SCA3000 Assembly Instructions

5

Printed Wiring Board (PWB) Level Guidelines

5.1

Land Pad Design

Two types of land patterns are used for surface mount packages:

1) Non-Solder Mask Defined Pads (NSMD)

2) Solder Mask Defined Pads (SMD).

NSMD pads have an opening which is larger than the pad itself, and SMD pads have a solder

mask opening that is smaller than the metal pad on PWB. NSMD is preferred since the copper

etching process has tighter process control compared to the solder mask process. The specific

PWB land pattern for the SCA3000 component is presented in figure 7.

Figure 7.

Recommended PWB pad layout for SCA3000 component.

VTI's SCA3000 packages can be soldered on commonly used substrates, e.g. FR-4, ceramic etc.

The pad metallization should be solder wettable in order to assure good quality solder joints. For

fine pitch assembly, the quality of plating is important. Generally used circuit board finishes for fine

pitch SMD soldering are NiAu, OSP, Electroless-Ag and Electroless-Sn.

5.2

Solder Paste

The SCA3000 package can be soldered with lead-free SAC (tin-silver-copper) solder. The SAC

solder paste composition should be near eutectic. The melting point of lead-free SAC solder can

vary between 217–221ºC, depending on the composition of solder alloy. In order to guarantee full

RoHS compatibility lead-free solder should be used for the soldering of VTI's SCA3000 component.

Also traditional eutectic SnPb solder can be used for soldering the SCA3000 packages if a lead-

free process is not required. With the eutectic SnPb solder, the melting point is 183°C.

A no-clean solder paste is recommended, since the SCA3000 package has very small stand off

and the effectiveness of cleaning process is therefore low. Ultrasonic agitation wash is not

allowed. The solder paste which is used must be suitable for printing it through the stencil aperture

dimensions. Type 3 paste is recommended (grain size 25-45mm).

7.25 mm

Pitch

0.80 mm

0.976 mm

2.25 mm

0.55 mm

0.25 mm (minimum

recommended clearance)

Component lead

(gray)

PWB land

(green)

0.10 mm (extension of

PWB land towards

center of the package)

0.15 mm (extension of PWB land

towards outside of the package)

0,025 mm (extension of

PWB land on both sides)

VTI Technologies Oy

Subject to changes

8/15

www.vti.fi

TN54

Rev.C