|
|
 |
|
|
|
| |
|
|
Peak Reflow Times, Temperatures and the Impact of MSL on Johanson Ceramic Capacitors
John Maxwell, Director of Product Development
March 1, 2006
|
The change to lead free soldering with its corresponding increase in soldering
temperatures raises a number of assembly related process questions primarily because of
plastic package limitations.
- Maximum peak reflow temperature
- Time at peak reflow temperature
- Maximum number of assembly reflow cycles
- Maximum number of rework cycles
- MSL rating
Multi-layer ceramic capacitors (MLCC) do not have time and temperature limitations like
plastic molded components due to the construction of those capacitors. There are no
polymers or other temperature sensitive materials used minimizing the impact of
increased soldering temperatures.
Ceramic capacitors have been assembled without problems into leaded components for
decades using high temperature solders that have melting points as high as 309oC so lead
free peak temperatures of 260°C present no soldering temperature issues. This does not
mean that solder profiles can be ignored as there can be thermal shock cracking in wave
soldering or during assembly cool down. The solder process needs to be controlled but no
different that what is required for standard tin lead solder alloys.
The maximum time at temperature, number of reflow solder cycles or re-work cycles are
not limited by ceramic capacitors but by the assembly laminate and plastic molded
components. The board can blister, de-laminate and have plated thru hole failures. Plastic
molded components may crack or blister due to absorbed moisture. Those components
limit time at temperature and number of solder cycles, not the MLCC.
Due to the very nature and materials used in the manufacture of ceramic capacitors there
are no moisture absorbing materials used nor are there critical interfaces within the
MLCC that can crack or delaminate. This is not the case for PC boards and plastic
molded components that are moisture sensitive to water absorption of the plastics
themselves. MLC capacitors are MSL level 1 @ 260°C by construction and materials
used. |
| Notice: Specifications are subject to change without notice. Contact your nearest Johanson Dielectrics
Sales Office for the latest specifications. All statements, information and data given herein are believed
to be accurate and reliable, but are presented without guarantee, warranty, or responsibility of any kind,
expressed or implied. Statements or suggestions concerning possible use of our products are made
without representation or warranty that any such use is free of patent infringement and are not
recommendations to infringe any patents. The user should not assume that all safety measures are
indicated or that other measures may not be required. Specifications are typical and may not apply to all
applications. |
|
| Top |
|
|
|
|
