Lead-Free Card Assembly and Rework for Column Grid Arrays
Bibliographic record
Abstract
ABSTRACT IBM introduced copper column grid array (CuCGA) interconnect as the lead-free replacement for the lead-tin solder column on the ceramic column grid array (CCGA) (Figure 1). Like CCGA, CuCGA offers a high reliability packaging solution, enabling the use of ceramic chip carriers with excellent electrical and thermal performance. Figure 1: Copper column grid array (left) and CLASP CCGA (right). The move to eliminate lead in microelectronic packaging increases the complexity of processing large body size, high I/O packages. The development of manufacturable card assembly and rework processes in concert with the development of a new package interconnect structure is key to technology acceptance. Copper column interconnect (CuCGA) has been designed to meet the requirements of manufacturability, reliability, and electrical performance. Optimization of the structure for manufacturability focused on the robustness of the column during manufacturing handling and the ease of card assembly processing. The resulting card-side solder joint is key to the reliability of the interconnect. The interconnect geometry also influences electrical performance [1]. Evaluating these competing factors determined the final column design [2]. This paper focuses on the development and reliability evaluation of the CuCGA card assembly and rework processes. The goal of the process development was to adapt the successful SMT assembly process for CCGA to the developing standards for lead-free SMT processing. Successful integration of the assembly processing of the CuCGA into the developing tin-silver-copper (SnAgCu, or SAC) card assembly process posed challenges in the areas of placement, reflow, and rework. The optimization of these processes, and the proof of successful results demonstrated by reliability evaluations, will be discussed.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".