Answers to SMT Quiz

Folks,

A few weeks ago, I posted an SMT quiz on my blog. We received 178 responses, which seemed very good to me. Working with my Indium Corporation colleagues, we came up with the titles below, depending on your score. The percent of respondents that obtained the different titles is also listed.

10 correct responses - SMT Guru: 11% (19)
8-9 correct responses - SMT Expert: 41% (72)
6-7 correct responses - SMT Leader: 35% (63)
4-5 correct responses - SMT Teammate: 10% (18)
3 or under correct responses - SMT Trainee: 3% (6)

We also had five lucky winners of a $25 digital gift card.

Perhaps we will do another quiz in the near future.

The answers to the quiz can be found below. The correct answer is in bold.

1. What concern exists when mixing tin-lead and tin-bismuth solders?
   1. Bismuth will not alloy with lead
   2. Tin-bismuth-lead can form a low melting point alloy
   3. There is no concern
   4. The bismuth will precipitate out
   5. The lead will precipitate out
2. How much copper is in SAC305 solder?
   1. 3.0 %
   2. 0.3%
   3. 3.5%
   4. 0.5%
   5. None of the above
3. Which temperature is closest to SAC305’s melting point?
   1. 230C
   2. 210C
   3. 183C
   4. 220C
   5. 200C
4. What does OSP stand for?
   1. Organic solderability preservative
   2. Organic solderability protectant
   3. Operational soldering procedure
   4. Operational soldering process
5. What does ENIG stand for?
   1. Energizing nitrogen gas
   2. Electroless nickel gold
   3. Evolving nitrogen inerting gas
   4. None of the above
6. In solder paste, what is response to pause?
   1. When paused, when stirring the viscosity decreases
   2. Whether or not the paste viscosity changes when printing is paused
   3. Whether or not the paste dries out when printing is paused
   4. When printing is paused the flux separates from the paste and makes a mess
7. What is more typical of a solder paste powder diameter:

1. 5 mils
2. 30 microns
3. 25 mils
4. 5 microns

8. The formula for aspect ratio (AR) for a stencil aperture is: d/t, where t is the stencil thickness and d is the line width. Assuming the stencil is 5 mils thick, what is the finest line that can be reliably printed? A rule of thumb is the AR should be ≥1.5.
   1. 5.5 mils
   2. 3.5 mils
   3. 7.5 mils
   4. 10 mils
   5. 4.5 mils
9. Assume that component placement is the “gate” in an SMT assembly process line, which has one chip shooter and one flexible placement machine. The chip shooter takes 60 seconds to place its components. While the flexible placer takes 45 seconds. There are some chips being placed by the flexible placer. To improve productivity, what should be done?
   1. Nothing, everything is fine
   2. Chips should be taken off the flexible placer and put on the chip shooter as chip shooters are best to place chips.
   3. Chips should be removed from the chipshooter and placed on the flexible placer to time balance the line
   4. The chip shooter is so slow, move all of the components to the flexible placer
10. What is a fiducial on a printed wiring board?
    1. It shows the PWB manufacturer that the etching process is within specification.
    2. It is used to align the PWB to the assembly equipment
    3. It is needed as a reference for solder mask
    4. It is the most cost effective way to minimize PWB warpage.

Cheers,

Dr. Ron