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Ball Grid Array (BGA) Packaging 14
14.1 Introduction
The plastic ball grid array (PBGA) has become one of the most popular packaging alternatives for
high I/O devices in the industry. Its advantages over other high leadcount (greater than ~208 leads)
packages are many. Having no leads to bend, the PBGA has greatly reduced coplanarity problems
and minimized handling issues. During reflow the solder balls are self-centering (up to 50% off the
pad), thus reducing placement problems during surface mount. Normally, because of the larger ball
pitch (typically 1.27 mm) of a BGA over a QFP or PQFP, the overall package and board assembly
yields can be better. From a performance perspective, the thermal and electrical characteristics can
be better than that of conventional QFPs or PQFPs. The PBGA has an improved design-to-produc-
tion cycle time and can also be used in few-chip-package (FCPs) and multi-chip modules (MCMs)
configurations. BGAs are available in a variety of types, ranging from plastic overmolded BGAs
called PBGAs, to flex tape BGAs (TBGAs), high thermal metal top BGAs with low profiles (HL-
PBGAs), and high thermal BGAs (H-PBGAs).
The H-PBGA family includes Intel's latest packaging technology - the Flip Chip (FC)-style, H-PB-
GA. The FC-style, H-PBGA component uses a Controlled Collapse Chip Connect die packaged in
an Organic Land Grid Array (OLGA) substrate. In addition to the typical advantages of PBGA pack-
ages, the FC-style H-PBGA provides multiple, low-inductance connections from chip to package,
as well as, die size and cost benefits. By providing multiple, low-inductance connections the FC-
style, HPBGA offers equivalent or better performance than an extra on-chip metal layer. The FC
technology also provides die-size benefits through the elimination of the bond pad ring and better
power bussing and metal utilization. The OLGA substrate results in a smaller package, since there
is no cavity, and thermal management benefits since the thermal solution can directly contact the
die.
2000 Packaging Databook 14-1
Ball Grid Array (BGA) Packaging
14.2 Package Attributes
Table 14-1. PBGA Package Attributes
PBGA
Lead Count 196 208 241 256 256 304 324 421 468 492 544
(15mm) (23mm) (23mm) (17mm) (27mm) (31mm) (27mm) (31mm) (35mm) (35mm) (35mm)
Sq/Rect. S S S S S S S S S S S
Pitch (mm) 1.0 1.27 1.27 1.0 1.27 1.27 1.27 1.27 1.27 1.27 1.27
Package 1.61 2.33 2.38 1.56 2.13 2.33 2.13 2.38 2.38 2.38 2.38
Thickness (mm)
Weight (gm) .67 1.56 .70 3.46 2.86 3.87 5.06
Max. Footprint 15.20 23.20 23.20 17.20 27.20 31.20 27.20 31.20 35.20 35.20 35.20
(mm)
Shipping Media:
Tape & Reel X X X X X X X X
Trays X X X X X X X X X X X
Desiccant Pack X X X X X X X X X X X
Comments/
Footnotes
Table 14-2. H-PBGA/HL-PBGA Package Attributes
H-PBGA HL-PBGA
Lead Count 495 540 615 304 352 432
Sq/Rect. R S R S S S
Pitch (mm) 1.27 1.27 1.27 1.27 1.27 1.27
Package 2.54 2.13 2.54 1.54 1.54 1.54
Thickness (mm)
Weight (gm) 4.52 15.25 4.11 8.90
Max. Footprint 27.2 x 31.0 43.0 31.0 x 35.0 31.10 35.10 40.10
(mm)
Shipping Media:
Tape & Reel X X
Trays X X X X X X
Desiccant Pack X X X X X X
Comments/ Can be Can be Can be Can be
Footnotes thermally thermally thermally thermally
enhanced enhanced enhanced enhanced
with heat with heat with heat with heat
sinks sinks sinks sinks
14.3 Package Materials
The PBGA package consists of a wire-bonded die on a substrate made of a two-metal layer copper
14-2 2000 Packaging Databook
Ball Grid Array (BGA) Packaging
clad bismaleimide triazine (BT) laminate. Four-metal layer substrate designs generally contain ad-
ditional power and/or ground planes to improve electrical and thermal performance. The die and
bonds are protected and encapsulated with molding compound. Via holes drilled through the sub-
strate provide routing from the lead fingers to the respective eutectic (63/37 Sn/Pb) solder balls on
the underside. Thermal performance can be enhanced by adding heatsink fastened through mechan-
ical means using thermal grease or by using conductive epoxy.
The H-PBGA and HL-PBGA, however, are configured differently to provide for greater thermal and
if required, electrical performance. The thermal advantage provided by this design is based first
upon attaching the die to the bottom surface of a heatspeader or slug that also forms the topside of
the package. Secondly, because the copper heatspreader forms the top of the package, the thermal
resistance is extremely low and exposes the package surface to available air flow. If required, this
heatslug can be directly coupled to active or passive thermal management devices such as heat sinks
or heat pipes. Improved electrical performance is achieved through additional power and/or ground
planes.
The FC-style, H-PBGA package consists of a die reflowed onto an oraganic substrate. The substrate
consists of four to ten layers of copper with insulating materials in between. The copper layers are
connected by vias. BT (Bismaleimide Triazine) resin reinforced with glass fiber forms the core of
the organic substrate. Solder bumps (3% Sn, 97% Pb) on the die surface are joined with solder pads
(60% Sn, 40% Pb) on the organic substrate in a reflow furnace. These joints form the electrical/
mechanical connection between the FC die and the OLGA package. An epoxy underfill fills the gap
between die and the substrate. This underfill provides mechanical support and protection for the die-
to-package interconnects and also minimizes thermal stress on the die due to CTE (coefficient of
thermal expansion) mismatch with the substrate materials. The die backside is exposed allowing the
thermal solutions and thermal interface material to have direct contact with the die surface.
See Figure 14-1, Figure 14-2, and Figure 14-3 for description of PBGA, HL-PBGA, and FC-style
H-PBGA packages.
Figure 14-1. PBGA Die Up Cross-Section
BT PCB
Die Up Design Mold Compound
Non-laminate
Solder Balls
A5764-01
2000 Packaging Databook 14-3
Ball Grid Array (BGA) Packaging
Figure 14-2. HL-PBGA Die Down Cross-Section
Copper Slug/Heatspreader BT PCB Laminate
Die Down Design Solder Balls
Encapsulant
A5765-01
Figure 14-3. FC-Style, H-PBGA Die Up Cross-Section
C4 Bumps Die-up Design
BT Lamintate Underfill
Solder balls
A7428-01
14-4 2000 Packaging Databook
Ball Grid Array (BGA) Packaging
14.4 Package Dimensions
Table 14-3. Plastic Ball Grid Array Family Attributes
Package Family Attributes
Category Plastic Ball Grid Array
Acronym PBGA, HL-PBGA, H-PBGA
Ball Counts PBGA: 196, 208, 241, 256, 304, 324, 421, 468, 492, 544.
HL-PBGA: 352, 304, 432.
H-PBGA: 540.
FC-style, H-PBGA: 495, 615.
Ball Material Solder (63/37)
Ball Pitch 1.0, 1.27 mm
Board Assembly Type Surface Mount
Table 14-4. Symbol List for Plastic Ball Grid Array Family
Letter or Symbol Description of Dimensions
A Overall Height
A1 Stand Off
A2 Encapsulant Height
A3 Die Height with FC Bumps and Underfill
b Ball Diameter
c Substrate Thickness
D Package Body Length
D1 Encapsulant Length
E Package Body Width
E1 Encapsulant Width
F1 Die Width
F1 Die Length
e Ball Pitch
N Ball Count i.e. Lead Count
S1 Outer Ball Center to Short Edge of Body
S2 Outer Ball Center to Long Edge of Body
NOTE:
1. Controlling Dimensions: Millimeter
2000 Packaging Databook 14-5
Ball Grid Array (BGA) Packaging
Figure 14-4. PBGA Package Ball Array Configuration
Pin #1 Pin #1
Corner Corner
PBGA 196 PBGA 208
Pin #1 Pin #1
Corner Corner
PBGA 241 PBGA 256 (17mm)
Pin #1 Pin #1
Corner Corner
PBGA 256 (27mm) PBGA 304
A5487-03
14-6 2000 Packaging Databook
Ball Grid Array (BGA) Packaging
Figure 14-5. PBGA Package Ball Array Configuration Continued
Pin #1
Corner Pin #1
PBGA 324 Corner
PBGA 421
Pin #1 Pin #1
PBGA 468 Corner PBGA 492 Corner
Pin #1
Corner
PBGA 544 (35mm)
A6124-02
2000 Packaging Databook 14-7
Ball Grid Array (BGA) Packaging
Figure 14-6. 15mm PBGA Outline Drawing
15.00