7 Parameter Measurement Information

7.1 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 7-1. 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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C01

Figure 7-1. Reflow Profile

REF5010, REF5020, REF5025, REF5030, REF5040, REF5045, REF5050

SBOS410M – JUNE 2007 – REVISED DECEMBER 2024

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