TEMPERATURE Room Temp Copper and Solder particles suspended in polymer resin system [epoxy]
[2] Copper Particles Cu
Cu
Sn
[3] Polymer Matrix [Epoxy-based]
Cu Liquid Phase Sn Alloy Temperature 180-220C Alloy begins to melt (liquid phase)
Cu
Cu
Sn
Cu Sintered metal network
Temperature >225C Sn-Cu sintering reaction occurs
Sn-Cu Alloy Melt Point > 400C
Sn Cu
Cu Sn
Sn Cu Sn
SINTERED MICROSTRUCTURE
Benefits of Transient Liquid Phase Sintering Technology • Low temperature metallic joining – Can be processed in box oven or tunnel reflow
• Thermally stable at elevated temperatures – Will not remelt after sintering is complete
• Superior mechanical properties at elevated temperatures – Metallic bonds have higher strength compared to adhesives
• Pb-free & Halogen-free composition – Copper and Tin alloys
• Excellent Electrical and Thermal Conductivity – 10% shift
Rdson (m-ohm)
11.7
Source: Prismark
11.2 5-10% shift
10.7
0-5% shift
10.2
9.7 Initial
MSL 1 PbSn
1000 T-cycle C
TLPS
TLPS materials have equivalent electrical and thermal performance to soft solder.
Clip-Based Power Packages • Clip-based power packaging is growing in popularity for medium power packages. Clip technology offers improved electrical and thermal performance in a low-cost package. – Dpack – Power SO – QFN
Source: NXP
Source: Prismark
Source: Prismark
TLPS technology has ability to have high reliability performance to a wide range of surfaces found in clip-base power packages: - Ag plated die and leadframe - PPF plated leadframe - Bare copper leadframe and clip - Nickel plated bondpads
TLPS die attach vs. PbSn Solder: Clip Packages: Customer Feedback
Package #1
Rdson (mohm)
T0 % Delta Rdson (mohm)
AVG
Delta vs Solder
PbSn Control
4.3
0
TLPS Split #1
4.3
TLPS Split #2
4.4
Package #2
Rdson (mohm)
% Delta Rdson (mohm)
AVG
Delta vs Solder
PbSn Control
1.8
0
+1.5%
TLPS Split #1
1.9
+2.0%
+1.1%
TLPS Split #2
1.8
+0.2%
TLPS technology is equivalent to solder’s electrical performance and has a broad process window to meet customer factory process requirements.
Reliability Testing: Clip Packages – Baseline (Time 0) Rdson: • Within 2% of High-Pb Control – HTS (150C) 168 Hour: • Complete w/ no Rdson degradation – MSL2: No Failures – Autoclave 144 Hours: No failures – Thermal Characterization: • Comparable to High-Pb Control – Post 1500 Temperature Cycles • (-65/150C): No Failures • (-55/125C): No Failures • (-40/125C): No Failures
System Level Performance Assessment
Solder Control Max: 81.3°C
Ormet Max: 79.7°C
No observed difference in device electrical response, power loss or thermal performance
Cross Section • The metal network is thermally stable to over 400C • The liquid Sn bonds to the metalized die backside and leadframe • The strong metallurgical bonds at the leadframe and die interfaces enable stable RDson performance post MSL and TCT Sn-Cu
Metallurgical bonds at interfaces
Black Regions are Epoxy Resin
TLPS’s sintered metal network will not re-melt below 400C
3
System-in-Package Solder Replacement
Challenges with SIP Modules
Source: Linear Technologies website
SIP modules utilizing copper leadframes or BT substrate can have a range of issues: 1. Yield: Solders often have significant voiding underneath QFN packages 2. Reliability: Solders inside the SIP remelt during surface mount reflow and may extrude from the package 3. Cost: • Solder hierarchy drives narrow process windows • Variable component height drives thick (expensive) mold cap 4. Rework: Package rework difficult unless mold compound is used 5. Green: High temperature solder compositions can contain hazardous materials
TLPS for SiP Benefits for SIP: 1. Paste will not flow or splash during assembly, enabling higher component density 2. TLPS Materials will not re-melt during subsequent reflows, reducing potential for solder extrusion during surface mount assembly 3. Pastes can be used for both die attach and passive attach, simplifying assembly processes Solder - Inside SIP - Joins SIP to PCB
System-in-Package Component
PCB
Pb-free TLPS materials can be used to attach die and/or components in leadframe and substrate-based modules
TLPS Paste Before and After Reflow
TLPS materials do not slump/flow like solder during reflow. Cu-Sn TLPS materials change from copper to gray color during sintering process.
TLPS Solder Replacement Materials can be used without Solder Mask for Small Components Fillets are similar to conductive adhesive rather than solder
Cap Size: 0402 and 0603
Shear Strength Comparison
TLPS shear strength comparable to SAC305 after 1000 cycles -65C to 150C
