{"title":"Effects of different air gaps of underfill encapsulant on multi-stack printed circuit board","authors":"","doi":"10.1016/j.microrel.2024.115533","DOIUrl":null,"url":null,"abstract":"<div><div>This paper studies the effect of different air gaps on multi-stack printed circuit board (PCB) using finite volume method (FVM). Air gaps of 150 mm<sup>2</sup> and 450 mm<sup>2</sup> were introduced to investigate their influence on flow parameters such as filling time, pressure distribution, and void formation during the capillary underfill encapsulation process. It was found that increasing the air gap size improved the filling time by 10 %, though it also doubled the pressure, which helps reduce void formation but requires careful control to prevent encapsulant overflow. Throughout the study, an L-type dispensing method was applied on a perimeter type multi-stack BGA with wall type barrier added on the sides of the multi-stack PCB to prevent encapsulant. This new wall type barrier henceforth requires comprehensive study on the size of the air gaps to ensure crucial flow parameters such as void formation, filling time, pressure distribution and flow front pattern are optimized. Two air gap sizes given as 150 mm<sup>2</sup> and 450 mm<sup>2</sup> are used in this study. Moreover, the fluid flow patterns from both studies are investigated to determine the problem of racing effect and void formation. Based on the findings, it was found that 10 % improvement in the filling time can be made by using a bigger air gap of 450 mm<sup>2</sup>. However, with bigger air gap, the pressure increases two-fold which can be good in reducing the void formation though the trade-off can be on the risk of excessive overflow of encapsulant.</div></div>","PeriodicalId":51131,"journal":{"name":"Microelectronics Reliability","volume":null,"pages":null},"PeriodicalIF":1.6000,"publicationDate":"2024-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Microelectronics Reliability","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0026271424002130","RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"ENGINEERING, ELECTRICAL & ELECTRONIC","Score":null,"Total":0}
引用次数: 0
Abstract
This paper studies the effect of different air gaps on multi-stack printed circuit board (PCB) using finite volume method (FVM). Air gaps of 150 mm2 and 450 mm2 were introduced to investigate their influence on flow parameters such as filling time, pressure distribution, and void formation during the capillary underfill encapsulation process. It was found that increasing the air gap size improved the filling time by 10 %, though it also doubled the pressure, which helps reduce void formation but requires careful control to prevent encapsulant overflow. Throughout the study, an L-type dispensing method was applied on a perimeter type multi-stack BGA with wall type barrier added on the sides of the multi-stack PCB to prevent encapsulant. This new wall type barrier henceforth requires comprehensive study on the size of the air gaps to ensure crucial flow parameters such as void formation, filling time, pressure distribution and flow front pattern are optimized. Two air gap sizes given as 150 mm2 and 450 mm2 are used in this study. Moreover, the fluid flow patterns from both studies are investigated to determine the problem of racing effect and void formation. Based on the findings, it was found that 10 % improvement in the filling time can be made by using a bigger air gap of 450 mm2. However, with bigger air gap, the pressure increases two-fold which can be good in reducing the void formation though the trade-off can be on the risk of excessive overflow of encapsulant.
期刊介绍:
Microelectronics Reliability, is dedicated to disseminating the latest research results and related information on the reliability of microelectronic devices, circuits and systems, from materials, process and manufacturing, to design, testing and operation. The coverage of the journal includes the following topics: measurement, understanding and analysis; evaluation and prediction; modelling and simulation; methodologies and mitigation. Papers which combine reliability with other important areas of microelectronics engineering, such as design, fabrication, integration, testing, and field operation will also be welcome, and practical papers reporting case studies in the field and specific application domains are particularly encouraged.
Most accepted papers will be published as Research Papers, describing significant advances and completed work. Papers reviewing important developing topics of general interest may be accepted for publication as Review Papers. Urgent communications of a more preliminary nature and short reports on completed practical work of current interest may be considered for publication as Research Notes. All contributions are subject to peer review by leading experts in the field.