CMA3000 Datasheet, PDF (10/18 Pages) VTI technologies – 3-axis accelerometer

CMA3000 Assembly Instructions
VTI Technologies’ acceleration sensors can be soldered on commonly used substrates, e.g. FR-4,
ceramic, flex-print etc. The pad metallization should be solder wettable in order to assure good
quality solder joints. Generally used circuit board finishes for fine pitch SMD soldering are NiAu,
OSP, I-Sn, and I-Ag.
5.2 Solder Paste
For the optimum metallurgical compatibility, it is recommended to solder the CMA3000 component
with lead-free SAC-based (tin-silver-copper) solder paste as the solder spheres on the CMA3000
component are based on this alloy. A near eutectic solder paste composition is recommended. The
melting point of lead-free SAC solder can vary between 217–221°C, depending on the composition
of the solder alloy. A no-clean solder paste is recommended as ultrasonic agitation wash of the
CMA3000 component is prohibited. The solder paste must be suitable for printing it through the
stencil aperture dimensions. Type 3 paste is recommended (grain size 25-45µm).
5.3 Stencil
The solder paste is applied onto the PWB by using stencil printing. The stencil thickness and
aperture determines the precise volume of solder paste deposited onto the land pattern. Stencil
alignment accuracy and consistent solder volume transfer are important parameters for achieving
uniform reflow soldering results. Too much solder paste can cause bridging and too little solder
paste can cause insufficient wetting. Generally the stencil thickness needs to be matched to the
needs of all components on the PWB. The recommended stencil openings and dimensions for the
CMA3000 component are presented in Figure 9.
Stencil opening
Stencil thickness
Round 300 µm
(+0, -25 µm)
Square 275 µm x 275 µm
(±0 µm)
100 µm
(±25 µm)
100 µm
(±25 µm)
Figure 9. Recommended stencil openings and dimensions for CMA3000 component. Round
openings are preferred.
VTI Technologies Oy
www.vti.fi
PRELIMINARY
Subject to changes
TN68
10/18
Rev.09