LMZ12,4yyy Generic 8D Report Datasheet by Texas Instruments

View All Related Products | Download PDF Datasheet
l TEXAS INSTRUMENTS
Semiconductor Group
Generic 8D REPORT
Power Module LMZ12xxx & LMZ14xxx
07/11/2014 - Rev. B
I TEXAS INSTRUMENTS mtg://www.ti.cum/Iit/an/snaaz14/snaa214.9d1 Solder Paste: Ref/ow Profile:
Generic 8D Report
Report Generated: 02/18/2014
Page 2 of 5
D1) TEAM MEMBERS:
Process Role
Name
Customer Quality Engineering Manager
Hartsell, Michelle
Packaging Engineering Manager
Prabhu, Ashok
Packaging Engineering Manager
Lim, CH
Package Engineering
Chua, CS
Failure Analyst
Huerta, Rafael
D2) PROBLEM DESCRIPTION:
TI has verified that some devices may exhibit solder extrusion causing failures during inline testing after
SMT. When solder extrusion bridges the neighboring bump (or die edge), it will result in electrical failure.
Below is the picture of the observed solder extrusion after parallel lapping.
D3) IMPLEMENT AND VERIFY CONTAINMENT ACTIONS:
TI implemented 1st Test ==> 1X Reflow @245C ==> 2nd Test to screen out marginal units (May 2012).
TI would also recommend customers to read the updated Power Module SMT guideline (SNAA214 -
http://www.ti.com/lit/an/snaa214/snaa214.pdf ) to minimize solder extrusion:
Solder Paste:
TI recommends the use of type 3 or finer solder paste when mounting on the board.
Reflow Profile:
Measure peak reflow temperature by placing a fine gauge thermocouple (Type K) on top of the
package body center.
Ensure the peak reflow temperature does not exceed 245°C max (240°C +/- 5°C). Exceeding the
max temperature may damage the part.
Reflow time within 5°C Peak Temp must not exceed 20 seconds
Reflow time above liquidus must not exceed 60 seconds
Minimizing the number of reflow cycles seen by the LMZxxx power module is recommended
I TEXAS INSTRUMENTS Moisture Hand/in .‘ Resistor Inductor Flip Chip on Lead
Generic 8D Report
Report Generated: 02/18/2014
Page 3 of 5
Moisture Handling:
LMZxxx Power Module is classified as MSL3 and requires special handling due to moisture
sensitivity. MSL 3 parts have a max floor life of 168 hours.
Parts must be reflowed prior to 168 hour floor life after removing from the moisture barrier bag.
Parts must be baked per JEDEC recommendations once the 168 hour floor life has been
exceeded.
D4) ROOT CAUSE:
The power module family of devices from Texas Instruments (TI) undergoes a complex assembly process
which involves passive components (inductor, resistors) along with a flip chip on lead bare die packaged
together.
TI has verified that some devices from lots may exhibit solder extrusion causing failures during inline
testing after SMT. When solder extrusion bridges the neighboring bump (or die edge), it will result in
electrical failure.
Solder extrusion requires a molten solder and a path for the solder to extrude into. The path is created by
a delamination between the mold compound and the die.
D5) IMPROVEMENT ACTIONS:
Improvement Actions
Owner
Date
1. Optimize de-flux process:
The process to clean off the flux residue after bump operation on
the flip chip die was optimized to ensure no flux residue is left
behind.
A/T Site
2. Bake after de-flux:
To further ensure that any remaining flux residue is inactivated; a
bake process using a dedicated oven was implemented.
A/T Site
3. Batch Plasma operation before mold: The weakness at the
interface of the mold compound and the flip chip die surface
provide a path for the solder to extrude during reflow. The plasma
process roughens the die surface enabling better adhesion of the
mold compound with this surface.
A/T Site
4. Use dedicated Oven for bake and dedicated machine for
Plasma operation. This prevents variations through contaminants
and helps achieve consistency.
A/T Site
5. TI has introduced an improved plasma process (Strip Plasma).
This process provides improved roughening quality and
homogeneous cleaning for the die surface which helps in better
A/T Site
I TEXAS INSTRUMENTS mtg://www.ti.com/Iit/an/snaa214/sna3214.gdf
Generic 8D Report
Report Generated: 02/18/2014
Page 4 of 5
Improvement Actions
Owner
Date
adhesion. Also, it provides improved control due to the reduced lot
size in the cleaning chamber as compared to the Batch Plasma
process.
6. Stainless Steel butterfly clip on flux wash jig. Previous clip made
out of aluminum based material coated with Zn caused Zn flakes to
deposit on die surface during flux clean.
A/T Site
7. Tuned Solder Paste Improvement. Improvements were made to
the mixing time of the solder paste to reduce the activity of the flux,
reducing the chance for mold compound delamination
A/T Site
Other factors that affect the delamination include reflow peak temperature and moisture absorption during
storage. TI would also recommend customers to read the updated Power Module SMT guideline
(SNAA214 - http://www.ti.com/lit/an/snaa214/snaa214.pdf ) to minimize solder extrusion.
Field Reliability:
The parts affected by solder extrusion will manifest as non-functional failures during customer
inline testing post SMT reflow process.
No further extrusion is expected if no additional high temperature process that is over ~220C is
present; this is the physical property of the internal solder.
The units that pass have not been observed to degrade under normal operating conditions based
on internal evaluation of this issue.
No field reliability failures have been reported to date over multiple batches.
Thermal Cycling was performed (-45 to 125C) on 45 units of material from affected lot after
subjecting these units to 4X reflow cycles. No TMCL failures were observed after 500 cycles
D6) VALIDATE CORRECTIVE ACTION:
Improvements were made in the manufacturing process to minimize solder extrusion and improve
outgoing quality.
Data suggests that all these improvements have helped address the high failure rate at the customer line
and not necessarily reduce it to zero.
I INSTRUMENTS DPPM by Date Code A , / \ , — shipments , —DPPM \/ 1224 1230 1236 1242 28 ZC 31 32 33 34 35 36 37 38 39 3A 3B 3C 41
Generic 8D Report
Report Generated: 02/18/2014
Page 5 of 5
The data was collected by data mining the shipment info and customer returns as of July 2014.
The graph shows the high DPPM rate in 2012. The shipments significantly increased in 2013 while the
DPPM rate has significantly reduced.
TI attribute this to continuous improvements implemented in TIEM (latest ones being Strip Plasma &
Stainless Steel butterfly jig) to make this package family more robust
D7) ACTION TAKEN TO PREVENT RECURRENCE:
See D5 & D6
D8) CONGRATULATE THE TEAM:
Strip Plasma &
SS Butterfly Clip
Optimized Batch
Plasma &
Dedicated Oven

Products related to this Datasheet

DC DC CONVERTER 0.8-3.6V
DC DC CONVERTER 0.6-3.6V
DC DC CONVERTER 0.6-3.6V 2W
DC DC CONVERTER 0.8-3.6V
DC DC CONVERTER 0.8-6V
DC DC CONVERTER 5-30V
DC DC CONVERTER 0.6-3.6V
DC DC CONVERTER 0.8-3.6V 4W
DC DC CONVERTER 0.8-6V
DC DC CONVERTER 0.8-6V
DC DC CONVERTER 0.8-6V
DC DC CONVERTER 0.8-6V
DC DC CONVERTER 0.8-6V
DC DC CONVERTER -3 TO -17V
DC DC CONVERTER 0.8-5V
DC DC CONVERTER 0.8-6V
DC DC CONVERTER 5-30V
DC DC CONVERTER 0.8-6V
DC DC CONVERTER 0.8-6V
DC DC CONVERTER 5-30V
DC DC CONVERTER 0.6-5.5V 22W
DC DC CONVERTER 0.6-3.6V 2W
DC DC CONVERTER 0.8-6V
DC DC CONVERTER 5-30V
DC DC CONVERTER 0.8-3.6V 14W
DC DC CONVERTER 0.6-5.5V 33W
DC DC CONVERTER 0.8-5V
DC DC CONVERTER 0.8-3.6V
DC DC CONVERTER 0.8-6V
DC DC CONVERTER 0.8-5V