PCF5079 datasheet(26/28 Pages) PHILIPS

26 / 28 page

2001 Nov 21

Philips Semiconductors

Product speciﬁcation

Dual-band power ampliﬁer controller for

GSM, PCN and DCS

PCF5079

15.2.3

STENCIL DESIGN FOR PERIMETER PADS

For optimum paste release the area and aspect ratios of

the stencil should be greater than 0.66 and 1.5

respectively.

where:

L = aperture length

W = aperture width

T = stencil thickness.

15.2.4

STENCIL DESIGN FOR THERMAL PADS

In order to remove the heat effectively from the package

and to enhance electrical performance the die-attach

paddle needs to be soldered to the PCB thermal pad,

preferably with minimum voids.

It is therefore recommended that smaller, multiple

openings in a stencil should be used instead of one large

opening for printing solder paste in the thermal pad region.

This results typically in 50% to 80% solder paste coverage.

Two examples are shown in Fig.21.

15.2.5

STENCIL THICKNESS

A stencil thickness of 0.125 to 0.150 mm is recommended

but this value needs to be optimized by the user to find the

proper thickness according to application requirements.

Area ratio

area of aperture opening

aperture wall area

-----------------------------------------------------------------

2T(L + W)

--------------------------

Aspect ratio

aperture width

stencil thickness

-------------------------------------------

-----

handbook, full pagewidth

MGW499

Fig.21 Examples of thermal pad stencil design.

a. Outline of 0.4 mm2 2

× 2 array giving

44% solder paste coverage.

b. Outline of 1.2 mm2 2

× 1 array giving

60% solder paste coverage.

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