AN1231 Motorola / Freescale Semiconductor, AN1231 Datasheet - Page 8

Manufacturer Part Number

AN1231

Description

Plastic Ball Grid Array (PBGA)

Manufacturer

Motorola / Freescale Semiconductor

Datasheet

1.AN1231.pdf (28 pages)

AN1231

although their current cost and image acquisition cycle time

may be prohibitive for some users. Fein Focus and Imaging

Systems International (affiliated with Nicolet) have both de-

veloped lower cost systems with the resolution to identify

voids and in some cases non-contact failures. Examples

imaged with the Fein Focus Model FXS-160.32 and Nicolet

Model NXR-1400, are presented in Figures 7 and 8, respec-

tively. Other systems with similar capabilities are available

from Lixi, I.R.T. and others.

A pad geometry design change that can allow detection of

Figure 7. X-ray Micrograph of a Mounted PBGA

Showing Voiding in the Solder Joints

Figure 6. X-ray Micrograph of a Mounted PBGA Showing Solder Shorting

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non-contact failures or opens involves modifying the mother-

board pad footprint. A tab or ear is placed in the soldermask

defined pad as in Figure 9. During reflow, solder fills the pad

and is readily observed by using even inexpensive x-ray sys-

tems. If solder plated or HASL motherboards are used or sol-

der paste is screened on prior to reflow, this ear would

already be filled with some solder. In these cases, the x-ray

would have to be of sufficient resolution to distinguish

between an ear filled by solder from the ball and one already

filled by plated, HASL’d or stenciled on solder.

Figure 9. PBGA Pad with Bump to Facilitate X-ray

Figure 8. X-ray Micrograph of a Mounted PBGA

X-RAY BUMP, EAR, OR TAB

Showing Solder Splattering/Balling

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Inspection

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MOTOROLA FAST SRAM