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Good Board vs. Bad Board

Reducing Time on Debugging Boards and Improving Design Yield

Summary

Tests with the EMxpert EHX were done on two different designs at the production facility of a Contract Manufacturer in Norway (CM). Samples of each design were presented both with problems and without. The tests were done to determine if the problems could be identified when comparing the very-near magnetic field emissions of the good boards and the problem boards.

The problem of the first design was identified by comparing the very-near-field spatial scans at 1.48 MHz. A lack of detected current correlated with what the CM suspected was a failed component.

The second design was presented with a problem that had been eluding detection. It showed as a poor RSSI reading and had been isolated to the IF chain. A comparison of the IF currents between a good board and the problem board indicated an issue in a location different from where the CM had assumed the problem was. Further investigation uncovered a soldering issue with a single component.

With both designs, we were able to detect issues in the very-near-field emissions which would have and did assist the CM engineers in tracking down root causes.

The initial scans took a long time to complete since we were not familiar with the design or the expected results. With the proper initial work done on a given design this tool could be very effective at quickly identifying issues in the complex designs that Kitron works on.

Setup

For all tests the CM test boards were placed on the EMxpert EHX. For the first design only the bottom side of the board was measured because a heat sink was present over the entire board on the top side. Modifications to this heat sink would allow testing of both sides of the board.

For the second design both top and bottom side were measured.

All testing was done with the Keysight Fieldfox N9912A. This instrument is part of EMSCAN’s standard demo kits and is much slower than a benchtop spectrum analyzer. Using a faster spectrum analyzer would be another way to improve the analysis time.

Board 1 Test Results

This section includes the results from the first design. This design was an underwater acoustic sensor. The spectral emissions of the bad board did not indicate a problem by itself but it displayed the peak frequencies that needed to be analyzed closely. Knowledge of the design and the problem provided by the CM also helped narrow down the frequencies that needed to be looked at.

Figure 1 – Spectral emissions of a bad board for Design 1

This spectral scan was a small sample of all emissions coming from the board. In this region the spatial analysis did show variation in areas of the board that correlated with suspected problems. This is shown in the spatial images below.

Figure 2 – Spatial emissions of a bad board at 1.48 MHz showing a quiet area of the board

The image above shows a noticeable lack of currents at the component that was suspected to be the cause of the problems. To confirm whether this is in fact an anomaly an equivalent scan of a good board was done. The good board does show a noticeable difference specifically in this area.

Figure 3 – Spatial results from a good board at 1.48MHz

A spatial scan focused on the area where the difference is confirms that currents are detected along the expected traces.

Figure 4 – Spatial results from a good board showing the critical location with currents present

Board 2 Test Results

This section includes the results from the second design. This design was a 2.7 GHz receiver. Information provided by the CM indicated that the problem was related to the IF chain. A scan of the entire board at the IF frequency clearly showed a difference in the spatial profile.

Figure 5 – Spatial scan of the good board at the IF frequency

Figure 6 – Spatial scan of the bad board at the IF frequency

Once it was confirmed that there was a problem at the IF frequency a focused analysis on the IF chain was done. Zooming in on the area of the IF right as it exited the first mixer showed a very-near-field emission variation immediately following the SAW filters.

Figure 7 – Spatial scan of the IF chain of the good board showing strong emissions throughout

Figure 8 – Spatial scan of the bad board at the IF frequency

After viewing the large variation in the very-near-field emissions at this location, a visual inspection of the board revealed the SAW filter highlighted in the image above was populated with a 90° rotation meaning no signal would pass through.

Conclusion

The EMxpert EHX has shown itself to be an extremely useful tool for identifying differences between good and bad boards. In these examples it took a couple of hours to get baseline analysis of the good boards done. This would normally be the case for a new design. However once these baselines are done it should be possible to quickly identify locations of the board which may be causing problems.

The EMxpert EHX should reduce the amount of time spent debugging boards and should improve the yield of design which are currently problematic to debug.

Why EMxpert Is Right For You

You can execute real-time analysis of your design, test multiple design iterations and optimize complex designs on your lab-bench in seconds at each stage of the design process.

You want to avoid the delays and set-up needed for far-field measurements in a chamber.

EMxpert not only require low CAPEX and zero OPEX, they also deliver significant ROI advantages.

Key Benefits

Test results in seconds
Easy to use
Compact and tabletop
Significant time-to-market acceleration
Dramatic increase in production
Substantial cost reduction

Read More

Are you under time-to-market pressure because of the countless number of lengthy measurements in inaccessible anechoic chambers?

Tired of losing valuable project time waiting in line to test your designs in expensive anechoic chambers?

Do you want to test your design and performance quickly to accelerate project completion and delivery?

Are you under budget pressures?

Why did your product fail the compliance test in an anechoic chamber? Why didn’t you see this coming?

With EMxpert, in seconds and a fraction of an anechoic chamber cost you can easily:

  • Analyze your high speed, high power and/or high density/complexity PCB designs.
  • Visualize the root causes of potential EMC and EMI problems.
  • Find, characterize, and address unintended radiators or RF leakage.
  • Pinpoint the cause of a design failure even when the problem is intermittent.
  • Prototype, test, and optimize new designs, forms and components.
  • Test & optimize multiple PCB (printed circuit board) design iterations on your lab-bench.
  • Resolve EMC and EMI problems early in the design cycle
  • Display NFC antenna emissions

…all for a fraction of the cost of an anechoic chamber.

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  •   How does the EHX work?

    how-does-it-workThe EMxpert EHX consists of a patented scanner, a compact adapter, a customer-supplied spectrum analyzer and a PC running EMxpert software (EMxpert setup diagram). The EMxpert EHX measures the magnetic field (H-Field) in two orthogonal directions using H-field probes.

    The patented scanner is a passive device that couples the very-near-field emissions from the device under test. The measurements of these coupled fields are done with the spectrum analyzer and the adaptor synchronizes the spectrum analyzer and the patented scanner.

    The EMxpert software knows the insertion loss of each individual probe across the frequency range so it can apply compensation for the internal losses of the scanner.

    The software will also apply the antenna factor compensation that will result in accurate H-field data being displayed. Interpolation between probes is done by the software so that features smaller than the probe spacing can be resolved.

    The patented scanner consists of 1,218 H-field (magnetic) probes that operate between 150 kHz and 8 GHz. Probes are wide band but not very sensitive across this band thus they are very good at rejecting background noise.

    Each row and column on the patented scanner corresponds to a unique probe that is spaced every 7.5 mm into an electronically switched array, which provides an effective 3.75 mm resolution. Electronic switches enable the probes to sweep the entire board under one second.

  •   How does the EHX+ work?

    how-does-it-workThe EMxpert EHX+ consists of a patented scanner, a built-in adapter, a built-in spectrum analyzer and a customer-supplied PC running EMxpert software (EMxpert setup diagram). The EMxpert EHX+ measures the magnetic field (H-Field) in two orthogonal directions using H-field probes.

    The patented scanner is a passive device that couples the very-near-field emissions from the device under test. The measurements of these coupled fields are done with the spectrum analyzer and the adaptor synchronizes the spectrum analyzer and the patented scanner.

    The EMxpert software knows the insertion loss of each individual probe across the frequency range so it can apply compensation for the internal losses of the scanner.

    The software will also apply the antenna factor compensation that will result in accurate H-field data being displayed. Interpolation between probes is done by the software so that features smaller than the probe spacing can be resolved.

    The patented scanner consists of 1,218 H-field (magnetic) probes that operate between 150 kHz and 8 GHz. Probes are wide band but not very sensitive across this band thus they are very good at rejecting background noise.

    Each row and column on the patented scanner corresponds to a unique probe that is spaced every 7.5 mm into an electronically switched array, which provides an effective 3.75 mm resolution. Electronic switches enable the probes to sweep the entire board under one second.

  •   How does the ERX+ work?

    The EMxpert ERX+ consists of a patented scanner, a built-in adapter, a built-in spectrum analyzer and a customer-supplied PC running EMxpert software (EMxpert setup diagram). The EMxpert ERX+ measures the magnetic field (H-Field) in two orthogonal directions using H-field probes.

    The patented scanner is a passive device that couples the very-near-field emissions from the device under test. The measurements of these coupled fields are done with the spectrum analyzer and the adaptor synchronizes the spectrum analyzer and the patented scanner.

    The EMxpert software knows the insertion loss of each individual probe across the frequency range so it can apply compensation for the internal losses of the scanner.

    The software will also apply the antenna factor compensation that will result in accurate H-field data being displayed. Interpolation between probes is done by the software so that features smaller than the probe spacing can be resolved.

    The patented scanner consists of 1,218 H-field (magnetic) probes that operate between 150 kHz and 8 GHz. Probes are wide band but not very sensitive across this band thus they are very good at rejecting background noise.

    Each row and column on the patented scanner corresponds to a unique probe that is spaced every 7.5 mm into an electronically switched array, which provides an effective 3.75 mm resolution. Electronic switches enable the probes to sweep the entire board under one second when Level 1 is selected.

    The scanner is placed right under the Gorilla Glass. X/Y step motors move the scanner (1218 probes) for higher resolution scans under the Gorilla Glass. After placing the DUT on the Gorilla Glass, user can select from seven different levels of resolution (0.12 mm – 7.5 mm).

    The image on right is a representation of a 2 x 2 scan area on the scanner. At level 1, spatial scan is executed in real-time i.e. scanner doesn’t move. The data is collected by each probe that is placed in the center of each grid.

    At level 2, each grid is divided into four subgrids. Scanner first moves the orange dots and collects data from four subgrids. Scanner then moves to black dots and collects data from four subgrids. Scanner then moves to green dots and collects data from four subgrids and finally, scanner moves to purple dots and completes the scan.

    At each level, one grid is divided into four subgrids which means four measurement points. Level 7 is the highest resolution (120 microns) and the maximum number of measurement points in one grid can be 4,096.

Companies Who Trust EMxpert Products
What Our Customers Are Saying
“I’m an electronics technician with 30 plus years in the automotive electronics field. We could not afford to spend a lot of time and money at the end of the development cycle trying to fix EMC failures, especially at the expensive certified EMC labs that we used for final compliance testing. Our in house EMC lab was used for pre-compliance testing, we were not certified. For susceptibility testing we did: strip line, TEM cell, tri-plate and bulk current injection. This is where EMxpert comes in. When you’re doing susceptibility testing and there is an anomaly, it may not be apparent as to what part of the circuit is malfunctioning. For EMC, it is all about the up-front work that is done. Board layout and pre-compliance testing are very important. The farther into the design cycle you are, the more it will cost you to resolve it. If I had to describe EMxpert in one word it would be “up-front”. It’s like your headlights in the dark.”
Tom Livingston
Lectron
“I was very impressed with the capability of the EMxpert solution. We had spent several weeks investigating EMC issues related to our end customers product. We had information relating to the spectral component and amplitudes that were causing an issue, but needed to identify the location of the emission site. The EMxpert tool allowed us to perform spatial analysis and locate the site in a single day. The tool is effective and can save weeks of time and effort!”
Iain Lochhead
Semtech Director of Applications Support
“Where have you guys been for the last 5 years while we have struggled?” was the concluding comment from Robert… “We need one of these” was Robert’s conclusion.”
Robert Dmitroca
Senior Design Engineer - EMI
“I was very impressed with the capability of the EMxpert. The EMxpert tool allowed us to perform spatial analysis and locate the site in a single day. The tool is effective and can save weeks of time and effort!”
Director of Applications Support
Leading Semiconductor Manufacturer

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