Design and Process Effects on the Reliability of 1.0 mm Pitch CBGA
Bibliographic record
Abstract
ABSTRACT The ceramic ball grid array (CBGA) package is used today in a wide range of applications, because of its many advantages: high interconnection density; compatibility with standard surface mount technology (SMT) assembly techniques; excellent thermal and electrical performance; and high interconnectivity. Today's CBGA applications include memory, logic, and microprocessors and are found in computer systems ranging from desktop to mainframe, with highest usage in work station and server applications. Advances in printed circuit board technology and card assembly processing have enabled the implementation of the finer pitch CBGA packages that are in demand to meet the needs of increasing interconnect density. CBGA packages with a 1.0 mm pitch ball array have been recently qualified and are now shipping to several customers for a variety of applications. The most common sizes and ball counts are 25 mm with 552 I/O, 25×32.5 mm with 720 I/O and 32.5 mm with 937 I/O. Initial qualification activities focused on the basic groundrules, dimensions and processing - such as the printed circuit board pad size, the substrate pad diameter, the solder ball diameter and the card assembly solder volume. As the technology is implemented and begins production, it becomes important to understand additional factors that can effect the solder joint thermal fatigue life. This paper will discuss the evaluation of many design and process factors that can effect the interconnect reliability. Design factors investigated include the thickness of the ceramic substrate, the depopulation of corner ball locations, and the option of a Direct Lid Attach (DLA) lid. Process factors that have continued to be investigated include the card assembly solder volume, the card assembly reflow profile, and the card assembly rework process
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".