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The solution to Thermal Coefficient of Expansion (TCE) mismatch
A well documented industry problem is low solder joint reliability for
direct surface mounted packages subjected to thermal cycling. The difficulty
is that the ceramic package expands at a lower rate than the board, which is
typically glass-filled epoxy. The resulting stresses induced in the solder
cause solder joint rupture and electrical failure of the system. By standing
the package off the board with SolderQuik® CCMD's, stresses are spread over
a relatively long solder column, rather than focused on one small area. This
defocusing of stress eliminates solder joint fatigue and greatly improves
reliability.
Advantages to the Solderquik® CCMD
More Cost-Effective Than Constrained Core or Ceramic Boards
The CCMD mounting technique provides a lower cost, lighter weight solution to a
mismatch of the package TCE and the board material’s TCE compared to ceramic boards
or constrained core boards.
Easy Handling and Automated Assembly
Solder columns can take rougher handling than stamped "J" leads,
"C" leads, or "S" leads. An LCC with solder column attached can be
automatically fed and placed by surface mount robotics just like LCCs without columns.
Makes Cleaning and Inspection Easier
Because the components stand off the board, the CCMD mounting technique makes cleaning
and solder joint inspection easier than for direct surface mounted components. |
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1) CCMD: Water Dispersable Holder and Columns before
Reflow |
2) Chip carrier after CCMD columns have been attached and holder
removed. |
3) Completed Assembly reflowed to PWB |
Specifications
Physical Data
Number of columns: 20-84 (std. JEDEC configuration)
Column diameter: 15 and 22 mils
Center-center: 40 and 50 mils
Column height: 50 and 100 mils
Column material: reinforced solder
Holder material: Water dispersible paper laminate
Electrical Properties
Resistance: 1.2 mΩ/column
Capacitance: .38pF/column
Inductance: 2.4 nH/column
Propagation delay (calculated): 8.5 psec/100 mils
Test Results
Product Tested
Conventional: 68-pin leadless ceramic CC, surface-¬mounted directly to
FR-4 board using solder paste.
SolderQuik®: 68-pin leadless ceramic CC, mounted with CCMD to FR-4 board
Thermal Cycling Test: MIL-STD 883C, method 1010.4 temp. range: -55
to +125°C.
Result: Failure definition: first column increasing in R to ≥ 30mΩ.
Conventional: Less than 50 cycles.
SolderQuik®: 500 cycles min. (50 mil columns).
1000 cycles min. (100 mil columns).
Vibration Test: MIL-STD-1344A, method 2005.1, test condition VI,
Letter C, 3 axes, 8 hours each axis 10.2 G (RMS) random vibration at shaker
table. (Chip carrier acceleration of over 100 G's).
Result: Failure definition: same as for thermal test.
Conventional: No failures.
SolderQuik®: No failures.
Shock Test: 1 CCMD assembly.
MIL-STD 1344A, method 2004.1, conditions H, A, C, D; 5 shocks,
6 directions, at 30, 50,100, 300G.
Same part: MIL-STD 202F, method 213B, conditions E, F; 3 shocks, 6
directions,
0.6ms duration at 1000, 1500G.
Result: Failure definition: same as for thermal test.
Conventional: No failures.
SolderQuik®: No failures.
Transmission Characteristic: Signal applied at 300 MHz.
Result: From 10% to 90% of applied voltage.
Conventional: 4 nanoseconds
SolderQuik®: 4 nanoseconds
All of the above information, including illustrations, is believed to
be reliable. Users, however, should independently evaluate the suitability
of each product for their application. Winslow Automation, Inc. makes no
warranties as to the accuracy or completeness of the information, and
disclaims any liability regarding its use. Winslow Automation’s only
obligations are those in the Standard Terms and Conditions of Sale for this
product, and in no case will Winslow Automation, Inc. be liable for any
incidental, indirect, or consequential damages arising from the sale,
resale, use or misuse of the product.
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