IPC-7095C-2013.pdf - 第34页

4.3.1.3 Fine Pitch Rectangular BGA Package JEDEC Publication JEP95, Section 4.6 deﬁnes a ﬁne-pitch, rectan- gular ball grid array (FRBGA) has an array of metallic balls on the underside of the package. The substrate or c…

4.2.2 Flip Chip The ﬂip chip (or direct-chip-attach)

design eliminates the need for wires and die attach. In this

design, the pre-bumped die is ﬂipped circuit side down and

the lands on the circuit side of the die are brought into

contact with corresponding lands on a substrate using sol-

der or conductive adhesive. The die bond pads, however,

are not immediately compatible with either solder or con-

ductive adhesive attachment processes. Solder bumping

with a solder compatible alloy composition before the die

wafer is sawed is one of the most common procedures. The

solder material and the bumped-pad structure materials are

chosen to optimize electrical and mechanical connection

typical of that shown in Figure 4-4.

Conductive adhesive or polymer attachment can be adapted

as well; however, the die bump contact may require a

‘‘noble’’ alloy that is compatible with the conductive alloy

particles in the adhesive. This alloy bump or ball can be

applied to the die bond pads by plating or ball bonding

processes. If a solder or an isotropic conductive adhesive is

used, the gap between the die and the substrate may require

an under-die-ﬁlling with epoxy to ensure mechanical integ-

rity of the die-to-substrate interface. Use of an anisotropi-

cally conductive material eliminates the need for added

underﬁll. After attaching the die to the substrate, it is typi-

cally encapsulated, coated, or over-molded for protection.

4.3 Standardization Standardization of BGA packaging

has considered a number of physical variables including

the diameter of the individual ball, the positional accuracy

of the ball in relationship to a true position within the com-

ponent outline.

4.3.1 Industry Standards for BGA For more detail

regarding package variation, mechanical feature dimen-

sions and allowable physical tolerances, refer to the follow-

ing JEDEC developed guidelines for BGA packaging.

4.3.1.1 BGA Package JEDEC Publication JEP95,

Section 4.14 deﬁnes a ball and column grid array package

family. A ball grid array (BGA) package or column grid

array (CGA) is a square or rectangular 1.50, 1.27, and

1.00 mm pitch package with an array of metallic balls or

columns on the underside of the package. The main body

of the package has a metallized circuit pattern applied to a

dielectric structure. To this package body, the semiconduc-

tor die(s) are attached to either the top or bottom surface.

On the underside of the dielectric is an array pattern of

metallized balls/columns which form the mechanical and

electrical connection from the package body to a mating

feature such as a printed circuit board. The surface that

contains the die may be encapsulated by various techniques

to protect the semiconductor.

4.3.1.2 Fine Pitch BGA Package JEDEC Publication

JEP95, Section 4.5 deﬁnes an FBGA package as a reduced-

pitch (<1.00 mm) version of a BGA package. The carrier

body of the package has a metallized circuit pattern applied

to a dielectric structure. One or more semiconductor

devices are attached to either the top or the bottom surface

of this dielectric carrier. On the underside of the dielectric

carrier is an array pattern of metallized balls, which form

the mechanical and electrical connection from the package

body to a mating feature such as a printed circuit board.

The surface that contains the die may be encapsulated

by various techniques to protect the semiconductor.

The requirements for a square FBGA package family

allows three optional contact pitch variations: 0.50, 0.65,

and 0.80 mm and deﬁnes four device proﬁle (height) varia-

tions as well. Additionally, a 0.75 mm contact pitch has

been included on the Die Size BGA (DSBGA) package

guideline, thus providing four pitch variations for the die

size device family.

The total proﬁle height of the FBGA as measured from the

seating plane to the top of the component is >1.70 mm. The

low-proﬁle ﬁne-pitch ball grid array (LFBGA) is a

reduced-height version of an FBGA. The total proﬁle

height of the LFBGA as measured from the seating plane

to the top of the component is no greater than 1.20 mm.

Thin proﬁle ﬁne pitch ball grid array (TFBGA) is a

reduced-height version of an FBGA with a total proﬁle

height as measured from the seating plane to the top of the

component that does not exceed 1.00 mm and the very thin

proﬁle ﬁne pitch ball grid array (VFBGA) is a reduced-

height version of an FBGA with a total proﬁle height as

measured from the seating plane to the top of the compo-

nent that is at or below 0.80 mm.

The JEDEC design guide for FBGA allows the manufac-

turer the option to increase ball diameter as the spacing or

pitch between ball contact centers increase as compared in

Table 4-1. The JEDEC FBGA and FRBGA design guide

does not support the 0.75 mm pitch; however, the industry

has registered some nonconforming parts with that pitch.

These are non-JEDEC packages.

The larger ball diameter option has been allowed to accom-

modate packages using rigid interposer structures. The

larger diameter ball may compensate, to a degree, for the

wide mismatch of the coefficient of thermal expansion

(CTE) between the silicon die and the rigid PCB structure.

IPC-7095c-4-4

Figure 4-4 Flip-Chip (Bumped Die) on BGA Substrate

Heat Spreader

Thermal Paste

Flip Chip Solder Balls

Package Substrate

BGA Solder Balls

Circuit Board

Underfill

Die

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4.3.1.3 Fine Pitch Rectangular BGA Package JEDEC

Publication JEP95, Section 4.6 deﬁnes a ﬁne-pitch, rectan-

gular ball grid array (FRBGA) has an array of metallic

balls on the underside of the package. The substrate or car-

rier of the package has a rectangular shape with a metal-

lized circuit pattern applied to either or both sides of a

dielectric structure. Generally described with the same gen-

eral terms noted in the JEP95, Section 4.5, the body size

for an FRBGA is deﬁned by the D and E dimensions.

Dimension D is the size of the body when measured paral-

lel to the major axis of the package, and dimension E is the

size measured parallel to the minor axis. Thus, for rectan-

gular packages, D will have a larger value than E.

4.3.1.4 Die Size BGA Package JEDEC Publication

JEP95, Section 4.7 deﬁnes a die-size ball grid array

(DSBGA) package. A Die-size Ball Grid Array has an array

of metallic balls on the underside of the package. The sub-

strate or carrier of the package may have a square or rect-

angular shape with a metallized circuit pattern applied to

either or both sides of a dielectric structure. The semicon-

ductor die is attached to the top surface of this dielectric

carrier. On the underside of the dielectric, the array pattern

of metallized balls provides the mechanical and electrical

connection from the package body to the next level com-

ponent such as a printed circuit board. The surface to

which the die is attached may be encapsulated by various

techniques to protect the semiconductor. The size of the

substrate or carrier is as close to the die size as practically

possible.

A ‘‘die-size’’ ball grid array (DSBGA) is a type of BGA

package where the body size is deﬁned to coincide as

closely as possible with a speciﬁc die size. This package is

sometimes called a ‘‘real chip-size’’ BGA or CSP. The

dimensions of the package body accommodate assembly

only of a die with a speciﬁc size, and these body dimen-

sions will change as a result of future changes in die size.

The outline of the package may be square or rectangular,

but this aspect ratio may also change as a given package is

redesigned to conform to a new die size. The aspect ratio

will likely differ for devices of the same functionality from

multiple suppliers. The controlling factor for the standard-

ization of DSBGA packages is the size and aspect ratio of

the ball array.

The D and E dimensions deﬁne the body size for a DSBGA

package. For packages with a rectangular ball matrix, the

matrix determines the orientation of the dimensions.

Dimension D is the body size measured parallel to the

major axis of the ball matrix, and dimension E is the body

size measured parallel to the minor axis of the ball matrix.

Thus for rectangular packages, D will not necessarily have

a larger value than E as would be the case for an FRBGA

package per JEDEC JEP95, Section 4.6. A DSBGA pack-

age with a square ball matrix should follow the usual

JEDEC convention where D is greater than E. The maxi-

mum values for both D and E are deﬁned in JEDEC Pub-

lication 95 using 0.50 mm increments. The values are

determined by rounding the actual DSBGA body size

upward to the next 0.50 mm boundary. Thus, D and E val-

ues have the form y.00 or y.50 following this procedure.

The array pitch for a DSBGA package will not necessarily

be equal for the D and E matrix dimensions. When the

pitches are not equal, ball dimensions and tolerances for

the smaller of the two pitches will govern the deﬁnition of

related package dimensions and tolerances. The controlling

pitch of the array of balls on a DSBGA package is always

less than 1.0 mm. The contact pitch variations for the

DSBGA described in JEP95, Section 4.7, are 0.80, 0.75,

0.65 and 0.50 mm.

4.3.2 Ball Pitch Ball Grid Arrays are divided up into two

groups of pitches. The ﬁrst group includes both plastic and

ceramic package outlines allowing 1.50, 1.27, and 1.00 mm

contact pitch variations. The second group is designated

as a ﬁne-pitch and die size BGA package family allowing

ball contact pitch variations of 0.80, 0.75, 0.65, 0.50, 0.40,

0.30, and 0.25 mm for the die size BGA. Few component

manufacturers are currently providing parts with 1.5 mm

pitch, as the pressure is on form factor in order to keep

BGAs as small as possible and although ball pitch of

0.40 mm and less are allowed, the applications may be

limited for conventional surface mount assembly due to

difficulty in processing. Pitch plays a large role in the deter-

mination of what ball diameters can be used in various

combinations. Table 4-2 shows the characteristics of those

balls that are used with pitches of 0.5 mm through 1.5 mm

for PBGAs while Table 4-3 shows the future balls for

DSBGAs.

Table 4-1 JEDEC Standard JEP95-1/5

Allowable Ball Diameter Variations for FBGA

Ball Pitch

Ball Diameter/mm

Min. Nom. Max.

0.50 0.25 0.30 0.35

0.65 0.25 0.30 0.35

0.65 0.35 0.40 0.45

0.80 0.25 0.30 0.35

0.80 0.35 0.40 0.45

0.80 0.45 0.50 0.55

Table 4-2 Ball Diameter Sizes for PBGAs

Nominal Ball

Diameter (mm)

Tolerance

Variation (mm) Pitch (mm)

0.75 0.90 - 0.65 1.5, 1.27

0.60 0.70 - 0.50 1.0

0.50 0.55 - 0.45 1.0, 0.80

0.45 0.50 - 0.40 1.0, 0.80, 0.75

0.40 0.45 - 0.35 0.80, 0.75, 0.65

0.30 0.35 - 0.25 0.80, 0.75, 0.65, 0.50

IPC-7095C January 2013

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Although not mandatory, nonsymmetrical ball patterns

have the added advantage of enabling automated orienta-

tion detection during assembly. One example is to omit one

of the corner balls in an otherwise symmetrical array.

4.3.2.1 Future Ball Contact Size Conditions Although

not required for the BGAs shown in Table 4-2, future ball

sizes contemplated are shown in Table 4-3.

4.3.2.2 Land Pattern Approximation The land pattern of

the component substrate (where the ball is attached) and

the land pattern of the mounting structure (printed board)

should be as similar in diameter as possible. Component

manufacturers have determined that the printed board land

pattern or the pad on the component should be slightly less

than the ball diameter. The amount of reduction is based on

the original ball size, which is used to determine the aver-

age land. In determining the relationship between nominal

characteristics, a manufacturing allowance for land size has

been determined to be 0.1 mm between the maximum

material condition (MMC) and least material condition

(LMC) for ball diameters of 0.40 mm and above and less

for balls that are smaller.

The information shown in Table 4-4 provides data on land

patterns and their variation to accommodate nine ball

diameters.

Many component manufacturers use solder mask-deﬁned

lands (see 6.2.2). When this technique is employed, the

nominal land diameter should be increased by the amount

of solder mask encroachment on the land (usually about

0.1 mm). The opening in the solder mask window then

represents the diameter to which the ball will become

attached, while the actual land is slightly larger to accom-

modate the solder mask-deﬁned land concepts. It should be

noted that routing density is decreased, since the land is

larger.

4.3.3 BGA Package Outline Body sizes for ball grid

arrays are divided up into the following two outline groups:

square and rectangular. The square outline package family

size ranges from as small as 4 mm x 4 mm and as large as

50 mm x 50 mm. In the ﬁne pitch variations, the package

sizes increase in 1.0 mm increments. In the ranges above

21 mm x 21 mm, the body size increases in increments of

2.0 mm to 2.5 mm and the pitches are in the regular range.

Rarely will any of the ﬁne pitch parts be found in sizes

larger than 21 mm x 21 mm. The rectangular BGA family

has the same size ranges from 4.0 mm to 50 mm but varies

by each application. This group can have many more varia-

tions than the square group. Rectangular sizes typically are

found to follow no ﬁxed incremental progression. This

group is normally driven by the memory applications and

closely follows the die sizes. Rectangular sizes are nor-

mally standardized in small application speciﬁc families.

The ﬁne pitch BGA components, equal to or less than 0.8

mm, rarely exceed 21 mm in body size.

A ﬁne pitch ball grid array (FBGA) is a 0.50 to 0.80 mm

pitch solder balled array package that have ﬁxed package

dimensions ‘‘D (Length)’’ and ‘‘E (Width).’’ The FBGA is

more like the plastic and ceramic BGA families described

above having ﬁxed body dimensions. Although the FBGA

outline is typically only 20% larger than the die, it will not

change shape with every die shrink.

The die-size ball grid array package (DSBGA) is a 0.30 to

0.50 mm pitch solder balled array package that has variable

package dimensions ‘‘D (Length)’’ and ‘‘E (Width).’’ The

DSBGA package takes the shape of the die which normally

makes it a rectangular outline and is presently widely used

in Flash and DRAM Memory devices. The rectangular die

size (RDS) outline will likely change ‘‘D’’ and ‘‘E’’ dimen-

sions with every die shrink.

4.3.4 Ball Size Relationships The total variation of the

system considers three major issues: positioning, ball toler-

ance, and substrate tolerance. All three attributes added

together result in a worst case analysis; however, as with

other land patterns in the standard, a statistical average is

determined by using the RMS (root mean, square) value.

The trend toward higher pin-count ICs and smaller package

outlines has enabled companies to improve both product

functionality and performance. Table 4-5 will assist the

user in calculating variations in land pattern geometry for a

wide range of BGA applications, and shows the total varia-

tion in the system for each of the nine ball sizes identiﬁed

in the standards. As noted, the standard nominal dimension

for ball contact diameters are 0.15, 0.20, 0.25, 0.30, 0.40,

0.45, 0.50, 0.60, and 0.75 mm. Ball contact size for array

packages are inﬂuenced by the limit established for overall

package height, ball contact pitch and the desire to maxi-

mize solder joint reliability.

Table 4-3 Future Ball Size Diameters for DSPBGAs

Nominal Ball

Diameter (mm)

Tolerance

Variation (mm) Pitch (mm)

0.25 0.28 - 0.22 0.40

0.20 0.22 - 0.18 0.30

0.15 0.17 - 0.13 0.25

Table 4-4 Land Size Approximation

Nominal Ball

Diameter (mm) Reduction

Nominal Land

Diameter (mm)

Land

Variation (mm)

0.75 25% 0.55 0.60 - 0.50

0.60 25% 0.45 0.50 - 0.40

0.50 20% 0.40 0.45 - 0.35

0.45 20% 0.35 0.40 - 0.30

0.40 20% 0.30 0.35 - 0.25

0.30 20% 0.25 0.25 - 0.20

0.25 20% 0.20 0.20 - 0.17

0.20 15% 0.15 0.15 - 0.12

0.15 15% 0.10 0.10 - 0.08

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