Application Note Application Note AN102
Application Note AN102 Balling and Reballing with Plastic Core Solder Balls Introduction Plastic Core Solder Balls (PCSB) provide a method of assuring stand-off off height heigh between an IC package and a substrate or PCB and can deliver other benefits. Utilising standard Retronix ball attachment processes, PCSBs provide a Pb free method of assuring the required stand-off. stand Applications for PCSBs Stand-off off height assurance for mechanical integrity. Prevention of excessive displacement of solder due to package weight. Pb free alternative to High Melting Point (HMP) spheres. spheres Improved mechanical integrity integrity where there is significant thermal expansion mismatch between the IC package and the PCB or substrate. Package on Package devices. RF/Microwave modules – ensures consistent path lengths and inductances. induct LTCC and Aluminium Nitride modules with spheres as connections. WLCSP ICs – larger die size devices may not need underfill for mechanical mechan integrity. PCSB Construction
PCSBs have an embedded polymer core with Cu and Ni barrier layers. Following reflow and through life the core maintains its mechanical integrity. Figure 1 shows the construction of the PCSB.
Fig 1. PCSB Construction
During reflow using SAC305 solder paste, the Ni barrier and the doped Ni in the PCSB are incorporated into the solder forming a fine IMC around both the Cu pad of the PCB (or IC package) and the Cu layer of the PCSB. Figure 3 shows the intermetallic formation.
Fig 2. Intermetallic Formation of Ni Doped PCSB AN102 Retronix onix Plastic Core Solder Balls
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JMc Jan ‘13
Application Note AN102
Fig 3.. Comparison of PCSB to Standard Spheres The difference in stand-off off height achieved between PCSBs and standard spheres is demonstrated in the example in Figure 3. Reliability
Max Min Avg
Failure Strength (gf) 354 336 296 251 320 292 PCSB SAC305
Shear Test results demonstrate good results, in fact even slightly better than SAC305 spheres.
Table 1. Shear Tests (5 times reflow) re
Fig 4. Shear Test Setup
Drop tests to JESD 22-B111 B111 and temperature cycling over -40°C to +125°C also demonstrate very ery good performance (further data available on request).
AN102 Retronix onix Plastic Core Solder Balls
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JMc Jan ‘13
Application Note AN102
Fig 5. Retronix Assembled Packages (Plastic BGA and Ceramic LCC) Summary Retronix has the capability to provide PCSB balling and reballing, providing benefits in a wide range of applications and markets.
AN102 Retronix onix Plastic Core Solder Balls
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JMc Jan ‘13
PCSBs have an embedded polymer core with Cu and Ni barrier layers. Following reflow and through life the core maintains its mechanical integrity. Figure 1 shows the construction of the PCSB.
Fig 1. PCSB Construction
During reflow using SAC305 solder paste, the Ni barrier and the doped Ni in the PCSB are incorporated into the solder forming a fine IMC around both the Cu pad of the PCB (or IC package) and the Cu layer of the PCSB. Figure 3 shows the intermetallic formation.
Fig 2. Intermetallic Formation of Ni Doped PCSB AN102 Retronix onix Plastic Core Solder Balls
1
JMc Jan ‘13
Application Note AN102
Fig 3.. Comparison of PCSB to Standard Spheres The difference in stand-off off height achieved between PCSBs and standard spheres is demonstrated in the example in Figure 3. Reliability
Max Min Avg
Failure Strength (gf) 354 336 296 251 320 292 PCSB SAC305
Shear Test results demonstrate good results, in fact even slightly better than SAC305 spheres.
Table 1. Shear Tests (5 times reflow) re
Fig 4. Shear Test Setup
Drop tests to JESD 22-B111 B111 and temperature cycling over -40°C to +125°C also demonstrate very ery good performance (further data available on request).
AN102 Retronix onix Plastic Core Solder Balls
2
JMc Jan ‘13
Application Note AN102
Fig 5. Retronix Assembled Packages (Plastic BGA and Ceramic LCC) Summary Retronix has the capability to provide PCSB balling and reballing, providing benefits in a wide range of applications and markets.
AN102 Retronix onix Plastic Core Solder Balls
3
JMc Jan ‘13
