GB/T 31475-2015Requirements for solder paste for high-quality interconnections in electronics assembly (English PDF)

3.1 Slump

When the solder paste coating test is performed, the shape of the solder paste pattern printed on the substrate changes, which is a type of solder paste.

defect.

3.2 Tackiness

The amount of solder paste adhesion to components and the change in solder paste adhesion after printing time increases.

3.3 Wetting

The molten solder spreads on the surface of the base metal and forms a smooth solder layer, and the angle between the molten solder and the base metal is less than 90 °.

3.4 Thinner

Liquid preparations or pastes with or without activator, added to the solder paste to adjust the viscosity and solids of the solder paste content.

4.1 Classification

Solder paste can be divided into leaded solder paste and lead-free solder paste according to alloy composition. For the classification of flux in solder paste, see GB/T 31474.

Flux for electronic assembly high quality internal interconnection.

4.2 Named tags

The naming mark of the solder paste should meet the following requirements.

Example. If the solder alloy grade of a solder paste is S-Sn5PbAgA, the flux type is identified as ROM1, and the mass fraction of the alloy powder in the solder paste is

85%, alloy powder type is type 1, viscosity is 800Pa · s, then it is expressed as follows. Sn5PbAgA-ROM1-85-1-800Pa · s.

5.1 Chemical composition

The chemical composition of the solder powder in the solder paste should meet the requirements of GB/T 31475.

5.2 Impurity content

The impurity content of solder powder in solder paste should meet the requirements of GB/T 31475.

5.3 Size distribution

The size distribution and specification type of solder powder in solder paste shall comply with the requirements in Table 1.

Table 1 Summary of solder powder size distribution and specifications

5.4 Shape

The shape of the solder powder should be spherical, and the maximum ratio of long axis to short axis of type 1, 2 and 3 solder powder and type 4, 5 and 6 solder powder is 1.5 respectively.

The mass of the spherical powder and the spherical powder of 1.2 should be no less than 90%.

5.5 Alloy powder content

The mass fraction of the alloy powder in the solder paste should be in the range of 65% ~ 96%.

5.6 Viscosity

Solder paste viscosity should be within ± 15% of the nominal value of the product.

5.7 Collapse

5.7.1 0.20mm template test

Use a 0.20mm stencil to print a 0.63mm × 2.03mm graphic. When the test method 6.5.2.2a) is used, the spacing is not less

0.56mm, there should be no bridging between the solder paste patterns; when the test method 6.5.2.2b) is used, the pitch is not less than 0.63mm, the solder

There should be no bridging between the paste patterns.

Use a 0.20mm stencil to print a 0.33mm × 2.03mm graphic. When the test method 6.5.2.2a) is used, the pitch is not less than

0.25mm, there should be no bridging between the solder paste patterns; when the test method 6.5.2.2b) is used, the pitch is not less than 0.30mm, the solder

There should be no bridging between the paste patterns.

Use a 0.10mm stencil to print 0.33mm × 2.03mm graphics. When the test method 6.5.2.2a) is used, the pitch is not less than

0.25mm, there should be no bridging between the solder paste patterns; when the test method 6.5.2.2b) is used, the pitch is not less than 0.30mm, the solder

There should be no bridging between the paste patterns.

Print a 0.20mm × 2.03mm graphic with a 0.10mm stencil. When the test method 6.5.2.2a) is used, the pitch is not less than

0.175mm, there should be no bridging between the solder paste patterns; when the test method 6.5.2.2b) is used, the pitch is not less than 0.20mm, the solder

There should be no bridging between the paste patterns.

5.8 Tin Bead Test

The solder paste bead test is rated according to the provisions of Table 2, and the test results cannot be lower than level 2.

Table 2 Tin ball test evaluation standards

Grade test results

1 After each solder paste spot is melted, a single solder ball is formed, and no more than 1 independent solder ball appears next to any solder ball

2 After each solder paste spot is melted, a single solder ball is formed, and the number of independent solder beads appearing beside any solder ball is not more than 3.

After each solder paste spot is melted, a single solder ball is formed, and the number of independent solder beads appearing beside any solder ball is more than three, but these

Tin beads have not formed a semi-continuous ring arrangement

After each solder paste spot is melted, a single solder ball is formed, and there are a large number of solder beads next to any solder ball, and a semi-continuous ring row is formed.

Column; or after the solder paste melts, a diameter greater than 75 µm (or greater than 50 µm) is formed next to the solder ball.

Solder paste)

Note. For solder paste made with type 1, 2, 3 or 4 type alloy powder, the diameter of each solder ball should not be greater than 75 µm; for type 5 or 6

For solder paste made of alloy powder, the diameter of each solder ball should not be greater than 50 µm.

5.9 Adhesiveness

When tested in accordance with 6.8, the minimum adhesion of solder paste after printing should be within ± 30% of the nominal value of the product.

5.10 Wettability

When tested in accordance with 6.9, the wettability of the solder paste should meet the level 1 or 2 evaluation criteria in Table 3.

Table 3 Solder Paste Wettability Evaluation Standards

Grade test results

1 The molten solder in the solder paste wets the specimen and spreads beyond the boundaries of the area to which the solder paste is applied

2 The area where the solder paste is applied on the sample is completely wetted by the molten solder in the solder paste

3 Part of the sample (area ratio is not greater than 15%) The area where the solder paste is applied is not wet by the molten solder in the solder paste

It is obvious (area ratio greater than 15%) on the sample that the area where the solder paste is applied is not wet by the molten solder in the solder paste, or the molten solder in the solder paste

Material to form two or more solder wetted surfaces

5.11 Flux Performance

The properties and types of flux in solder paste should meet the requirements of GB/T 31474.

6.1 Chemical composition

The chemical composition of solder paste alloy powder is measured according to GB/T 10574 or YS/T 746.

6.2 Test method for size distribution of alloy powder

6.2.1 Instruments and materials

The required equipment and materials are as follows.

a) thinner;

b) stirring rods;

c) 50mL measuring cup;

d) Microscope. 100 times magnification;

e) Measuring eyepiece. scale 10µm;

f) microscope slides;

g) Balance. accuracy ± 0.01g.

6.2.2 Test procedure

Stir the solder paste at room temperature, weigh 1g, put it into a clean measuring cup and add 4g thinner, stir and dilute

Flux and solder paste to make it a homogeneous mixture. Place a small drop of the mixture on a clean microscope slide and cover it with a clean glass

Sheet, press gently to spread it between the two glass sheets. Observe the size of about 50 alloy powder particles in the field of view with a microscope.

Measure their long axis and short axis, calculate their mass one by one, calculate the total amount and its mass fraction according to the size distribution file, and record according to Table 4.

Table 4 Test record of size distribution of alloy powder

Note. The shape of the alloy powder particles is judged based on the measurement of the major and minor axes and recorded according to 5.4.

6.3 Alloy powder content

6.3.1 Instruments and materials

The required equipment and materials are as follows.

a) Balance. accuracy ± 0.01g;

b) crucible;

c) heating plate;

d) Glycerol. analytical grade;

e) Anhydrous ethanol. analytical grade.

6.3.2 Inspection steps

Stir the solder paste at room temperature, weigh 10g ~ 15g into a clean crucible and add 30mL glycerol.

The crucible is heated for 15min under the condition that the liquidus temperature (or eutectic point) of the alloy powder exceeds the temperature of 25 ° C to 30 ° C, so that the alloy powder is fully melted and cooled.

When it reaches room temperature, the alloy is allowed to solidify. The solidified alloy block is taken out, and its surface is cleaned with anhydrous ethanol. After drying, the mass is weighed with a balance.

6.3.3 Calculation

Calculate the mass fraction of alloy powder in solder paste according to formula (1).

6.4 Viscosity

6.4.1 Instruments and materials

The required equipment and materials are as follows.

a) Brookfield T-pin rotor or helical-pin rotor viscometer;

b) Malcom screw pump viscometer.

You can choose any of the above viscometers or other equivalent rheometers for testing.

6.4.2 Test samples

Before the test, the solder paste samples should be left to stand in an environment of 25 °C ± 1 °C for a period of not less than 24h.

When testing with a Brookfield T-pin rotor viscometer, the sample volume should be sufficient to fill the test container (the diameter and height of the test container (Degrees are not less than 5cm); when using Brookfield spiral needle rotor or Malcom screw pump viscometer for testing, the sample size is about

Inspection container volume 60%.

6.4.3 Test procedure

6.4.3.1 Sample preparation

Prepare the specimen according to the following procedure.

a) Open the container containing the solder paste sample, remove the inner cover, and scrape the sample adhered to the outer cover, inner cover and container wall back into the container;

b) Using a spatula, stir the sample evenly (1min ~ 2min), taking care to prevent air from mixing into the sample;

c) Transfer an appropriate amount of sample into the test container, taking care to prevent the introduction of air (if the size of the container

Required, this step is not required);

d) The test container is allowed to stand in a constant temperature environment of 25 °C ± 0.25 °C until the temperature and rheological properties of the sample reach a stable state.

The interval should be not less than 15min, depending on the nature of the solder paste sample, the standing time can be appropriately extended.

6.4.3.2 Test

6.4.3.2.1 Brookfield T-pin Rotor Viscometer

Set the rotation speed to 5r/min and select a suitable T-pin rotor (the selection of the rotor to ensure that the torque percentage reading is between 10% and 100%

Within range. If the viscosity is below 300kcp, select TC type rotor; when the viscosity is 300kcp ~ 1600kcp, select TF type (Rotor); adjust the movable range of the lifting bracket so that the T-pin rotor can be immersed in the sample to a depth of 0.3cm ~ 2.8cm

Up and down movement between fields (minimum distance between the rotor and the bottom of the test container is not less than 1cm); set a test period of 5 cycles (lift and lower

The up and down movement of the bracket is one cycle at a time); start the test, and continuously record the viscosity of the rotor during the up and down reciprocating movement of the rotor with the lifting bracket

Changes in value. During the test, the sample temperature should be kept at 25 °C ± 0.25 °C.

6.4.3.2.2 Brookfield Spiral Needle Rotor or Malcom Spiral Pump Viscometer

Dip the instrument sensor into the solder paste sample, pay attention to prevent the sample from covering the screw pump outlet; set the speed to 10r/min; start measuring

Try to record the data when the reading is stable for more than 1min and no longer changes. During the test, the sample temperature should be kept at 25 °C ± 0.25 °C.

6.4.4 Evaluation of results

6.4.4.1 Brookfield T-pin Rotor Viscometer

Take the maximum and minimum viscosity values measured in the first two cycles and record them as eta1 and eta2 respectively; take the maximum and minimum viscosity measured in the last two cycles

The values are recorded as eta3 and eta4, respectively. Calculate the viscosity values eta and eta 'of the solder paste samples according to equations (2) and (3).

eta = (eta1 eta2)/2 (2)

eta '= (eta3 eta4)/2 (3)

If eta <= (1 10%) eta ', the final viscosity of the sample is recorded as eta'; if eta > (1 10%) eta ', the result is considered invalid, and the sample is allowed to stand still and stable

After the test is repeated, the result is judged in the above manner.

6.4.4.2 Brookfield Spiral Needle Rotor or Malcom Spiral Pump Viscometer

Record the stable data, which is the viscosity value of the solder paste sample.

6.5 Collapse test

6.5.1 Instruments and materials

The required equipment and materials are as follows.

a) stencil (missing printing plate). according to the regulations of Figure 1 and Figure 2 respectively;

b) Sample carrier. Frosted glass sheet with a size of 76mm × 25mm and a thickness of at least 1mm is used as the standard sample carrier.

Equivalent to alumina substrate or epoxy glass fiber cloth substrate; the number of sample carriers is 4;

c) scraper;

d) temperature controlled heating furnace;

e) 10x magnifying glass.

6.5.2 Test procedure

6.5.2.1 Sample preparation

Prepare the specimen according to the following procedure.

a) Use two stencils with different thicknesses (different opening sizes) (see Figure 1 and Figure 2) to print solder paste patterns on two carriers to form

For 4 samples, the printed solder paste pattern should be uniform, and there should be no residual solder paste outside the pattern;

b) Two samples printed from each stencil are coded as 1

The required equipment and materials are as follows.

a) Metal stencil. For metal paste used for solder paste of type 1, 2, 3 and 4 alloy powder, its size is 76mm × 25mm

× 0.2mm, there must be at least three circular leak holes with a diameter of 6.5mm and a center distance of 10mm on the metal template. Du Cai

Metal stencils for solder pastes with type 5 and 6 alloy powders.The dimensions are 76mm × 25mm × 0.1mm.

There must be at least 3 circular leak holes with a diameter of 1.5mm and a center distance of 10mm on the board;

b) Sample carrier. The sample carrier is an alumina substrate, with a thickness of 0.60mm to 1.00mm, and a minimum length and width of 75mm and

25mm. Other non-wetting substrates can also be used;

c) heating plate;

d) surface thermometer;

e) Magnifying glass. 10 times to 20 times;

f) Microscope. 100x ~ 150x;

g) Measuring eyepiece. scale 10µm;

h) scraper;

i) solvents;

j) Deionized water.

6.6.2 Test procedure

After the solder paste at room temperature is stirred evenly, it is printed on the sample carrier with a prescribed metal template to form a sample.

kind. The solder paste should fill each leak of the metal template and scrape it. Place the sample at a temperature of 25 ° C ± 2 ° C and a relative humidity of 50% ±

10% environment for standby; the first and second samples are 15min ± 5min and 240min ± 15min after solder paste printing, respectively

It is placed on a heating plate for heating.The temperature of the heating plate should be controlled above the liquidus (or eutectic point) temperature of the alloy powder in the solder paste.

In the range of 25 °C ~ 30 °C, after the alloy powder in the solder paste is melted and shaped, the sample is taken out from the hot plate in a horizontal manner, and the alloy powder is

After melting and setting, the contact time of the sample on the hot plate should not exceed 10s.

6.6.3 Evaluation of results

After the sample is cooled to room temperature, check whether the sample has tin beads with a magnifying glass; observe the tin beads next to the solder ball with a microscope and measure

Tin bead size; compare the test results with the evaluation criteria in Table 2 to determine the grade of the tin bead test results.Figure 3 shows the results of the tin bead test results.

Typical photo.

a) preferred b) acceptable c) difficult to accept d) unacceptable

Figure 3 Results of the tin bead test

6.7 Adhesion test

6.7.1 Instruments and materials

6.7.1.1

Other equipment that can accurately determine adhesion at the specified speed during the test. The test equipment shall have a diameter of 5.10mm

± 0.13mm stainless steel probe with smooth and flat bottom surface, and can be adjusted to be parallel to the surface of the test sample. The probe can be controlled at a

A controlled contact force is used to contact the sample, and the probe is withdrawn at a controlled speed from the surface of the test sample.

Maximum force

6.7.1.2 Sample carrier

The sample carrier is a copper-clad epoxy fiberglass cloth substrate (that is, a PCB substrate), and other equivalent substrates can also be used.

The minimum length and width are 75mm and 25mm.

6.7.2 Test procedure

Print at least 3 solder paste patterns with a diameter of not less than 6.5mm on the sample carrier, and the solder paste pattern spacing should not be less than 10mm.

And mark it in an appropriate way to distinguish the sample storage time after printing solder paste. Prepared samples should be stored at temperature before measurement

It is 25 °C ± 2 °C and the relative humidity is 50% ± 10%. Place the specimen horizontally under the test probe, and align the probe with the 3 welds.

One of the solder paste patterns, and then make the test probe contact the solder at a speed of 2.5mm/min ± 0.5mm/min and a force of 3.0N ± 0.3N.

Withdraw the probe pattern from the solder paste pattern at a speed of 2.5mm/min ± 0.5mm/min within 5s after this force is applied, and record

Test the maximum force with which the probe is released from the solder paste pattern. Under the same test conditions, measure at least 5 more times, and take the average value as the adhesion

Force results, and record the time after the solder paste pattern is printed on the test sample.

6.7.3 Evaluation of results

The evaluation of the initial adhesion of the solder paste should be performed immediately after the solder paste is printed.

The value that changes with the increase of the setting time, the solder paste adhesion test results are given in the following way.

a) initial adhesion value;

b) the time (h) when the initial adhesion value drops to 80% of its value c) the minimum adhesion within the specified holding time.

6.8 Wettability test

6.8.1 Instruments and materials

The required equipment and materials are as follows.

a) heating plate;

b) specimen clamp;

c) 400mL beaker;

d) 10x magnifying glass;

e) 5% mass sulfuric acid solution;

f) deionized water;

g) Isopropanol. analytical grade;

h) flux cleaning agents;

i) Stencil. The thickness of the stencil is 0.2mm, there are at least 3 circular holes with a diameter of 6.5mm on the stencil, and the minimum center distance of the holes is

10mm.

6.8.2 Test procedure

An oxygen-free copper sheet conforming to GB/T 2040 with a thickness of 0.8mm was prepared into a rectangular specimen of 76mm × 25mm with 5% sulfur

Wash with acid solution for 15 ~ 20min, wash with water, rinse with isopropanol, dry at room temperature, put in deionized water for 10min, and dry in air

30min; print the solder paste on the sample with the selected stencil, heat the sample according to 6.6.2 and cool to room temperature, then remove with a cleaning agent

Flux remains on its surface.

6.8.3 Evaluation of results

Visual inspection with a 10x magnifying glass, and determine the solder wetting grade according to the evaluation criteria in Table 3.

6.9 Flux performance test

The test method for the performance of the flux in solder paste is carried out in accordance with GB/T 31474.

7.1 Inspection classification

Inspections are divided into settlement tests (see 7.3) and routine tests (see 7.4).

7.2 Inspection lot

The inspection lot shall consist of products of the same grade, type and specification submitted at the same time.

7.3 Settlement test

7.3.1 Sampling plan

Sampling shall be carried out according to the special inspection level S-1 of GB/T 2828.1 and a normal sampling plan.

7.3.2 Test items

Inspection items, sequence and acceptance quality limits shall be carried out in accordance with the provisions of Table 7.

Table 7 Settlement test

Test project requirements chapter number method chapter number acceptance quality limit (AQL)

Alloy powder content 5.5 6.3 1.5

Viscosity 5.6 6.4 4.0

Collapse 5.7 6.5 2.5

Wettability 5.10 6.8 1.5

7.3.3 Eligibility criteria

There is one failure in the delivery test, and double the number of samples from the batch of products should be taken for the re-inspection of the unqualified item.

If it fails, the entire batch fails.

7.4 Routine tests

7.4.1 Test items

The routine test cycle for solder paste is one year. The test items shall be carried out in accordance with the provisions of Table 8. The test sequence should not affect the subsequent test results.

The principle of fruit is tested.

Table 8 Routine tests

7.4.2 Sample size

Routine test samples should be randomly selected from the smallest batch of solder paste products from the batch that passed the delivery test inspection.

7.4.3 Non-conformance determination

If one test fails, the routine test is unsuccessful.

7.4.4 Disqualification

If the routine test is unsuccessful, the product shall stop delivery testing and production, and the supply and demand parties shall resolve the products delivered within this cycle through consultation.

Manufacturers should find out the reasons, and immediately take measures in production until the routine test is qualified before they can resume the product delivery test.

8.1

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