IPC-7095C-2013.pdf - 第35页

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 ar…

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

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

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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

January 2013 IPC-7095C

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

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4.3.5 Package-on-Package BGA The package-on-

package (PoP) innovations are proving to be preferred for

a broad range of SiP applications. User companies have

realized that complex mixed-technology functions can be

produced with higher yield and more economically if the

semiconductors are individually prepackaged and tested

before joining. The most common solution for PoP appli-

cations utilizes package sections designed around the exist-

ing JEDEC FBGA standard array packaging format (see

Figure 4-5). Stacking prepackaged die has less risk because

the individual packages are fully tested before conversion

to the stacked PoP format.

Whether or not to join one package to the other before or

during the board level assembly process is a decision that

may be inﬂuenced by the requirement for in-process con-

ﬁguration ﬂexibility. For example, the base package can be

furnished by vendor ‘‘A’’ while the memory sections of the

stack are supplied by vendor ‘‘B,’’ ‘‘C’’ or ‘‘D.’’ After all,

memory functions are available from a greater number of

sources and the testing for memory is somewhat special-

ized. Furthermore, the concern of ownership of total qual-

ity and reliability can be alleviated. The logic device sup-

plier is responsible for the logic, the memory

manufacturers are responsible for the respective memory,

and the board assembler is responsible for only the surface

mount attachment of the two. This alternative has two ben-

eﬁts. It allows the user to specify multiple variations (dif-

ferent memory functions, data rate and so on) as well as

accommodating secondary sources of supply.

4.3.6 Coplanarity A critical issue in surface mount

packages is the limits for coplanarity of the contacts. The

coplanarity requirements in a BGA package are very differ-

ent from other lead-frame packaged surface mount compo-

nents. Coplanarity for any BGA is the distance of compo-

nent contact surface above a common seating plane. Thus

noncoplanarity, a simpliﬁed term, is the maximum distance

between the lowest and the highest contact when the pack-

age rests on a perfectly ﬂat surface. This deﬁnition repre-

sents a package sitting on a PC board on at least three

locations.

Coplanarity tolerance deﬁnes the distance from the seating

plane to the highest point of the package. This dimension

includes the standoff height, package body thickness and

(if present) lid thickness. The measurement criteria do not

include attached features such as heat sinks or other com-

ponents. An integral heat-slug, however, is not considered

an attached feature. If the package happens to be laminate

substrate based BGA, additional coplanarity issues can be

expected due to problems associated with adapting larger

substrates and maintaining ﬂatness within the tolerances.

This, in part, is the reason why the plastic BGA (PBGA)

package coplanarity requirement is established at 150 µm.

Most suppliers would like the allowable BGA coplanarity

limit to be around 200 µm but the users would prefer the

maximum to be no greater than 100 µm (see 4.6.2.6 and

4.8.4). There are different coplanarity requirements for dif-

ferent types of BGAs. Table 4-6 shows a sampling of

JEDEC registered BGA package outlines.

The coplanarity values may vary from JEDEC outline-to-

outline because of the ball metallurgy. In low temperature,

eutectic (183°C melting point) solder balls, the balls

Table 4-5 Land-to-Ball Calculations for Current and Future BGA Packages (mm)

Land Size

Location

Allowance

Ball

Variation

Ball Size

% Reduction

from Nom.

Variation

AllowanceMMC LMC Nominal MMC LMC

0.60 0.50 0.10 0.25 0.75 0.90 0.65 25% 0.25

0.50 0.40 0.10 0.20 0.60 0.70 0.50 25% 0.20

0.45 0.35 0.10 0.10 0.50 0.55 0.45 20% 0.17

0.40 0.30 0.10 0.10 0.45 0.50 0.40 20% 0.17

0.35 0.25 0.10 0.10 0.40 0.45 0.35 20% 0.17

0.25 0.20 0.05 0.10 0.30 0.35 0.25 20% 0.15

0.20 0.17 0.05 0.06 0.25 0.28 0.22 20% 0.08

0.15 0.12 0.05 0.04 0.20 0.22 0.18 15% 0.07

0.10 0.08 0.05 0.04 0.15 0.17 0.13 15% 0.07

IPC-7095c-4-5

Figure 4-5 JEDEC Standard Format for Package-on-

Package Components Source: JEDEC Publication 95-4.22

= 0.65 mm

0.50 mm

0.65 mm

0.80 mm

0.50 mm

Table 4-6 Examples of JEDEC Registered BGA Outlines

Registered Outline Package Type Coplanarity

MO-151 Plastic BGA 0.20 mm

MO-156/MO-157 Ceramic BGA 0.15 mm

MO-195 Fine Pitch BGA 0.08 mm

IPC-7095C January 2013

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

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