PCA9901DP NXP [NXP Semiconductors], PCA9901DP Datasheet - Page 24

• Manufacturer Part Number: PCA9901DP
• Description: One wire single LED driver
• Manufacturer: NXP [NXP Semiconductors]

NXP Semiconductors
17. Abbreviations
PCA9901_1
Product data sheet
16.3.2 Quality of solder joint
16.3.3 Rework
16.3.4 Cleaning
The higher the stand off, the better the stresses are released due to TEC (Thermal
Expansion Coefficient) differences between substrate and chip.
A flip-chip joint is considered to be a good joint when the entire solder land has been
wetted by the solder from the bump. The surface of the joint should be smooth and the
shape symmetrical. The soldered joints on a chip should be uniform. Voids in the bumps
after reflow can occur during the reflow process in bumps with high ratio of bump diameter
to bump height, i.e. low bumps with large diameter. No failures have been found to be
related to these voids. Solder joint inspection after reflow can be done with X-ray to
monitor defects such as bridging, open circuits and voids.
In general, rework is not recommended. By rework we mean the process of removing the
chip from the substrate and replacing it with a new chip. If a chip is removed from the
substrate, most solder balls of the chip will be damaged. In that case it is recommended
not to re-use the chip again.
Device removal can be done when the substrate is heated until it is certain that all solder
joints are molten. The chip can then be carefully removed from the substrate without
damaging the tracks and solder lands on the substrate. Removing the device must be
done using plastic tweezers, because metal tweezers can damage the silicon. The
surface of the substrate should be carefully cleaned and all solder and flux residues
and/or underfill removed. When a new chip is placed on the substrate, use the flux
process instead of solder on the solder lands. Apply flux on the bumps at the chip side as
well as on the solder pads on the substrate. Place and align the new chip while viewing
with a microscope. To reflow the solder, use the solder profile shown in application note
AN10365 “Surface mount reflow soldering description”.
Cleaning can be done after reflow soldering.
Table 10.
Acronym
CDM
ESD
GPRS
GSM
HBM
LED
MM
PWB
•
The bump height on the chip
Abbreviations
Description
Charged Device Model
ElectroStatic Discharge
Global Packet Radio System
Global System for Mobile communications
Human Body Model
Light Emitting Diode
Machine Model
Printed Wiring Board
Rev. 01 — 3 December 2009
One wire single LED driver
PCA9901
© NXP B.V. 2009. All rights reserved.
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