Underfill optimization under accelerated temperature cycling and drop-impact loading for stacked packages using finite element modeling

Tian

2012

Jpn. J. Appl. Phys.

In this paper, we present the results of temperature cycling test for full and partial capillary flow underfilled lead-free chip scale packages (CSPs), the tests were carried out on the basis of JEDEC standard. Two kinds of representative fast cure and reworkable underfill materials are used in this study, and CSPs without underfills were also tested for comparison. The test results show that the two underfill materials reduce the thermomechanical fatigue performance of CSP assemblies. The underfill with high T g and storage modulus yielded better performance; indeed, the coefficient of thermal expansion (CTE) is also very critical to the thermomechanical fatigue performance, but its effects is not so obvious in this study owing to the similar CTEs of the underfills used. In addition, the negative effect of a partial underfill pattern is smaller than that of a full underfill pattern. Failure analysis shows that the dominant failure mode observed is solder cracking near the package and/or printed circuit board pads.

Section: Test Results and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thermomechanical Fatigue Performance of Lead-Free Chip Scale Package Assemblies with Fast Cure and Reworkable Capillary Flow Underfills

Tian

2012

Jpn. J. Appl. Phys.

“…In their numerical parametric study, they found that the maximum z-plastic strain of the package corner solder joint increases with the modulus of the bonding materials, but the CL of the critical solder joint (package corner solder joint) reaches its peak at 0.5 times (0.4 GPa) the baseline modulus. Schneck and Johnson 31) built an array of accelerated temperature cycling finite element simulations using ANSYSÔ determine the optimum underfill for a stacked chip scale package. The modulus was varied from zero (no underfill) to 15 GPa and the CTE was varied from 5 to 75 ppm/ C. The ATC conditions were 0-100 C; with 10 min ramp period and 5 min dwell period.…”

Section: Effects Of Dispensing Patterns On the Thermal Cyclingmentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8] Later, FCFU was also used in array-based packages (ABPs) at the board level to improve the reliability of such packages under mechanical shock, vibration, bend, torsion and shear during assembly and shipment. [9][10][11][12][13][14][15][16] However, the reliability enhancement gain from underfilling the full ABP region comes at the expense of higher manufacturing cost, due to the slow rate of capillary flow of underfill. This is especially true for large packages such as 30 Â 30 mm 2 packages or larger.…”

Section: Introductionmentioning

confidence: 99%

Board-Level Solder Joint Reliability of Edge- and Corner-Bonded Lead-Free Chip Scale Package Assemblies Subjected to Thermal Cycling

Tian

2012

Jpn. J. Appl. Phys.

In this paper, we present the results of thermal cycling test for edge- and corner-bonded lead-free chip scale packages (CSPs), which was carried out on the basis of the IPC-9701 test standard. Six materials were used in this study: four edge-bond adhesives and two corner-bond adhesives. These adhesives were compared with CSPs with full capillary flow underfill (FCFU) and without adhesives. The thermal cycling test results show that corner-bond adhesive has comparable solder joint reliability performance with CSP without adhesive, and is better than edge-bond adhesive, followed by CSPs with FCFU. In addition, the adhesives with a low coefficient of thermal expansion, a high glass transition temperature and a intermediate storage modulus yielded good performance. Results of detailed failure analysis indicate that the dominant failure mode is solder bulk fatigue cracking near package and/or printed circuit board (PCB) pads, and that the location of critical solder joints change from die edges to package corners with the introduction of adhesives.

“…In order to protect and prolong the life of flip chip interconnects, the underfill was introduced and became an essential component especially for organic substrates (or chip carriers). Later, underfill was also used in ball grid array (BGA) packages at the board level in order to improve the reliability of the packages under mechanical shock, vibration, bend, torsion and shear during assembly and shipment [1][2][3][4][5][6][7][8]. In many BGA applications, however, underfilling the full BGA region provides far more strength and reliability than needed at the expense of high cost in manufacturing especially for large-sized packages (30 x 30 mm and larger), due to the slow rate of capillary flow of underfill.…”

Section: Introductionmentioning

confidence: 99%

Thermal cycling reliability of lead-free package stackable very thin fine pitch ball grid array assemblies with reworkable edge and corner bond adhesives

2011 12th International Conference on Electronic Packaging Technology and High Density Packaging

2011

This paper presents the thermal cycling test results for edge and corner bonded 0.5 mm pitch lead-free package stackable very thin fine pitch ball grid arrays (PSvfBGAs) as package-on-package (PoP) bottom packages on a quasistandard JEDEC thermal cycling test board. Thermal cycling tests were carried out based on the JEDEC JESD22-A104C standard, -40 ~ 125°C temperature range with 32 minutes/cycle test condition was applied, and hold times in each extreme temperature were 10 minutes. The daisy chain resistance of each PSvfBGA was measured by an event detector and a 1000 Q rise (or more) from initial resistance was considered as the failure criterion. Three materials used in this study were a UV-cured acrylic edge bond adhesive, a thermal-cured epoxy edge bond adhesive and a thermal-cured epoxy corner bond adhesive, and PSvfBGAs without bonding were also tested for comparison. Statistics of the number of cycles-to-failure for the 45 components of each test group are reported. The test results show that the characteristic lives of PSvfBGAs with edge bond acrylic, edge bond epoxy and corner bond epoxy are respectively about 0.6, 0.9 and 1.3 times of the PSvfBGAs without bonding. The corner bond epoxy with lowest CTE, highest storage modulus and smallest adhesive volume yielded best performance. Because it can slow down the CTE mismatch and reduce effective action area of interactive forces between the adhesive, BT substrate and PCB during thermal cycling test. So if we want to improve the thermal cycling reliability of PSvfBGA with adhesives, the thermal-mechanical material properties and dispending patterns of adhesives should be thoroughly considered. Failure analysis was performed using dye-andpry, cross section scanning electron microscope (SEM) and energy dispersive X-ray (EDX) methods. The common failure mode observed is solder cracking near package and/or PCB pads.