Fine Pitch Interconnect Rework for Lead-Free Flip Chip Packages
Notice bibliographique
Résumé
Multiple device configurations, especially in 2.5D or 3D systems, are intimately tied to the successful implementation of very fine pitch, flip chip interconnection in order to optimize their potential for higher performance and smaller form factor. At the same time, such pitch reduction and increased I/O count create greater challenges to the interconnection process and its resulting reliability, imposing a greater focus on the overall process definition for these systems in a package, including the need to develop a suitable process to remove and replace individual defective device, more commonly known as device rework. However, the aforementioned trends in interconnect dimensions present significant challenges to the rework process as well, rendering conventional approaches difficult if not practically obsolete. It was therefore the goal of this study to investigate a localized thermal head separation approach for the rework of very fine pitch 2.5D/3D configurations that would obviate the need for solder redress/replenishment while preserving the overall integrity of both reworked and adjacent device. Adapting standard commercial thermo-compression bonding (TCB) tools, heating and separation parameters were investigated for removing an 11.1mm × 8.7mm device comprising Cu pillar/Pb-free solder interconnects from its underlying active TSV interposer assembled onto an organic laminate substrate. Initial joining parameters of the device (TCB versus furnace reflow bonding), peak temperature and holding times were varied to understand the sensitivity of the thermal separation process. Separation quality was characterized from the perspectives of fracture mode, separation metallurgy and residual pad height distribution. Results demonstrated that, while optimum conditions could be obtained for both shear and tensile solder separation approaches, the latter afforded a greater parameter window to avert undesirable separation interfaces (TiW-passivation) without introducing a solder dragging effect. However, should the issues of TiW-die passivation separation be resolved using functional die or thermal mismatch mitigation, the shear approach, as supported by Instron strength measurements, could be favorable to separate the interconnects at a lower force than tensile separation at temperatures below liquidus, thus avoiding the solder dragging issue. Height distribution measurements, while limited by the contact profilometer means combined with the uneven solder distribution on individual pads, appeared sufficiently consistent, at optimized separation parameters, to allow die replacement without the need for solder replenishment at the die site. While preliminary die replacement tests to validate this hypothesis showed a greater joining sensitivity of the reworked sites compared to non-reworked sites, means to improve oxide reduction and alignment were shown to improve and even correct joining issues, paving the way for future optimization of this very fine pitch, flip chip rework method.
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Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,001 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,002 | 0,001 |
| Intégrité de la recherche | 0,001 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».