C4NP: Lead-Free and Low Cost Solder Bumping Technology for Flip Chip and Wlcsp
Bibliographic record
Abstract
ABSTRACT Today, various solder bumping technologies are being used in volume production. These include electroplating, solder paste printing, evaporation and the direct attach of preformed solder spheres. 1 However, all these established technologies have important limitations for fine pitch bumping with lead-free alloys: Evaporation is too costly in general, solder paste printing often does not provide the desired bump stand-off height when it comes to fine-pitch bumping, electroplating is found to be expensive and difficult to control for lead-free alloys and preformed solder spheres are only applicable for a pitch down to approximately 500 microns. These challenges in the transition to lead-free solder bumping has led the European Union to grant exemptions until 2010 from the ban of lead in certain solder bumping applications. However, the pressure to move to lead-free continues for the entire industry. C4NP (C4-New Process) is a novel solder bumping technology developed by IBM and commercialized by Suss MicroTec. C4NP addresses the limitations of existing bumping technologies by enabling low-cost, fine pitch bumping using a variety of lead-free solder alloys. C4NP is a solder transfer technology where molten solder is injected into pre-fabricated and reusable glass templates (molds). Mold and wafer are brought into close proximity and solder bumps are transferred onto the entire 300mm (or smaller) wafer in a single process step. C4NP technology is capable of fine pitch bumping while offering the same alloy selection flexibility as solder paste printing. The simplicity of the C4NP process makes it a low cost solution for both, fine-pitch FC in package as well as WLCSP bumping applications. This paper reviews the current status of the first C4NP lines installed at semiconductor manufacturers. It discusses the relevant process equipment technology and a manufacturing cost model. Last but not least, the presentation includes manufacturing data provided by IBM’s packaging operation at the Hudson Valley Research Park in East Fishkill, NY.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".