A two-phase study to assess how to completely clean underneath leadless devices following soldering with Pb-free water soluble and Pb-free no-clean pastes.

Ed.: Part 1 was published in the August issue.

Phase 2 methodology. In this phase of the study, eight pastes were evaluated: four water-soluble lead-free (Pastes A, B, C and D) and four no-clean lead-free (Pastes E, F, G and H). Additionally, Practical Components’ PCB007 test vehicle was used. In this case, boards and components were provided to RIT, where they were screen-printed and reflowed. Following reflow, the assembled boards were returned to Zestron and cleaned within 24 hr. of reflow in an Aquastorm AS200 inline cleaner using the dynamic surfactant and optimized wash parameters from Phase 1 (see Table 6, previous issue). Cleanliness assessment followed, including visual inspection and ion chromatography, each conducted at Zestron. Regarding visual inspection, the same protocol used in Phase 1 was employed for Phase 2.
In total, 24 test boards were assembled or three with each paste type. Of the three board sets, two were used for ion chromatography analysis and one for visual inspection. Each board was populated with the component quantities as detailed in Table 7. For reflow, RIT employed a six-zone industrial oven. Refer to Table 8 for the reflow zone set points and Figure 13 for the documented reflow profile.

Following reflow, visual inspection using a Keyence VHX-1000 microscope confirmed standoff height at 2 mil (Figure 14).

Phase 2 results: visual inspection. Of the 24 boards assembled for Phase 2, eight boards (one with each paste type) were visually inspected on the surface, as well as underneath the components utilizing the same protocol as that used in Phase 1, following the cleaning process. Optimum cleaning parameters identified in Table 6 were held constant throughout Phase 2 trials. Using these parameters and maintaining the wash temperature at 145°F, all water-soluble pastes were fully cleaned on the board surface underneath all components. However, as suspected with the no-clean pastes, MLF-68 components reflowed with Pastes F and H, as well as all the dual-row components, required 155°F wash temperature to achieve full cleanliness.

The determination to increase wash temperature was made during the visual analysis. Since multiple boards were prepared for each paste, and each board was cleaned individually, wash temperature adjustments were made as required for subsequent trials.

Thus, for the no-clean pastes, the following observations were made:

Pastes E and G:
Completely cleaned underneath MLF-20, MLF-44 and MLF-68 components using process parameters determined in Phase 2.
Dual-row MLF-156 components were completely cleaned underneath at 155°F wash
temperature.

Paste H:
Completely cleaned underneath MLF-20 and MLF-44 components using process parameters determined in Phase 1.
Completely cleaned underneath MLF-68 and dual-row MLF-156 components at 155°F wash temperature.

Paste F:
Completely cleaned underneath MLF-20, MLF-44 components using process parameters determined in Phase 1.
Completely cleaned underneath MLF-68 components at 155°F wash temperature.
Slight residues remained under one of three dual-row MLF-156 using 155°F wash temperature.

Table 9 shows wash temperature requirements for full cleanliness underneath all components.

Surface residues were completely removed on all boards with all paste types. Figures 15, 16, 17 and 18 are representative of the cleanliness level achieved underneath for all four component sizes.

Phase 2 results: ion chromatography. Sixteen boards (two for each paste type) were assembled for ion chromatography analysis. Ion chromatography analysis was performed to characterize ionic residues on the board surface in terms of anions (fluoride, acetate, formate, chloride, nitrite, bromide, nitrate, phosphate, sulfate), cations (lithium, sodium, ammonium, potassium, magnesium, calcium) and weak organic acids. If contaminants are present on electronic assemblies and bare boards, they contribute to electrochemical failures when mixed with moisture and applied voltage.³

Ion chromatography testing was performed according to IPC-TM-650, method 2.3.28.3 Test equipment used enabled analysis of anions, cations and weak organic acids. All boards tested resulted in contamination levels well below IPC limits. Ion chromatography results are detailed in Tables 10, 11, 12 and 13 (Appendix).

Conclusion

Effective cleaning of flux residues underneath low-standoff components is difficult and is made more so as component surface area increases. However, as this study has proved, this challenge can be met with an appropriate cleaning agent and optimized cleaning process.

Flux type is certainly a critical factor, and water-soluble flux residues are more easily cleaned compared to the no-clean flux residues.

For water-soluble flux residue, cleaning agent concentration, wash exposure time and spray configuration proved less critical for achieving full cleanliness underneath the components.

For the no-clean flux residue, higher cleaning agent concentration, increased wash exposure time and the eight spray bar manifold with the intermix nozzle technology resulted in better cleaning results underneath all QFN components. In several cases (depending on paste type and component configuration), an increase in wash temperature was required as well in order to fully clean underneath the QFN.

As indicated in Table 9, slight residues remained under one of six dual-row MLF-156 components. However, it should be noted that all boards subjected to ion chromatography testing resulted in contamination levels well below the standard limits.

Although specific no-clean paste types, as well as the MLF size, influence the process parameters required to clean underneath components, this study confirms through visual inspection underneath all QFN types, as well as with ion chromatography results, that a dynamic surfactant cleaning agent and optimized inline cleaning process can fully clean the surface underneath low-standoff QFNs.

References
2. Harald Wack, Ph.D., Umut Tosun, Joachim Becht, Ph.D., Helmut Schweigart Ph.D., “Why Switch from Pure DI-Water to Chemistry?” SMTA International Proceedings, October 2009.
3. IPC-TM-650, Test Methods Manual, Method 2.3.28, Ionic Analysis of Circuit Boards, Ion Chromatography Method, May 2004.

Acknowledgments
Special thanks to ERSA North America for providing the 10 zone ERSA HotFlow 3/20 reflow oven, Rochester Institute of Technology for populating and reflowing test boards, Speedline Technologies for providing the Aquastorm 200 inline cleaner, and StenTech for providing the stencils for this study.

Ed.: This article was originally published in the Proceedings of SMTA Penang in April 2013, and is republished here with permission.

Umut Tosun is application technology manager; Naveen Ravindran is application engineer, and Michael McCutchen is the former vice president Americas and South Asia at Zestron; u.tosun@zestronusa.com.

Dynamic capacity planning incorporates the randomness and variability of the real world.  It shows you how to target your capital equipment (capex) spending to attain throughput and cycle-time goals for millions of dollars less than with spreadsheets.

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Our annual survey finds a quarter of PCB designers are nearing retirement, but salaries have never been higher.

If a recent survey is any indication, printed circuit board designers are becoming an even more experienced crowd and have concerns about their workload, yet their salaries are increasing slightly with age.

From May 1 to June 30, a total of 421 bare board designers responded to PCD&F’s annual salary survey. The online survey covered salaries, job functions, titles, project types and quantity, benefits, education, experience, career challenges, locations, ages, and company demographics, to name some. Results are intended to provide a snapshot of the state of design industry jobs, not a meticulous scientific study.

Of the 421 respondents, just over half (50.4%) say they are senior PCB designers, down from 56% in the 2012 survey. PCB designers account for 16.9% of respondents, compared to 15% last year. Other common job titles include design engineer (7.6%), PCB design manager (7.6%), hardware engineer (4.3%), and senior engineer (3.6%). CAD librarians made up 2.6% of those responding.

As in 2012, respondents overwhelmingly say their principal job function is PCB design (including schematic, layout, placement, etc.) (Figure 1). Next is PCB engineering, with 11.9% of responses, followed by design/layout management, engineering management, and ECAD librarian.

The majority of designers continue to work for OEMs (66.3%). Another 11.2% work for design service bureaus, compared to 10% in the previous year. Strikingly, relatively few – 1.9% –  of respondents indicated they work for a contract assembler, despite the increase in those services among EMS providers.

As the 2012 and 2013 surveys have shown, for a significant portion of designers, retirement is looming. Over a quarter of respondents (25.4%) have more than 30
years’ experience in the business, compared to 21% last year (Figure 2). Some 57.7% of participants in this year’s survey have more than 20 years of experience, compared to 53% in 2012. Only 17.3% say they have 10 or fewer years’ experience, flat with 2012.

Along those lines, 24.9% of respondents are between the ages of 51 and 55, the demographic most represented in the survey. More than half (58.6%) fall between 46 and 60, compared to 55% last year. In 2013, 8.8% of respondents are 60 to 70 years old, compared to 10% in 2012, and two respondents are over 70. In the younger age brackets, 10.2% are 41 to 45, flat with last year, and 14.7% are 31 to 40, down from 16% last year. Just 7.1% are 30 or younger, and no one who responded to the survey is younger than 20.

The demographic of designers is still resoundingly male, with 89.3% of responses, up from 86% in 2012’s survey.

Top earners. With the veteran population growing in the design industry, so are salaries. The top earners make over $150,000. Nearly one-third of designers make between $70,000 and $90,000 a year (Figure 3), and 34.1% earn more than $90,000, compared to 28% last year. Of the designers who took the survey, 74% make more than $60,000, up one percentage point from 2012. Only 7.2% bring in $20,000 or less, compared to 8% last year.

While the clear majority of respondents say their salaries increased in the past year – 72%, up from 69% in 2012 – the increases were modest, with 48.2% of respondents’ salaries growing 1 to 3%. Another 14.3% say their salary rose 4 to 6%, and 6.2% report a salary increase of 7 to 10%. More than 21% of survey respondents say their salary did not change in the past year. About 7% of respondents said their salary decreased, which was consistent with the previous survey.

More than half the respondents say they did not receive an annual bonus in the most recent year (53.4%). In the 2012 survey, 56% said they did not receive a bonus. Though the frequency of bonuses appears to have improved, based on responses, the amounts are less. Of those who recently received a bonus, 55.1% say the extra cash, on average, is 1 to 3% of their current salary, compared to 43% of respondents in 2012. Another 24.4% say 4 to 7%, down from 29% last year, and 20.5% say more than 7% of their salary, compared to 28% in 2012.

A vast majority of respondents say they live in the US (70.7%) (Figure 4); this figure is slightly down from 73% in the 2012 survey. The West Coast of the US (including Arizona) accounted for 22.3% of respondents, compared to 23% last year. Another 16.9% live in the Midwest, while 16.6% are in the Northeast/New England/Mid-Atlantic. Some 8.6% of responses came from Central/Western Europe, compared to 9% last year. There were a trickle of respondents from China, perhaps owing to the survey only being conducted in English. Two designers from Africa/Middle East responded, however.

Tech trends. Technology is always advancing, but sometimes not as fast as we would think. Designers were asked what types of projects and/or technologies they directly engineer, design or lay out. The most common response? Four to 6 layer PCBs, followed by double-sided boards. Yet use of BGAs, CSPs, HDI and embedded systems are on the rise (Table 1).

More than a quarter of the designers who responded to the survey (25.2%) say they produce, on average, 6 to 10 new designs each year, down from 29% last year. Another 21.1% say they produce 11 to 15 new designs annually, up from 18% in 2012. Just over 15% produce 1 to 5, flat with the previous survey, and 11.9% say 16 to 20 new designs, compared to 14% last year. Some 10.2% produce 21 to 30 new designs, on average, annually, up from 8% in 2012. Another 16.4% produce more than 30, nearly flat with last year.

Designers are an educated group (Figure 5). More than 31% say they have a one to two-year associate’s degree; another 24.5% have some college, but no degree, for a total of 55.6%, compared to 60% in 2012. More designers this year say they have a bachelor’s degree in engineering or a related field (28.5%), up from 21% last year. Fewer designers this year reported either a master’s degree or Ph.D.

Fewer designers also say they are an IPC Certified Designer (30.9%); in 2012, this number was 33%. Of the designers who are IPC certified, 57% say they are CID; 43% say CID+.

Government/military/aerospace/avionics/marine/space garnered the most responses (again) when designers were asked which end-market they primarily design for, with 22.6%, compared to 23% who said “high-reliability products” last year (Figure 6). Communications/related systems equipment (including all phone types) is a close second, with 16.6%. Industrial controls/equipment/robotics received 13.5% of responses, and consumer electronics another 9%, down from 11% in 2012. Other end-markets are electronic instruments/ATE design and test (8.8%); medical/optical electronics and equipment (8.1%); other (6.2%); computers/peripherals (5.5%); automotive/other ground vehicles (5%), and semiconductors and related packaging (4.8%).

Designers are keeping their jobs. Some 93.3% say they have the same job as 2012, up from 91% in the previous survey. Nearly 7% were laid off in the past year, comparable with the 2012 survey.

Workload is still designers’ biggest challenge, with 51.8% stating so, up from 49% in 2012. Other challenges include technology (35.6%), nearly flat with 2012, and finding/keeping one’s job (34.9%), also flat with last year. Outsourcing received fewer responses than the previous survey, with 22.1%, down from 25%.

A large portion (72.9%) of designers who completed the survey do not have other staff members reporting directly to them. Some 18.8% say they have 1 to 5 people reporting to them, nearly flat with last year. Only 4.8% say they have six to 10 people reporting to them, and another 2.1% oversee 11 to 20 staff. Just over 1% have more than 20 employees reporting directly to them.

When asked their highest level of purchasing power, 31.8% of designers say they recommend products, down from 36% last year. Some 23% evaluate products, up from 20% in 2012. Another 17.6% have the ability to specify products, compared to 17% last year, and 12.1% approve product purchases, up from 8% in the prior survey.

Among the products and services evaluated, recommended, specified or approved, CAD software led with 78.9%. Prototype PCB services garnered 56.5% of responses, while design services pulled in 36.6%. Here’s how the rest of the list breaks down:

• Active/passive components: 30.4%
• Connectors and cables: 29.9%
• Assembly services: 29.7%
• Volume PCB fabrication services: 28%
• CAM software: 27.8%
• Substrate materials: 20.9%
• Solder mask: 20.7%
• Computers and peripherals: 19%
• CAE software: 18.1%
• FPGAs/PLDs: 15.4%
• Consulting services: 15.2%
• Solder materials (paste, flux): 12.8%
• Epoxies and finishes: 11.6%
• Test/measurement services: 11.4%

Designers still work for large firms. When asked how many staff members their company employs, 43.7% said more than 1000, up from 40% in 2012. Another 16.4% work for firms with 251-1000 employees, compared to 18% last year. About 10% work at companies with 101-250 employees, down from 13% in 2012. Other responses include 51 to 100 employees (7.4%); 26 to 50 employees (6.7%), and 25 or fewer staff members (15.7%), compared to 14% in 2012.

The distribution by company revenue was fairly even. Between 7% and 11% worked for firms with sales of less than $5 million, $50 million to $100 million, $100 million to $500 million, and $500 million to $1 billion. Fifteen percent work for firms with annual sales topping $5 billion; 13.8% work at companies with sales of $1 billion to $5 billion, and 16.4% work for firms with sales of $5 million to $50 million.

The picture of company benefits looks remarkably similar to data compiled in 2012. Leading the way again is health insurance, with 86.9% of companies offering this, and 73.9% offering dental insurance. Life insurance is provided to 72.4%, and some 67% are offered a 401(k) plan. All these figures are consistent with the 2012 survey. Other benefits include:

• Cafeteria: 44.4%
• Stock purchasing plan: 33%
• Company pension or retirement plan: 28.7%
• Exercise room/equipment: 28.7%
• Profit sharing: 24%
• Telecommuting: 20.7%
• Relocation expenses: 14.3%
• Daycare facilities: 4.3%
• Sabbatical: 4%

Many companies support educational opportunities, with tuition reimbursement leading responses at 56.1%. On-the-job training is supported by 50.6% of companies who employ survey respondents. About 45% reimburse for conferences, and about 40% conduct company classes. Mentoring is supported by 27.1%, and college classes are supported by 18.1%.

To view results of the 2012 survey, visit http://pcdandf.com/cms/component/content/article/246-2012-articles/8976-designers-salary-survey.

Chelsey Drysdale is senior editor for PCD&F/Circuits Assembly; cdrysdale@upmediagroup.com.

A two-phase study to assess how to completely clean underneath leadless devices following soldering with Pb-free water soluble and Pb-free no-clean pastes.

Read more ...