7 Parameter Measurement Information

7.1 Solder Heat Shift

The materials used in the manufacture of the REF60xx 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 7-1. The printed circuit board is comprised of FR4 material. The board

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

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

Figure 7-2. 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.

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Time (seconds)

C01

Figure 7-1. Reflow Profile

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Solder Heat Shift (%)

C004

Figure 7-2. Solder Heat Shift Distribution

REF60

SBOS708C – MAY 2016 – REVISED APRIL 2026

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