Indium Blog

Test Your SMT IQ

  • SMT Solder

  • Folks,

    Mary had worked at a small SMT “mom and pop” shop for 12 years. Business was always good and she moved up to CFO of the 60 person company. Revenue had been over $12 million for a few years with profits north of $1 million each year. She marveled how well Fred, the owner,  managed the small firm. As CFO, she was well aware of the strong financial strength of the company.

    Mary was stunned when 18 months ago, Fred said he wanted to retire in less than two years, and he wanted her to "buy him out." Fred was fit and spunky, but 75 years old was now in the rear view mirror.

    Mary was more than stunned by the price Fred wanted; it was way, way too low. She even “complained” about this. But, Fred considered her more as a daughter and insisted on the low price. However, one of the concerns they both had was that Fred was really also the chief engineer. They had many loyal workers, as Fred paid 50% over the local rate and provided great benefits, but no one could fill in for Fred in the technical aspects of running the shop.

    Fred had been trying to coach Mary for the past 18 months so that she would understand the technical aspects of SMT assembly better. Mary was a fast learner, but with only 6 months left before Fred’s retirement, they both agreed they needed to hire a chief engineer.

    So, Fred developed an SMT IQ Test for the candidates. If they could not get at least 80%, they would not be considered. Fred argued that if you were really good enough, you had to know 80% of these questions. Here they are:

    1. What does the “A” in SAC305 stand for?
    2. The belt speed on a reflow oven is 2 cm/s. The PCB with spacing is 36 cm. What is the maximum time that the placement machines must finish placing the components on the PCB to keep up with the reflow oven?
    3. In mils, what is a typical stencil thickness?
    4. BTCs are one of the most common components today. A subset of BTCs is the QFN package.
      • What does BTC stand for?
      • What does QFN stand for?
    5. What is the melting temperature of tin-lead eutectic solder?
    6. In mm, what is the finest lead spacing for a PQFP?
    7. Are solder pastes thixotropic or dilatant?
    8. In stencil printing, what is response to pause?
    9. For a circular stencil aperture for BGAs or CSPs, what is the minimum area ratio that is acceptable?
    10. What are the approximate dimensions of a 0201 passive in mils?

    Try the test. Stay tuned for the answers.


    Dr. Ron