pcf8564a NXP Semiconductors, pcf8564a Datasheet - Page 39

• Manufacturer Part Number: pcf8564a
• Description: Real Time Clock And Calendar
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCF8564A_1
Product data sheet
19.3.1 Stand off
19.3.2 Quality of solder joint
19.3.3 Rework
For further information on temperature profiles, refer to application note AN10365
“Surface mount reflow soldering description” .
The stand off between the substrate and the chip is determined by:
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.
Fig 34. Temperature profiles for large and small components
•
•
•
The amount of printed solder on the substrate
The size of the solder land on the substrate
The bump height on the chip
temperature
MSL: Moisture Sensitivity Level
Rev. 1 — 8 October 2009
= minimum soldering temperature
maximum peak temperature
minimum peak temperature
= MSL limit, damage level
Real time clock and calendar
temperature
peak
PCF8564A
© NXP B.V. 2009. All rights reserved.
001aac844
time
39 of 44