BGA Layout While Designing Your Printed Circuit Board

BGA Layout for ease of use

Presenter
Mike Galloway
Manufacturing Engineer

Overview
 Introduction

 BGA Capability

 BGA History

 DFM Standards

 Technologies

 Design Thermal Management

 Trace Routing and Vias

Introduction
Mike Galloway’s Experience:
 18 years in electronics manufacturing.

 Technical Support Team Manager for
Screaming Circuits.

Screaming Circuits History:
 Established in 2003.

 Assemble tens of thousands of boards with BGA
components a year.

 Screaming Circuits and it’s parent company MEC
share 50 years of PCB assembly experience.

BGA Experience

Solder Paste: Package
Solder Jet Printing
Standard Stencil Paste Application on Package:
Two BGA’s stacked.

Fig. 4
www.mydata.com Fig. 3

Hybrid Process Micro BGA:
Mixed Alloys Less than .5mm

www.laocsmta.org Fig. 5
Fig. 6

BGA History

Developed in late 1980’s, gained popularity in 1990’s, and
wide spread use in 2000’s.

More complicated IC’s mean more I/O.

 Real estate is at a premium, therefore smaller package
types are becoming more common.

 .5mm pitch and smaller is being used more.

 Package on Package (POP) gaining popularity. Extensive
use in the mobile device market.

Standards
Recommended reads:

 IPC-7095B Design and Assembly Process
Implementation for BGAs

 IPC- 7351A Land pattern standard

 IPC-A-610E Acceptability of Electronic
Assemblies

 IPC-J-STD-001E Requirements for Soldered
Electrical and Electronic Assemblies

http://www.ipc.org

Technologies

Ball Alloy and its effect on assembly.

Mixed Technology:

 Lead free BGA and leaded solder.
 Some good history in the industry.
 Alloy seems to be somewhat reliable for
commercial applications.
www.jovy-sys.com Fig. 10

 Leaded BGA and lead free solder. (Not recommended)
 Voiding.
 Alloy issues.
 Part integrity compromised due to heat.

Avoid mixing if possible. Stick with what is reliable and easy.

Designs

Micro BGAs and the challenges
around them:
 Larger dense parts nearby.
 Issues with profiling.

 Small pads.
 SMDP (Solder Mask Defined Pad) www.polarinstruments.com Fig. 11

 Trace routing:
 Via in pad. (Fig. 12)

Fig. 12

Designs
Package on Package (POP):
 Limited experience in prototypes.
 Requires significant process
development.

 Things to consider while designing:
 Adjacent Components
 PCB Stack up

 Process development:
 Part warping causing defects or long
term reliability issues.

Surface Finish Choices

• HASL - Micro BGA not recommended due to coplarinarity variations. (Fig. 14)

• ENIG - Needs good plating controls. Most vendors watch this very close. (Fig. 15)

• IMAg - Some concerns with microvoids. (Fig. 16)

Fig. 14 Fig. 15 Fig. 16

Thermal Management
Ground/thermal pad under package:
 Effects of inner ball reflow. (Fig. 17)
 Voiding in pad causing insufficient heat transfer.
 Vias in ground pad leaching solder away from the
die and down the vias. (Fig. 18)

Fig. 17 Fig. 18

Trace Routing and Vias
Designs that try to keep everything on few layers:

 Routing between pads. (Fig. 19)

 Connecting a series of pads. (Fig. 20)
 Using a thick trace, mask defined pads
 Oversize or undersize pads, or a combination of both on one BGA

Fig. 19 Fig. 20

Summary

 Best guide for DFM standards is IPC-7095B.

 BGA’s are becoming unavoidable and require more knowledge
for manufacturability.

 Learn more, ask questions:
 Go to SMTA meetings
 www.ipc.org
 http://www.element14.com/community/groups/screaming-circuits
 mgalloway@screamingcircuits.com

Thank you for joining us.

Questions?

BGA Layout While Designing Your Printed Circuit Board

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