Taking a close look at voids in BGA solder balls

Taking a close look at voids in BGA solder balls:

Researchers are questioning the impact of voids in BGA solder balls. They may not cause defects, which may prompt a revision of standards that set defect levels for voids.

 
January 21, 2013

By Terry Costlow, IPC online editor

Manufacturing processes evolve as clever employees find ways to eliminate defects. Ball grid arrays (BGAs) are a case in point: Some defects like solder ball voids were once considered a major problem, but some researchers say they’re no longer an issue.

As ball sizes and spacing have shrunk and processes have improved, voids in solder balls may no longer be a problem. That’s a marked change from years past, and one that may call for a standard revision.

For years, J-STD-001, Requirements for Soldered Electrical and Electronic Assemblies, and IPC-A-610, Acceptability of Electronic Assemblies, had very specific guidelines for BGA solder balls. The standards say BGAs are defective when voids account for more than 25 percent of an X-ray image area. But many say that as more industry investigations have been completed, that criterion is no longer valid.

When those standards were written, lead spacings were around 1.27 mm and ball diameters were around 30 mils. Now spacings are 0.5-0.8 mm and ball sizes are 10-20 mils.

“At those dimensions, if you get a void in the solder ball, there is a high probability it’s going to be greater than 25 percent of the X-ray image area,” said Dave Hillman, principal materials and process engineer at Rockwell Collins.

Some say that voids degrade the solder ball joint, while others have done research showing that voids have little impact on reliability. Solder joints with voids of any size likely have other problems that would cause failure.

“There may be some confounding issues in test methodologies. When you’re seeing a wide diversity in industry BGA void test results, it can mean test vehicles, test parameters or testing condition setups are having an influence on the test results in contrast to other industry tests,” Hillman said.

Hillman will provide more detail at IPC APEX EXPO® in San Diego February 19-21. The title of his Wednesday morning technical conference session lays out his views on the topic: “The Last Will and Testaments of Tin/Lead and Lead-Free BGA Voids.”

Hillman, who has worked closely with Hewlett Packard’s Chris Troxel and Linda Woody of Lockheed Martin Missile and Fire Control on this issue, feels that it’s time to alter IPC standards to eliminate the defect criteria on voids.

“If all of the industry data is reviewed and BGA voids are determined to not be a defect, voids shouldn’t be in the standards as a defect,” Hillman said.

Instead of focusing on defects, manufacturers should tweak their processes when they see an increase of void occurrence or size. Changes in the appearance, size or shape of solder contacts often suggest that the process is beginning to go out of range. Monitoring the process can be more effective than testing for defects.

“J-STD-001E and IPC-A-610 use process control methodologies/protocols in a number of solder process areas rather than 100 percent visual inspection,” Hillman said.

While noting that there are many benefits to inspection with the broad range of tools now available, Hillman commented that there can be cases where visual inspections are no longer beneficial. That can be the case with solder voids, which aren’t visible without advanced inspection equipment.

“One of the negative aspects of X-ray inspection is that it lets you see things you couldn’t see before. A process engineer now needs to make a determination if the things being seen are a problem or an observation. Voids in BGAs are the poster child for this issue,” Hillman said. “You get more immediate benefits by establishing consistent solder processes than scanning for voids after the fact.”

Hillman feels that it’s important to update standards as more knowledge is gained. When J-STD-001 and IPC-A-610 were written, solder voids were thought to be a problem. But as technology has advanced and new test data is accumulated, researchers have found that they’re something of a red herring.

“A willingness to change workmanship criteria shows the flexibility of the industry and IPC,” Hillman said.

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RoHS the world over

Through the draft Regulation on the Declaration of Conformity for Pollution Control in Electrical and Electronic Product Enterprises of 18 July 2012 (公开征集《电子电气产品污染控制企业符合性声明规范》意见), China is taking one-step further action on the implementation of advanced RoHS control system. Amongst others, the draft Regulation of 18 July 2012 would provide all EEE producers and importers with a harmonized method of proofs and declaration on their conformance with voluntary and mandatory RoHS scheme in China.

Israel finally adopted the Environmental Treatment of Electrical and Electronic Equipment Law 2012 (חוק לטיפול סביבתי בציוד חשמלי ואלקטרוני ובסוללות, התשע"ב-2012) which is combination of the EU Directive on waste electrical and electronic equipment (WEEE2 recast) 2012/19/EU of 4 July 2012 and Directive 2006/66/EC on waste batteries and accumulators. The Law will require manufacturers and importers of electrical and electronic equipment (including batteries) to meet take-back and recycling targets as well as reporting and record keeping obligations as from 1 January 2014. EU WEEE Recast Directive 2012/19/EU of 4 July 2012 will extend WEEE requirements to all EEE placed on the EU market as from 15 August 2018.

Peru Supreme Decree No. 001-2012-MINAM approving the Regulation on the Management of Waste Electric and Electronic Equipment (Decreto Supremo No. 001-2012-MINAM que aprueba el Reglamento Nacional para la Gestión y Manejo de los Residuos de Aparatos Eléctricos y Electrónicos) starts requiring producers, importers, and/or distributor of electric and electronic equipment to have or enroll in a WEEE management system as from 28 June 2012. The draft European Commission Regulation of July 2012 implementing Directive 2009/125/EC of the European Parliament and of the Council with regard to ecodesign requirements for computers and computer servers is another big issue for electronics companies and may potentially impact:
- desktop computers;
- integrated desktop computers;
- notebook computers;
- desktop thin clients;
- workstations and mobile workstations; and
- small-scale servers and computer servers.

• [Cyprus] Recovery and recycling obligations of packaging extended to more companies
• [EU] Directive on energy efficiency proposed
• [Lithuania] Online registration required for EEE producers and importers of electric and electronic equipment
• [South Korea] Electromagnetic wave labeling required for wireless equipment
• [Thailand] WEEE management policy and regulation under consideration
• [UK-Scotland] New system for environmental regulation proposed
• [China] WEEE treatment fee imposed on producers and importers
• [EU] Calculation method of recycling efficiency for waste batteries and accumulators provided
• [China] Further hazard prevention and health record- keeping required
• [China] Revised China RoHS II Proposal released
• [Estonia] Suppliers and retailers of energy-related products must now comply with new framework for labelling and product information
• [France] WEEE and waste batteries management further harmonized with EU requirements
• [Germany] Recommendation on Risk assessment of nanomaterials at workplaces released
• [Turkey] WEEE Regulation entered into force
• [EU] Eight substances under consideration as substances of very high concern (SVHC)
• [Germany] Energy related products shall bear energy efficiency label
• [Venezuela] Electric and electronic waste take-back pilot program launched

Global EHS Compliance Insight

From Proactive EHS Compliance to Lobbying

Young & Global Partners

8 September 2012

http://campaign.r20.constantcontact.com/render?llr=rn7iveeab&v=0015qKm9V6FEG5UNsMk_8S9PQxire7yO1uSEJLJsGMHqHK1k9bu_Vs-dIF7wcuyqeB8fWibTCabdY3dvdfkbBVvF0KGcYGZb1nbfRLWmX0KfIQKhtakPayz6brI6aj5-F5I_5Wy8x4-5tme7nJ_VarvLeWDnrQKeWWzfXnRXfwwgCyrBDXWuqbagdArDe9iFvBfujuaeD0SstucqNGqGla32rjvF90O0-W8iJhdMJwkAhy8owNoX15nxuO4K6IOcAwmujAgIfDRmiw5_RSJVPv3aYOEWWAkHytCGA-evONQkemN-Hf_CwkUYFdzziPCqFmjx49Q2SMbP1GjaJAG6SFc2vIMhRQo9tYMmp_wiFsZpUU%3D

THE Pb-FREE IN ELECTRONICS RISK MITIGATION (PERM) CONSORTIUM

A paper has just be released describing the organization, content, and expectations of the newly formed Pb-free Electronics Risk Mitigation (PERM) consortium and its stakeholders. PERM was created as a more focussed group of the LEAP consortium.

The AIA-sponsored Pb-free Electronics in Aerospace  Project (LEAP) has been the premier industry working group in the the defense/aerospace industry since 2004.  It has worked to identify and address the risks and other challenges associated with the use of Pb-free electronics in high performance & high reliability equipment.  It has successfully provided resources such as handbooks and standards as well as templates, guidelines, and other tools to support risk mitigation.  However, the use of Pb-free materials has grown to such an extent that many components/parts are no longer available in tin-lead (either surface finishes or interconnection media).   Engineers have been forced to use some Pb-free parts in their new designs or,  in  many  cases,  as  part  of retrofits and upgrades, leading to concern over performance and reliability.

An ad hoc sub-committee of the LEAP team spent over a year producing a more focused entity called the Pb-free Electronics Risk Mitigation (PERM) consortium, to provide overarching executive leadership and coordination of Pb-free electronics risk management activities for the aerospace and defense community on both the government and industry side.   It is focussed on those activities that provide value-added results.  More information


http://www.ipcoutlook.org/pdf/pb_free_risk_mitigation_smta.pdf

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IPC Solder paste standard emerges

IPC-7527, the first published standard that originated outside the U.S., provides guidance for solder paste.

Solder paste is a necessity for basically all printed circuit boards, but it's one of the most overlooked technologies in the electronics industry. IPC has completed the first standard that will help development teams improve the quality of their solder paste operations, which could bring significant improvements in quality and reliability.

IPC-7527, Requirements for Solder Paste Printing, covers the many aspects of solder paste, from initial placement on the board through tests after boards are ready to move forward on production lines. The standard will cover a large footprint.

"This document is useful for anyone who uses solder paste," said Kris Roberson, IPC's manager of assembly technology. "Before this came together, much of the awareness for solder was 'tribal knowledge' passed from one person to another. That can get to be like the telephone game, where two or three generations down the road the information has changed quite a bit."

The benefits go beyond the unchanging nature of the printed word. The new standard serves as a reference guide for equipment operators. They can now turn to a book when they have questions and can't find the company expert.

"It provides the operators with a standard that will help them make the right decisions when they face with issues in production, and no professionals or specialists are present," Steven Juel Hansen, cochairman of the Solder Paste Printing Task Group and production engineer at Vestas Control Systems A/S, based in Hammel, Denmark.

That Hansen is in Denmark is quite significant. IPC-7527 is the first published IPC standard that originated outside the United States.

"The Nordic group came up with the idea, created the standard and brought a nearly-completed document to IPC. They had done a thorough job. Once they brought it to us it took less than a year to move it to publication. That's pretty speedy given the time needed for public comment and responses, as well as for getting the document ready to publish," Roberson said.

Given IPC's expanding global strategy, it's unlikely that it will be the last. Roberson cites another first for the document, this one on the technical side.

"There are standards that tell what the completed assembly should look like, but this is the first one to tell us what the solder paste should look like," Roberson said. "When things are written down, they provide a common language that clearly specifies requirements. IPC-7527 tells you how far off centers can be before they're considered faulty. In the past, operators did whatever the companies decided to do."

He noted that IPC-7527 is designed to be a useful document for equipment operators and others who work with one of this industry's basic infrastructure elements, solder. Preventing problems with this electrical and mechanical technology can help improve the quality and reliability of many printed circuit boards.

"The standard does a nice job of bringing out common problems, like solder that has rooftops or saddle shapes instead of a nice brick form, and it provides solutions so those issues can be fixed," Roberson said.

When issues like saddles and rooftops arise, the old adage of a picture being worth 1,000 words comes into play. Committee members endorsed that simple saying, packing 50 photos into the 15-page standard.

Though it's fairly short, IPC-7527 addresses a broad range of technologies. It covers solder paste from the early stages through production and testing.

"This covers everything from basic squeegees to jet dispensers and needle dispensers to closed print heads. It also provides information on automated past inspection using either cameras or lasers," Roberson said.

For more information on the standard (already available in English and Danish), visit www.ipc.org/onlinestore.



EMSNow - Solder paste standard emerges:

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5 Key Success Factors for Medical Electronics PCBs

It comes as no big surprise that the market demand for smaller, more compact, handheld medical electronics products is dramatically escalating. The burden is on both the OEM and its contract manufacturer (CM) or EMS Provider to work in close cooperation to expertly deliver the five success factors for medical electronics PCBs. Plus, stringent compliance with ISO 13485:2003 assures the OEM critical requirements are met. This paper gives you the necessary insight into those five success factors and the critical PCB areas the medical electronics Standard covers.

5 Key Success Factors for Medical Electronics PCBs:

IPC Updates Assembly and Joining Handbook

SMTONLINE: For many designers and manufacturing personnel in the electronics manufacturing supply chain, IPC-AJ-820, Assembly and Joining Handbook, is the document of choice for all aspects involved in creating a PCB. With input from leading OEMs and research facilities, the recently released “A” revision of this industry handbook contains updated information on proven techniques for the assembly and soldering of electronic assemblies.

“IPC-AJ-820A covers 14 topics in 289 pages, addressing everything from handling to design to component selection and soldering,” says Kris Roberson, IPC assembly technology manager. “The handbook gives users basic data such as terms and definitions as well as the technical, more nitty-gritty, down-and-dirty information.”

With no shortage of in-depth information, the handbook includes equations for designers as well as techniques for tin whisker mitigation. A section titled “tin pest” explains how parts with high tin content can break down to powder under certain conditions.

Rising to the Challenge of Pad Cratering

Rising to the Challenge of Pad Cratering: "However, it's been difficult to determine what materials will work best in varied applications. 'In the beginning, there wasn't much attention to these types of failure because they were almost unheard of. But more companies started getting products ready to ship and realizing they had a problem that was not with one or two parts, but with many. These are catastrophic failures that are sometime latent. The defect doesn't always show itself in testing,' said Reza Ghaffarian, a NASA Jet Propulsion Lab Engineer."

That will help alleviate an issue that has become a major challenge for many manufacturers. "With the transition to lead-free solder and halogen-free PCB materials, one of the primary failure modes for lead-free BGAs is when copper pads on the board are pulled up, which causes pad cratering," said Satish Parupalli, an Intel engineer who helped coordinate the development of the IPC-9708 within the IPC 6-10d task group. "Assuming no manufacturing defects and test issues, people agree that the resin material is a driving factor for this failure mode. But with the transition to lead-free, there's been no one technique that helped us identify what changed in resin materials that caused this problem."

IPC Updates Assembly Standards

EMS007 IPC Updates Assembly Standards: "IPC has updated a pair of joining and assembly standards, making them easier to use and adding information in areas that have evolved. IPC J-STD-001E and IPC-A-610E have also been more closely linked to eliminate differences that could prove costly to users.

The two documents are related, but there are significant differences. IPC-A-610, Acceptability of Electronic Assemblies, is a visual acceptance standard. It has criteria and illustrations to show how connections need to appear after assembly; the illustrations help users understand the written requirements."