REF50 datasheet(20/52 Pages) TI2

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7 Parameter Measurement Information

7.1 Solder Heat Shift

The materials used in manufacturing 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, 36 devices are soldered on printed-circuit-boards using lead-free solder paste and the

paste manufacturer suggested reflow profile. Figure 7-1 shows the reflow profile. The printed-circuit-board is

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

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

accuracy and drift is displayed in Figure 7-2 for REF50xxEI and Figure 7-3 through Figure 7-10 for REF50xx.

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 printed circuit boards (PCBs)

with surface-mount components on both sides, causes additional shifts in the output bias voltage. If the PCB

is exposed to multiple reflows, then solder the device in the last pass to minimize device exposure to thermal

stress.

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Time (seconds)

C01

Figure 7-1. Reflow Profile

Figure 7-2. Solder Heat Shift Distribution (%), REF50xxEI

REF50, REF50E

SBOS410O – JUNE 2007 – REVISED OCTOBER 2025

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