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#1. What is the ideal aspect ratio for microvia?
2:1 #2. Why is a smaller aspect ratio better for vias?
The reliability of the plated through-hole will be higher.
Smaller aspect ratios eliminate the need for via copper plating.
Smaller aspect ratios are more cost-effective. #3. What is the main difference between plated holes (PTH) and non-plated holes (NPTH)?
PTH conduct signals whereas NPTH are used to position components.
NPTH are more cost-effective than PTH.
PTH cut down on parasitic inductance whereas NPTH do not.
PTH and NPTH have different tolerances. #4. Which via should be used to save space on the outer layers of a PCB?
Microvia #5. Which of these statements about via hole drilling is false?
Mechanical drilling is used for through-holes and back drilling.
Laser drilling is used for blind and buried holes.
Laser drilling is used for through-holes and buried holes.
Laser drilling enables smaller drill diameters than mechanical drilling. #6. What is the name of the pad around the hole in a via?
Drill to pad ratio
1 and 2 are correct. #7. According to IPC standards, the diameter of buried and blind vias should be:
≦ 6 mils
≦ 5 mils
≦ 7 mils
≦ 4 mils #8. What is the main reason to choose via-in-pad over conventional vias?
To handle high package densities in HDI boards where routing is critical.
To decrease the manufacturing cost of a PCB.
To increase signal integrity.
To increase the structural integrity of the PCB. #9. Why does via-in-pad require a non-conductive epoxy fill?
To improve thermal insulation between laminates.
To avoid solder to sip into the via in components like BGAs.
To add to ease of manufacturing.
To be cost-effective as compared to solder masking. #10. When do you implement back-drilling?
When minimizing the aspect ratio.
When using conductive epoxy via fill for the via-in-pad.
For planarization of copper plating.
To remove via stubs to improve signal integrity. #11. Which of the following is not part of the PCB via finish process?
Plating #12. What is the purpose of DFM?
To assess the viability of manufacturing.
To finalize the product design.
To eliminate issues in previous product designs. #13. What is the difference between vias and pads?
They are the same.
Vias are used to electrically interconnect the layers. Pads are used to interconnect and provide mechanical connections for SMTs.
Minimum pad width 0.15mm / minimum via width 0.20mm
The via size is smaller than the pad size #14. What is the IPC standard for via size and tolerance?
IPC-2221 #15. Choose the correct statement for thermal vias.
Thermal vias are non-plated vias.
The standard diameter for thermal vias is 0.15mm.
No via filling is required for thermal vias.
1 and 3 are correct. #16. Which of the following is a wrong statement regarding thermal management?
Thermal vias are used to increase thermal conductivity.
Thicker solder joints can increase the accumulation of heat.
Combination of microvias and buried vias increase heat accumulation.
You can reduce the size of thermal vias in order to reduce the overflow of the solder into the vias. #17. Select the standard that governs via construction in flex PCBs.
IPC-6012 #18. Which of the following is not a filling technique used to fill stacked vias?
Conductive paste and cap plating
Non-conductive filling, metallization, and cap plating
Special high-throw electroplating that will fill the via
Back drilling of vias #19. Which is the cost-effective way to connect microvias from one layer to another?
Any-layer vias #20. Name the via structure used in the picture.
Any-layer vias #21. Which of the following is a wrong statement about vias used in flex PCBs?
Vias in flex PCBs should be larger compared to vias used in rigid PCBs.
Low width annular rings are good for flex boards.
Fix vias in areas where there is limited or no bending.
Deep-plated barrels with higher stretching and compressing forces result in cracking the vias while bending. #22. Name the routing method where a via is offset from the pad and placed at the center of four pads.
Dogbone routing #23. What is the difference between via stitching and via shielding?
Via stitching is a technique used to tie larger copper areas on different layers and via shieldings are used in RF designs to reduce crosstalk.
Via stitching is used to reduce electromagnetic interference and via shielding provides a strong vertical connection.
Via stitching and shielding do the same functions. #24. Which is not a function of via stitching?
Maintaining low impedance for power and ground planes.
Tying copper areas.
Placing one or more rows of vias alongside the signal's route.