October, 2024
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Local PCB Warpage with AI and Large Area BGAs... Continued from previous page
measure samples during an in-situ reflow cycle. Other techniques lack either the
speed, data density, or measurement resolution in measuring large PCBs. Akrometrix tools use custom built ovens to recreate the thermal condi- tions and profile timing seen by these devices in production and utilize the shadow Moiré technique to capture sample warpage at key points in time through the reflow process. With warpage over temperature of
both BGA and PCB local area, manu- facturers can compare against industry standards for surface mount devices. They could further make some assumptions around criteria for the PCB based on those industry stan- dards. Yet, this approach has two key flaws. First, the assumption of 20 percent warpage on the PCB side is not expected to hold up for larger BGA attach areas. Second, considering the sur-
faces separately ignores how the shapes of the surface match. Consider two surfaces that have a dome-like shape around solder liq- uidus temperatures and follow similar shapes as they cool. Even if both have significant shape, if their shape is the same, likely warpage will not be an issue with a quality surface mount attach- ment. Now consider shapes of the same magnitude but the top shape is like a bowl. In this scenario, opens or at least stretched joints at the package corners become a real concern.
Interface Analysis The Interface Analysis soft-
ware is used to visualize, quantify, and report on the gaps seen between component and PCB com- paring across like temperatures for each sample. It provides criti- cal gauges to quantify gaps between attaching surfaces, including max and average gap. Furthermore, the software
can provide statistical information across multiple sample groups for understanding trends and check- ing quality for surface mount devices. The technology is auto- mated to use metadata contained specifically in Akrometrix meas- urement files to orient the meas- ured surfaces as they would be during actual assembly. Comparing surfaces through
the Interface Analysis software allows manufacturers to make early design decisions, compare different material choices and suppliers, increasing product yield and relia- bility. The IA comparison can even be done when data is captured in separate locations, such as a PCB fabricator and a semiconductor assembly and test site measuring PCB and BGA separately in outgo- ing quality control. Thermal warpage metrology
is already a common practice throughout the microelectronics industry and in particular for
See at SMTAI, Booth 2929 Interface analysis with Pass/Warn/Fail.
Page 57
advanced packaging. With the grow- ing need for larger packages on larger server boards, the need for large area and accurate thermal warpage metrol- ogy is similarly growing. Here Interface Analysis and shadow Moire are particularly suited to address the emerging challenges that come with quickly increasing package sizes. Thus, expectations are that the indus- try will increasingly need IA for AI. Contact: Akrometrix, 2700 NE
Expressway, Building B, Suite 500, Atlanta, GA 30345 % 404-282-8524 E-mail:
nhubble@akrometrix.com Web:
www.akrometrix.com r
See at SMTAI, Booth 2736
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