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C01

REF5010, REF5020, REF5025, REF5030

REF5040, REF5045, REF5050

SBOS410G – JUNE 2007 – REVISED NOVEMBER 2015

www.ti.com

8 Parameter Measurement Information

8.1 Solder Heat Shift

The materials used in the manufacture of the REF50xx have differing coefficients of thermal expansion, resulting

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

output voltages to shift, degrading the initial accuracy and drift specifications of the product. Reflow soldering is a

common cause of this error.

To illustrate this effect, a total of 36 devices were soldered on printed-circuit-boards using lead-free solder paste

and the paste manufacturer suggested reflow profile. The reflow profile is as shown in Figure 28. The printed-

circuit-board is comprised of FR4 material. The board thickness is 0.8 mm and the area is 13 mm × 13 mm.

The reference voltage is measured before and after the reflow process across temperature; the typical shift of

accuracy and drift is displayed in Figure 29 through Figure 36. Although all tested units exhibit very low shifts,

higher shifts are also possible depending on the size, thickness, and material of the printed-circuit-board. An

important note is that the histograms display 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, the device should be soldered in the last

pass to minimize its exposure to thermal stress.

Figure 28. Reflow Profile

12

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