ED-7306_E - 第8页

JEITA ED-7306 - 6 - 5.2.2 The temperatures for measurements are - room temperature, - melting point, - peak tempe rature, - solidification point, and - room temperature after cool down. The melting point and the solidifi…

JEITA ED-7306

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4. Sample

4.1 Sample size

At least three samples are required for each measurement condition.

4.2 Solder ball removal

If the measurement method of the package warpage requires the elimination of the solder balls from a

package, it is recommended to use mechanical removal rather than hot reflow. If the samples are prepared

without solder balls for the convenience of the measurement, the package shall be subjected to the thermal

history of the solder ball attachment process.

4.3 Pretreatment conditions

The bake and moisture soak conditions shall conform to the moisture sensitivity level specified in TEST

METHOD 301B, JEITA ED-4701/300. The peak temperature of the package warpage measurement shall

meet the specification of the product.

4.4 Maximum time after pretreatment until measurement

It is recommended to measure the warpage no longer than 5 hours after the pretreatment.

4.5 Repetition of the reflow cycles for the sample

The same sample shall not be subjected to the repetition of the reflow cycles. The sample can be subjected

to more than one cycle of reflow for remeasurement, only if reproducibility of test data was verified prior to

the test.

5. Measurement

5.1 General description

The package warpage is measured by “shadow moiré method” or “laser reflection method”.

Samples are subjected to heating and cooling while measuring the package warpage at the temperatures

specified in 5.2. The measurement points shall not be on the crown of solder balls but on the substrate

surface of the package. Only when the behavior of the top surface of the package (mostly marking surface)

is verified to coincide with that of the substrate surface, the measurement on the top surface is allowed.

5.2 Temperature profile and the temperatures for measurements

5.2.1 The temperature profile for the warpage measurement does not necessarily simulate that for

production. Higher priorities are placed on

- maintaining the temperature constant during the measurement,

- never exposing the samples more than necessary duration at high temperature. Samples shall be

proceeded to the next measurement as soon as possible,

- avoiding a temperature surge to prevent the overshoot, and

- minimizing the temperature difference between the top and bottom surfaces.

JEITA ED-7306

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5.2.2 The temperatures for measurements are

- room temperature,

- melting point,

- peak temperature,

- solidification point, and

- room temperature after cool down.

The melting point and the solidification point are 220°C for Sn-3.0Ag-0.5Cu solder as a reference. Other

solder composites may take different temperatures. The peak temperature basically conforms to the

package classifications specified in TEST METHOD 301B, JEITA ED-4701/300, but to be exact, it shall

follow the supplier’s recommended max temperature.

5.2.3 It is recommended that a thermocouple of gauge 30 (φ0.25 mm) or flat tip type be used.

5.2.4 The thermocouple is attached on the center of the package body using either thermally conductive

epoxy or heat-resistant polyimide tape. When polyimide tape is used, thermally conductive sheet shall

be applied between the thermocouple bead and the package surface to enhance thermal conductivity

as a thermal interface material.

5.2.5 When a measuring instrument is being set up, the temperature of the molded side of the package

facing a heater is also measured. The temperature difference from the substrate surface shall

preferably be less than 10°C by adjusting the heating mechanism and the temperature profile.

Fig. 6 Thermocouple placement

5.3 Measurement method

5.3.1 Shadow moiré method

Solder balls shall be removed prior to the measurement on the substrate surface. Measurements are

conducted by placing the grating (low CTE glass with transparent and opaque stripes) parallel to the

sample. Then, the projection of light beam at an angle of approximately 45° through the grating produces

the stripe pattern on the sample. Observation of the stripe pattern through the grating results in the moiré

fringe pattern (geometric interference pattern). Image processing and the analysis of the patterns provide

the displacement from planarity over the substrate surface. The instrument is capable of setting the

measuring zone and measuring the warpage at elevated temperatures including the peak temperature.

Heater side

Package

Thermocouple on the substrate

side for temperature profile

control (warpage measurement

side)

Thermocouple on the molded

side for one time adjustment of

the temperature difference

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5.3.2 Laser reflection method

Solder balls shall be removed when the solder ball pitch is not large enough for laser beam to measure the

warpage on the substrate surface. Samples are placed on the measurement table. The displacement from

the flatness is measured by the laser displacement sensor. The warpage is generally measured by

scanning the laser beam over the terminal lands or between balls throughout the measuring zone. The grid

pitch of the measurement points is preferably less than the solder ball pitch. The instrument is capable of

setting the measuring zone and measuring the warpage at elevated temperatures including the peak

temperature.

5.3.3 Data analysis (Data table, Diagonal scan graph, 3D plot graph)

The magnitude of the warpage is obtained from the data table of the measurements or 3D plot graph

(warpage distribution diagram over the measuring zone). Then the sign of the warpage (warpage direction)

is determined from the diagonal scan graph and precedes the value.

6. Maximum permissible package warpage at elevated temperature

The criteria of the maximum permissible package warpages for BGA and FBGA are specified in Table 1,

and those for FLGA are specified in Table 2.

Table 1 Maximum permissible package warpages for BGA and FBGA

Unit: mm

Solder ball pitch 0.4 0.5 0.65 0.8 1.0 1.27

Condition of ball height 0.20 0.25 0.33 0.35 0.40 0.50 0.60

Maximum permissible package warpage

(Absolute value)

0.10 0.11 0.14 0.17 0.17 0.22 0.25

Table 2 Maximum permissible package warpages for FLGA

Unit: mm

Land pitch 0.4 0.5 0.65 0.8

Condition of thickness of molten solder

paste

0.08 0.10 0.11 0.13

Maximum permissible package warpage

(Absolute value)

0.08 0.10 0.11 0.13