SCA3000 Assembly Instructions

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.

For the SCA3000 MID-package the recommended stencil thickness is 5mils (127µm).

Stencil apertures in general should be 1:1 to PWB pad sizes, or stencil apertures could even be

reduced by 1mil (25.4µm) from all sides in regard to the PWB land pad size. This reduction of

aperture size can reduce bridging between solder joints.

5.4

Paste Printing

The paste printing speed should be adjusted according to the solder paste specifications. It is

recommended that care be taken during paste printing in order to ensure correct paste amount,

shape, position, and other printing characteristics. Neglecting any of these can cause open solder

joints, bridging, solder balling, or other unwanted soldering results.

5.5

Component Picking

The SCA3000 component can be picked from the carrier tape using either vacuum assist or

mechanical type pick heads. Typically a vacuum nozzle is used. Pick up nozzles are available in

various sizes and shapes to suit a variety of different component geometries. It is recommended

that different pick up nozzles are tested to find the best one. The polarity of the part must be

assured in taping process. The polarity of the part on tape is presented in figure 5 on page 4.

5.6

Component Placement

SCA3000 MID packages must be placed onto PWB accurately according to their geometry.

Positioning the packages manually is not recommended. Placement should be done with modern

automatic component pick & place machinery using vision systems.

Recognition of the packages automatically by a vision system enables correct centering of

packages.

5.7

Reflow Soldering

A forced convection reflow oven is recommended to be used for soldering SCA3000 components.

IR-based reflow ovens are not generally suitable for lead-free soldering. Figure 8 presents a

general forced convection reflow solder profile and it also shows the typical phases of a reflow

process.

The reflow profile used for soldering the SCA3000 package should always follow the solder paste

manufacturer's specifications and recommended profile. The typical ramp-up rate is 3°C/second

max. The reflow max. peak temperature (measured from the component body) should not exceed

260°C. The ramp down rate should be 6°C/second max.

VTI Technologies Oy

Subject to changes

9/15

www.vti.fi

TN54

Rev.C