Article : [PAP462]

Titre : D. Wojciechowski, Moses Chan, Fabrizio Martone, Lead-free plastic area array BGAs and polymer stud grid arraysTM package reliability, Microelectronics Reliability, Volume 41, Issue 11, November 2001, pp. 1829-1839.

Cité dans :[REVUE257] Elsevier Science, Microelectronics Reliability, Volume 41, Issue 11, Pages 1737-1913, November 2001.
Cité dans :[PAP360]

Adresse : CS2, Hermesstraat 2A, 1930 Zaventem, Belgium
Source : Microelectronics Reliability,
Volume : 41
Issue : 11
Date : November 2001
Pages : 1829 - 1839
Info : Received 27 November 2000; revised 30 March 2001. Available online 2 October 2001.
Lien : private/Wojciechowski.pdf - 838 Ko, 11 page

Abstract :
Many packaging and original equipment manufacturers (OEMs) have initiated a
program of introducing lead-free electronics. Although lead usage in the
packaging industry is relatively small, major efforts are ensuring to eliminate
lead usage. In this context, we manufactured and qualified two "green" package
solutions: lead-free low-profile fine pitch ball grid array (LFBGA) and polymer
stud grid arrays (PSGATM) area array packages.
The primary source of lead in BGA is in the solder balls. Lead-free solder
alloys are readily available, although there is no universal drop-in replacement
identified so far for plastic BGAs. One of the most promising alloys for this
purpose appears to be the eutectic Sn95.5Ag4Cu0.5, although it involves higher
processing temperature. Based on a design of experiment (DOE), the best reflow
profile has been determined and used. A lead-free 8×8 mm2 LFBGA has been
manufactured without other process or equipment changes, and has been qualified
for JEDEC moisture level 3, with 245°C reflow simulations, and standard 1st
level package reliability tests.
An alternative to lead-free plastic BGA is the PSGATM. The PSGATM package
consists of a polymer injection-molded 3D body with a location for chip mounting
and polymer studs. The metallized studs, which are by nature lead-free, replace
the solder balls within the BGA package. Moisture conditioning and reliability
analysis was performed on 8×8 mm2 PSGATM. The package passed JEDEC moisture
conditioning level 3 as well as standard reliability tests.

Article Outline
1. Introduction
2. Area array packages
2.1. Ball grid array
2.2. Polymer stud grid array
3. Lead-free materials
3.1. Lead-free BGA materials
3.1.1. Solder materials
3.1.2. Fluxes
3.1.3. Laminate BGA substrate
3.2. PSGATM body
3.3. Common materials
4. Lead-free assembly process
4.1. Lead-free BGA assembly
4.2. PSGATM assembly
5. Area array package reliability
5.1. Moisture sensitivity effects and reliability qualifications
5.2. Lead-free BGA package reliability results
5.3. PSGATM package reliability results
6. Conclusion
References

(31K)
Fig. 1. BGA and PSGATM area array packages process flowcharts.

(10K)
Fig. 2. BGA package perspective side view.

(25K)
Fig. 3. Laser-structured I/Os bottom view and close view of studs' geometry.

(13K)
Fig. 4. Cavity up OTE PSGATM.

(19K)
Fig. 5. Cavity up microvia PSGATM (package and body).

(25K)
Fig. 6. Assembled BGA laminates (strip configuration).

(25K)
Fig. 7. Microvia PSGATM cross-section (encapsulated via globtop).

(8K)
Fig. 8. Ball reflow soldering profiles for standard eutectic Sn63Pb37 versus
lead-free Sn95.5Ag4Cu0.5 balls.

(38K)
Fig. 9. Sn63Pb37 (top) and Sn95.5Ag4Cu0.5 (bottom) balls morphology and
metallurgical phases.

Table 1. Plastic BGA package families (<1K)

Table 2. Typical lead content in BGAs (<1K)

Table 3. Lead-free solder alloy with a melting temperature equivalent to the
Sn63Pb37 (183°C) (<1K)

Table 4. BT-resin and LCP properties (<1K)

Table 5. JEDEC moisture sensitivity levels (<1K)

Table 6. BGA reliability for MSLC level 3 (<1K)

Table 7. Lead-free BGA package reliability results (<1K)

Table 8. PSGATM package reliability results (<1K)

References
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2. Draft proposals for a European parliament and council directive on waste
electrical and electronic equipment (WEEE), amending Directive 76/769/EEC, 1999
& 2000, www.lead-free.org.
3. Richards BP, Nimmo K, et al. An analysis of the current status of lead-free
soldering. Report by National Physical Laboratory and ITRI Ltd., 1999,
www.lead-free.org.
4. Elenius P, Yeh S. Lead free solder for flip chip and chip scale packaging
(CSP) applications. Proc IPC Works, 1999. p. S-03-2-1¯6.
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and non-destructive control of electronic component: BGA/CSP/lead-free process",
France, 1999.
6. Wojciechowski D, Truzzi C. Impact on BGAs, process and equipments of
lead-free soldering. Proc Int Microelectron Packag Soc (IMAPS Europe, Prague,
Czech Republic), June 2000. p. 308¯13.
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9. European patent application no. P 44 34 086.9.
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11. Vandevelde B, Beyne E. The polymer stud grid array (PSGATM) package: a
thermal fatigue reliability study, IMAPS Nordic, 36th Annual Conference,
Kalastajatorppa, Helsinki, Finland, 19¯22 September, 1999.
12. Vandevelde B, Beyne E. Effect on thermal fatigue reliability of decreasing
the pitch of PSGA packages from 0.8 to 0.3 mm. Area Array Packaging Workshop,
Berlin, Germany, 15¯17 November, 1999.
13. Vandevelde B, Driessen E, Chandrasekhar A, Beyne E, Reliability assessment
for the polymer stud grid array (PSGATM) package, IMAPS Nordic, 37th Annual
Conference, Helsingor, Denmark, 11¯13 September, 2000.
14. Massiot M, Wojciechowski D, Truzzi C, Beyne E. Lead-free solder BGAs and
polymer stud grid arrays. Proc Int Conf Electron Goes Green 2000+, vol. 1.
Berlin, Germany, September 2000. p. 93¯7.
15. Reid FH, Goldie W. Gold plating technology. San Diego: Electrochemical
Publications Ayr; 1974. p. 225¯46.
16. Khan M, et al. Effect of high thermal stability mold material on the
gold¯aluminium bond reliability in epoxy encapsulated VLSI devices. IEEE Int
Reliab Phys Symp, 1988. p. 40¯7.
17. Tay AAO, Lin TY. The impact of moisture diffusion during solder reflow on
package reliability. Proc IEEE Electron Comp Technol Conf, 1999. p. 830¯6.
18. Solberg V. Lead-free soldering for CSP ¯ the impact of higher temperature
SMT assembly processing. Proc IMAPS, Boston, Massachusetts, 2000. p. 611¯6.
19. Prasad S, Carson F, Kim GS, Lee JS, Seong TS, Kim YS. Reliability of
lead-free BGA packages. Proc IMAPS, Boston, Massachusetts, 2000. p. 722¯6.

1 Since May 2001, DW joined Alcatel Microelectronics as Senior Packaging
Engineer, Westering 15, 9700 Oudenaarde, Belgium. Tel.: +32-55-332211; fax:
+32-55-318112.
Corresponding author. Address: Chaussée d'Hondzocht 103A, 1480 Tubize, Belgium;
email: d.wojciechowski@mie.alcatel.be; email: d.wojciechowski@tiscalinet.be;
email: http://www.cs2.be

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Microelectronics Reliability
Volume 41, Issue 11
November 2001
Pages 1829-1839

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