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engineering
materials science engineering
Questions and Answers of
Materials Science Engineering
List the photolithographic steps necessary to produce a resist mask on a silicon substrate.
Of the two major classifications of photoresists, which type cross-links under exposure to electromagnetic energy of the proper wavelength, resulting in longer polymer chains?
List four requirements of a photoresist.
What were the two most important wavelengths for pho-tolithography provided by the mercury arc lamp?
List the three types of exposure methods used in photolitho¬graphy. Give an advantage of each.
What is undercutting?
What are some possible defects that can result from under-etching? From overetching?
List and describe two properties of etchants.
Compare the three dry etch processes including a description of their etch mechanisms and their advantages.
What are thin films? Why are they important to microelectronic manufacturing?
List two different types of physical vapor deposition including the physical mechanisms and advantages of each.
List three different forms of chemical vapor deposition and indicate in what application each might be used.
What is the key difference in the reactor designs of APCVD and LPCVD processes?
What are the two types of LPCVD reactor designs? List advantages and disadvantages of each.
What is the advantage of using PECVD processes?
What is epitaxy, and why is it important for microelectronic manufacturing?
What is planarization, and why is it needed?
Give three methods for planarizing interconnect layers.
What is electromigration, and why is it a concern in IC processing?
What is the purpose of wafer testing?
Why are clean rooms so important to microelectronic processing?
What two subcomponents make up an IC package?
What are the advantages of surface mount technology and through-hole (or pin-in-hole) technology for attachment of IC packages and discrete electrical components to boards?
Name the four different types of SM lead geometries, and dis¬cuss the advantages of each.
List the key steps involved in conventional IC packaging.
List three techniques for attaching and electrically connecting dies to IC packages.
What is meant by direct chip attachment, and how does it differ from more conventional IC packaging? What are some disadvantages to direct chip attachment?
What are chip-scale packages, and how do they differ from direct chip attachment methods?
What are multichip modules, and why are they advantageous for IC packaging?
What is a printed circuit board (PCB)? What three elements does a PCB consist of?
Name three alternative materials used as dielectrics within PCBs, and give the major reason why each is used.
What is the difference between plated through-holes and via holes?
What is the difference between blind, buried, and through vias?
List the four major process steps for producing a multilayer PCB.
What is the difference between n-type and semiconductors?
List the two methods for inner layer circuitization, and discuss the physical process and advantages of each.
What are built-up mulitlayers and microvias? How are they different from laminates and vias?
List the four major steps for assembling a TH printed wiring assembly (only TH technology).
Why are leads trimmed and clinched after through-hole insertion?
List the four major steps for assembling an SM printed wiring assembly (only SM technology).
Name four methods for feed components to robotic manipulators in pick-and-place robots. Discuss the application of each.
What step in the SM assembly process most strongly affects startup and operations costs for an SM assembly line? Why?
What four zones are necessary within an SM solder reflow thermal profile?
Give three reasons why silicon is the most popular semiconductor used today.
What are some of the factors that influence the cost of making a weldment?
Why is it important to consider welded products as monolithic structures?
How does the fracture resistance and temperature sensitivity of a steel vary with changes in material thickness?
In what way is the weld pool segment of a fusion weld like a small metal casting?
Why is it not uncommon for the selected filler metal to have a chemical composition that is different from the material being welded?
What are some of the defects or problems that can occur in the molten metal region of a fusion weld?
What types of manufacturing processes fall under the classification of consolidation processes?
Why do most welding failures occur in the heat-affected zone?
What are some of the characteristics and consequences of welding with processes that have low rates of heat input?
What are some of the difficulties or limitations encountered in heat treating large, complex welded structures?
What is the purpose of pre- and postheating in welding operations?
What heat-related metallurgical effects may produce adverse results when brazing or soldering?
What are some of the undesirable consequences of residual stresses?
What is the cause of reaction-type residual stresses?
What are some of the techniques that can reduce the amount of distortion in a welded structure?
Residual stresses should not have a harmful effect on load-bearing abilities, except under what conditions?
Why might a welded structure warp if the structure is machined after welding?
What are some of the techniques that can be employed to reduce the likelihood of cracking in a welded structure?
Why are the terms weldability and joinability somewhat nebulous?
What four conditions are required to produce an ideal metallurgical bond?
What are some possible problems associated with the high temperatures that are commonly used in welding?
What is thermal cutting?
What are some of the common types of weld defects?
Through the 1940s the hulls of ocean-going freighters were constructed by riveting plates of steel together. When the defense efforts of World War II demanded accelerated production of freighters to
Two pieces of AISI1025 steel are being shielded-metal-arc welded with E6012 electrodes. Some difficulty is being experienced with cracking in the weld beads and in the heat-affected zones. What
Figure P35-1 schematically depicts the design of a go-cart frame with cross bars and seat support. The assembly is to be constructed from hot-rolled, low-carbon, box-channel material with miter,
Why does an oxyfuel gas welding torch usually have a flame with two distinct regions?
What are some of the more attractive features of the oxyfuel gas process?
In what way does the torch cutting of ferrous metals differ from cutting nonoxidizing metals?
Why might it be possible to cut cast hot steel strands with only an oxygen lance as they emerge from the continuous casting operation?
How does an oxyacetylene cutting torch differ from an oxyacetylene welding torch?
What modification must be incorporated into a cutting torch to permit it to cut metal underwater?
If a curved plate is to be straightened by flame straightening, should the heat be applied to the longer or shorter surface of the arc? Why?
What function or functions are served by the outer zone of the welding flame?
What three types of flames can be produced by varying the oxygen/fuel ratio?
Why might a welder want to change the tip size (or orifice diameter) in an oxyacetylene torch?
What is filler metal, and why might it be needed to produce a joint?
What is the role of a welding flux?
What sorts of problems plagued early attempts to develop arc welding?
What are some of the functions of the gases that form when the electrode coating melts and vaporizes?
What is the function of the slag coating that forms over a shielded metal arc weld?
Why are shielded metal arc electrodes generally limited in length, forcing the process to be one of intermittent operation?
What is the advantage of placing the flux in the center of an electrode (flux-cored arc welding) as opposed to a coating on the outside (shielded metal arc welding)?
What feature enables the welding current in FCAW to be higher than in SMAW?
What are some of the advantages of gas metal arc welding compared to the shielded metal arc process?
Describe the roles of argon, helium, and carbon dioxide gases in creating a high-temperature arc and promoting weld penetration.
Describe the metal transfer that occurs during pulsed arc gas metal arc welding.
What are some of the benefits that can be obtained by the reduced heating of the pulsed arc process?
What are some of the functions of the flux in submerged arc welding?
From a production viewpoint, what are some of the attractive features of submerged arc welding? Major limitations?
What is the primary goal or objective in bulk welding?
What is the function of the ceramic ferrule placed over the end of the stud in stud welding?
What can be done to increase the rate of filler metal deposition during gas tungsten arc welding?
What are some of the attractive features of gas tungsten arc welding?
How are the spot welds produced by gas tungsten arc spot welding different from those made by conventional resistance spot welding?
What is the difference between a consumable and nonconsumable electrode? For which processes does a filler metal have to be added by a separate mechanism?
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