0

10

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40

Solder Heat Shift (%)

C004

0

50

100

150

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300

0

50

100

150

200

250

300

350

400

Time (seconds)

C01

14

REF6225, REF6230, REF6233, REF6241, REF6245, REF6250

SBOS748 – SEPTEMBER 2016

www.ti.com

Product Folder Links: REF6225 REF6230 REF6233 REF6241 REF6245 REF6250

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Copyright © 2016, Texas Instruments Incorporated

7 Parameter Measurement Information

7.1 Solder Heat Shift

The materials used in the manufacture of the REF62xx have differing coefficients of thermal expansion, and

result in stress on the device die when the part is heated. Mechanical and thermal stress on the device die

sometimes causes the output voltages to shift, degrading the initial accuracy specifications of the product. Reflow

soldering is a common cause of this error.

In order to illustrate this effect, a total of 128 devices were soldered on eight printed circuit boards (PCBs), with

16 devices on each PCB, using lead-free solder paste, and the manufacturer-suggested reflow profile. The reflow

profile is as shown in Figure 39. The printed circuit board is comprised of FR4 material. The board thickness is

1.65 mm and the area is 101.6 mm × 127 mm.

The reference output voltage is measured before and after the reflow process; the typical shift is displayed in

Figure 40. Although all tested units exhibit very low shifts (< 0.03%), higher shifts are also possible depending on

the size, thickness, and material of the PCB.

The histogram displays the typical shift for exposure to a single reflow profile. Exposure to multiple reflows, as is

common on PCBs with surface-mount components on both sides, causes additional shifts in the output bias

voltage. If the PCB is exposed to multiple reflows, solder the device in the final pass to minimize exposure to

thermal stress.

Figure 39. Reflow Profile

Figure 40. Solder Heat Shift Distribution