National Unit Specification: General Information

Transcription

1 National Unit Specification: General Information NUMBER D00R 11 COURSE SUMMARY Explaining the principles applicable to the safe installation and removal of surface mount devices. OUTCOMES 1 Identify a range of surface mount devices. 2 Identify the types of solder and flux used in electronics and their applications. 3 Explain the basic principles of heat transfer in the soldering process. 4 Identify acceptability criteria for surface mount device positioning and quality of solder joints. 5 Explain electrostatic discharge control. RECOMMENDED ENTRY Some experience in soldering and a knowledge of electronic components would be an advantage such as achievement of NC module Electronic Components and Circuit Assembly Techniques. CREDIT VALUE 1 Credit at Intermediate 2 CORE SKILLS Information on the automatic certification of any core skills in this unit is published in Automatic Certification of Core Skills in National Qualifications (SQA, 1999). Administrative Information Superclass: XL Publication date: December 1998 Source: Scottish Qualifications Authority Version: 01 Scottish Qualifications Authority 1999 This publication may be reproduced in whole or in part for education purposes provided that no profit is derived from reproduction and that, if reproduced in part, the source is acknowledged. Additional copies of this specification can be purchased from the Scottish Qualifications Authority. The cost is (minimum charge 5.00).

2 National unit specification: statement of standards Acceptable performance in this unit will be the satisfactory achievement of the standards set out in this part of the unit specification. All sections of the statement of standards are mandatory and cannot be altered without reference to the Scottish Qualifications Authority. OUTCOME 1 Identify a range of surface mount devices. a) Chip component types and their codes and markings are identified correctly. b) A range of transistor and pin configurations are identified correctly. c) A range of integrated circuit packages and pin configurations are identified correctly. Surface mount devices should include: chip resistors and capacitors; MELF s; SOT s; SOIC s; PLCC s; QFP s including finepitch. Performance evidence that the candidate can identify the range of device types, codings and markings and pin configurations. OUTCOME 2 Identify the types of solder and flux used in electronics and their applications. a) A range of wire solder and solder paste are stated correctly. b) A range of flux types used in electronics is identified correctly. c) The applications for wire solder and solder paste are stated correctly. d) The role of flux in the soldering process is stated correctly. e) The applications for a range of flux types are described correctly. f) The health and safety requirements when working with solder and flux are identified correctly. Solder types: 60/40; 62/36/2. Flux types: rosin; no clean; water soluble. Health and Safety: fume extraction; material handling and storage. Performance evidence that the candidate can state a range of solder and flux types, state applications where they can be used and provide oral/written evidence stating health and safety requirements when working with solder and flux.

3 National unit specification: statement of standards (cont) OUTCOME 3 Explain the basic principles of heat transfer in the soldering process. a) The methods of heat transfer in the soldering process are explained correctly. b) The factors controlling heat at the solder joint are explained correctly. Methods of heat transfer: conductive; convective; forced air. Oral/written evidence that the candidate can explain methods of heat transfer and factors which control heat at the solder joint. OUTCOME 4 Identify acceptability criteria for surface mount device positioning and quality of solder joints. a) The acceptability criteria for positioning of surface mount devices are identified correctly. b) The acceptability criteria for quality of solder joints are identified correctly. c) A range of solder defects are identified correctly. d) The role of cleaning solvents is stated correctly. e) The safety aspects of cleaning solvents are stated correctly. Device types: chip components; MELF s; SOT s; SOIC s; PLCC s; QFP s. Performance evidence that the candidate can identify for the range of surface mount devices acceptable positioning, quality of solder joints and solder defects. Written/oral evidence stating the role of cleaning solvents and the safety aspects. OUTCOME 5 Explain electrostatic discharge control. a) The meaning of electrostatic discharge is correctly explained. b) The reason why electrostatic discharge needs to be controlled is correctly explained. c) The sources of static charges are correctly described.

4 National unit specification: statement of standards (cont) d) The methods used in preventing electrostatic discharge are described correctly. Methods used in preventing electrostatic discharge: wrist straps; bench mats; grounded solder stations; component storage; clothing. Oral/ written evidence that the candidate can state the meaning of ESD, why it needs to be controlled, and the sources of static and methods of prevention.

5 National unit specification: support notes This part of the unit specification is offered as guidance. None of the sections of the support notes is mandatory. GUIDANCE ON CONTENT AND CONTEXT The content required for each outcome is listed below: 1 Surface mount devices to be identified should include: chip resistors, chip capacitors, MELF s, SOT s, SOIC s, PLCC s and QFP s. Resistor and capacitor size codes and the method of indicating the device value ie colour code, numerical value code. SOT s SOIC s PLCC s QFP s 208, QFP-256. A range of small outline transistor packages and the methods of identifying pin configuration eg SOT-23, SOT-89, SOT-143. A range of small outline integrated circuit packages and the methods of identifying pin configurations eg SOIC-14, SOIC-16, SOIC-20. A range of plastic leaded chip carrier packages and the methods of identifying pin configurations eg PLCC-20, PLCC-44, PLCC-68, PLCC-84. A range of quad flat packs including fine pitch devices and the methods of identifying pin configurations eg QFP-80, QFP-100, QFP- 2 SOLDER solder packaging forms ie wire solder, solder paste composition of solder solder melting points, eutectic solder applications for different composition solders health and safety requirements: fume extraction systems. FLUX purpose of flux, types of flux, eg rosin, no clean, water soluble activating temperatures flux residues health and safety requirements: fume extraction systems; handling and storage of flux used in electronic soldering. 3 Heat transfer methods: conductive ie soldering iron; convective ie forced hot air Conductive direct heating Convective non-contact heating Heat control factors; size of handpiece tip, temperature of tip, size of component, type of circuit board, adjacent components, source of heat.

6 National unit specification: support notes (cont) 4 Component positioning standards Solder joint standards Solder defects eg icicles, solder bridges, solder balls, dry joints, blow holes. Cleaning solvents: to remove contaminants from components and circuit boards, health and safety requirements regarding cleaning solvents. 5 Components that are sensitive to ESD. Sources of static charge, methods of prevention: wrist straps; bench mats; grounded solder stations; component storage; component handling; clothing; footwear; tools; PCB storage. Damage to devices can be catastrophic or degrade performance with a subsequent effect on equipment reliability. The unit is intended to provide underpinning knowledge which will allow the candidate to gain a better understanding of the processes involved with the safe installation and removal of surface mount devices. The main areas of study are the devices, solder and flux, methods and factors in the heating process during soldering, quality standards regarding the positioning and soldering of the devices and the health and safety aspects that have to be considered during the rework process. This unit would be best delivered in conjunction with D00S 11 Surface Mount Technology Rework Practice. GUIDANCE ON TEACHING AND LEARNING APPROACHES Every opportunity should be taken to ensure that the learning and teaching contexts are to the current industry standards and are relevant to the candidate. The unit should be delivered in a suitable workshop environment. It is intended to be practical hands on with each candidate given the opportunity to gain experience in the range of surface mount devices, solder and flux types and equipment used to control static discharge. Device identification could be supported with suitably populated PCB s. The PCB could also be used to demonstrate the criteria for quality of solder joints and acceptable device positioning.

7 National unit specification: support notes (cont) GUIDANCE ON APPROACHES TO ASSESSMENT Outcomes 1 and 4 An observation checklist could be kept by the tutor as evidence of candidates completing practical assignments successfully. A written test could be used to assess the content statement for each performance criteria. Candidates should be allowed manufacturers data sheets and relevant industry Standards. Outcomes 2, 3 and 5 A written test could be used to assess knowledge and understanding of the content statement for each performance criteria. This test should be closed book with the lecturer in attendance to ensure examination conditions within the classroom. Advice on Generating Evidence Candidates should be encouraged to complete assignments and other tasks in an independent manner. Outcomes 1 and 4 Suitably populated PCB s could be provided from which the candidate could: identify the range of surface mount devices identify acceptability criteria for SMD positioning for the range of devices identify acceptability criteria for quality of solder joints for the range of devices An observational checklist could be kept by the tutor as evidence of candidates completing practical assignments successfully. In addition, the candidate could provide written evidence of component identification from manufacturers data sheets with the criteria for device positioning and solder joint quality obtained from British or IPC Standards. Outcome 2 The candidates could be given a series of practical assignments allowing them to identify a range of solder and flux. An observational checklist could be kept by the tutor as evidence of candidates completing practical assignments successfully.

8 National unit specification: support notes (cont) Written evidence giving applications for solder and flux in electronics. In addition, the candidate could provide written evidence as to the role of flux in the soldering process. Written evidence of the need for fume extraction when carrying out electronics soldering. Outcomes 3 and 5 A written test could be used to assess knowledge and understanding as indicated in the content statements of the performance criteria. This test should be closed book with the lecturer in attendance to ensure examination conditions within the classroom. SPECIAL NEEDS This unit specification is intended to ensure that there are no artificial barriers to learning or assessment. Special needs of individual candidates should be taken into account when planning learning experiences, selecting assessment instruments or considering alternative outcomes for units. For information on these, please refer to the SQA document Guidance on Special Assessment and Certification Arrangements (SQA, 1998).