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Quad Flat Package Integrated Circuit

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Quad Flat Package Integrated Circuit

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The Ceramic Quad Flat Pack, or CQFP, is a ceramic IC package with leads extending from all four sides of the package body. CQFP's are predominantly square in shape, although rectangular variants do exist. The CQFP is just one of the many types of the quad flat pack (QFP) package. The CQFP comes in many body sizes, with lead counts typically ranging from 28 to 352. Lead pitch values used by CQFP's range from 0.5 mm to 1.27 mm. Typical CQFP body thickness varies from 1.27 mm to 4 mm.

There are several CQFP chips in a computer including the CMOS RAM chip.

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As shown in the figure, a paraxial ray is incident

at point Q on a concave mirror.

q = angle of incidence = angle of reflection

= Ð CQF = Ð QCF ( by geometry )

So, for D CFQ,

exterior Ð QFP = Ð CQF + Ð QCF = 2q .

For paraxial incident ray and small aperture,

CP' » CP = R and FP' » FP = f.

For small aperture, 2q is very small.

\ from the figure, 2q »

FP

QP

=

f

QP

… ( 1 ) and q =

CP

QP

=

R

QP

… ( 2 )

From equations ( 1 ) and ( 2 ), R = 2f ⇒ f = R / 2

Thus, focal length of a concave mirror is half its radius of curvature.

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