-punch jig (2, 3) and capable of heating the sealable stainless steel tube (4) and the surroundings to a predetermined test temperature; ③ In order to prevent the high temperature oxidation of the test piece (1) and the vacuum pump (6) and inert gas (Ar) injection steel pipe (7) and discharge steel pipe (8) connected into the stainless steel pipe (4) and ④ The cooling water circulation pump 9, the cooling water injection pipe 10, and the discharge pipe 11 connected to the pipe to protect the test device under the heating furnace 5 and ⑤ a motor 12 and a reduction gear for directly applying a load at a constant displacement rate to a test piece 1 positioned at an upper portion of the main body and fixed between the upper die 2 and the lower die 3 of the shear-punch jig; With 13 ⑥ Load cell 14 for measuring the load on the test piece ⑦ and the temperature sensor 15 for detecting the temperature of the test piece (1) ⑧ and the temperature sensor 16 for detecting the temperature of the heating furnace (5) ⑨ microdisplacement measuring device (17) connected with the puncher 20 to measure the micro displacement of the test piece (1) and 으로 with a computer-connected connection line 18 to store the above loads and microdisplacements Micro shear-punch tester, characterized in that The shear-punch jig ① The lower die (3) having a certain size space to put the test piece (1) and ② the upper die (2) having a predetermined size located on the lower die (3) and (3) through a hole in the upper die (2) to a puncher (19) for pressing the upper portion of the solder alloy of the test piece Micro shear-punch tester, characterized in that ① On the lower die (3) of the shear-punch jig 2.4 mm (or 3.2 mm), a thin plate-shaped specimen (1) having a size of 10 × 10 × 0.5 ^t mm filled with solder is placed thereon, and an upper die (2) is placed thereon and the hole of the upper die 2.0 mm (or 2.8mm) puncher 19 and (2) sealing the shear-punch jig using a stainless steel pipe (4), a plurality of bolts and nuts, and an oil ring; ③ Vacuum the inside of the furnace for 30 minutes with the vacuum pump (6), and then inert gas (Ar) from the inert gas (Ar) container through the injection steel pipe (7) 1.0 Injecting into the ④ the process of raising the temperature of the furnace 5 to a certain test temperature in the temperature range of room temperature to 120 ° C. and maintaining it for about 10 minutes at an error range of ± 1 ° C. at the test temperature before performing the shear-punch test; ⑤ The puncher 19 is moved toward the solder joint test piece at a constant displacement speed of 0.2 mm / min using the motor 12 and the reduction gear 13; ⑥ measuring the load P using the load cell 14, and measuring the center displacement δ of the test piece to 1 μm through the microdisplacement measuring device 17; ⑦ shear strain obtained by dividing the measured median displacement δ by the length of the solder joint ( Conversion process ⑧ converting the measured load (P) into shear stress (τ) obtained in the area of the solder joint; ⑧ the shear stress τ equals the shear strain ) And the shear stress-shear strain curve 최대 the maximum shear strength (τ _max ) and the maximum shear strain ( _max ), and 공정 a process for checking the behavior of the maximum shear strength (τ _max ) according to the test temperature (T) and 상기 the maximum shear strain according to the test temperature (T) the process of checking the behavior of _max ) 공정 confirming the behavior of the maximum shear strength (τ _max ) according to the reflow temperature (T _R ); 상기 the maximum shear strain according to the reflow temperature (T _R ) the process of checking the behavior of _max ) 공정 a process for checking the behavior of the maximum shear strength (τ _max ) according to the type of solder and Maximum shear strain according to solder type ( to confirm the behavior of _max ) Micro shear-punch characteristic evaluation method, characterized in that made