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3 types of Conformal Coating: Acrylic Resin (AR) Correct Answer This type of coating provides FAIR elasticity and general protection. It has high dielectric strength, and fair moisture and abrasion resistance. This coating is different from others because its facility for removal. This type are EASILY and quickly removed by a variety of solvents, often without requiring agitation. This makes rework and field repair very practical and economical. This type doesn't protect against solvents and solvent vapors. 3 types of Conformal Coating: Silicone Resin (SR) Correct Answer This type of coating provides EXCELLENT protection in a very wide temperature range. This coating provides good chemical resistance, moisture, and salt spray resistance, and is very flexible. This type is NOT abrasion resistant because of its rubbery nature, but this property does make it resilient against vibrational stresses. Commonly used in high-humidity environments. Removal can be CHALLENGING. requiring specialized solvents, long soak time, and agitation from a brush. 3 types of Conformal Coating: Urethane (Polyurethane) Resin (UR) Correct Answer This type of coating is known for its EXCELLENT moisture and chemical resistance. It is
also very abrasion resistant. Combining those factors with its SOLVENT RESISTANCE results in a conformal coating that is very difficult to remove. Like SR, full removal generally requires special solvents, long soak time, and agitation with a brush. This is common in aerospace application. ex: Conathane 5 Coating application methods: Manual Spraying Correct Answer Aerosol can or handheld spray gun. Time consuming method of coating for a small quantity of boards. Lots of masking beforehand. Quality and consistency of outcome are operator- dependent. 5 Coating application methods: Automated spraying Correct Answer Programmed spray system that moves the board on a CONVEYOR under an alternative spray head that applies a conformal coating. 5 Coating application methods: Selective coating Correct Answer An automated conformal coating process that uses PROGRAMMABLE ROBOTIC SPRAY NOZZLES to apply the coating to very specific areas on the circuit board. May eliminate the need for masking using the program. The UV lamp in machine helps cure the coating right after it is sprayed. 5 Coating application methods: Dipping Correct Answer The circuit board is first immersed, Then withdrawn from the conformal coating solution. Immersion speed, withdrawn speed, Immersion time, and Viscosity determine the resulting film formation. Common for high
Causes: - coating is too thick
- thermal shock
- coating cured too quickly (6) Most Common Coating Defects and causes: Dewetting Correct Answer Coating will not evenly coat the surface to which its applied. Causes: - uneven coating application.
- improper mixture of two- part material.
- Residue on coating surface.
- Surface tension and surface energy. (6) Most Common Coating Defects and causes: Delamination Correct Answer When coating has lifted up and away from the board. This hinders protection because the area below the coating is left exposed. (Ex:Ripping off more coating after demasking and pulling off too much coating around the area. Causes:
- too thick of coating
- coating not adhering to previous coating layer.
- contamination of surface of the board. (6) Most Common Coating Defects and causes: Orange Peel Correct Answer Coating appears dull, resembling the skin of a fruit or basketball. Causes:
- substrate is too hot.
- improper mixture of solvent and coating ratio.
- environment is too dry during application.
- Second coat has been applied before the first coat is dry. (6) Most Common Coating Defects and causes: Air Bubbles, Pinholes, and Foam Correct Answer Bubbles occur when pockets of air get trapped under a conformal coating layer. Foam is an extreme form of bubbling, and sometimes bubbles burst through the coating, forming a pinhole. Causes:
- coating is too viscous.
- The coating is too thick.
- application equipment not setup properly. What is the purpose of Conformal Coating? Correct Answer Conformal coatings can be used in a wide range of environments to protect printed circuit boards from moisture, salt spray, chemicals and temperature extremes in order to prevent such things as corrosion, mold growth, and electrical failures. Measuring wet coating (2) Wet Film Comb Correct Answer Most common method to measure wet coating. The gauge consists of a series of combs with different distance between the marked points and the baseline. After placing the comb into the wet coating film, the thickness can be measured in Microns or Mils. Measurement determined by the number between the last tooth coated and the following tooth which is free of coating. Measuring wet coating (2)
conductive foil or any other planar separation within a printed board. Weave Texture Correct Answer Surface condition of a base material in which a weave pattern of glass cloth is apparent although the unbroken fibers are completely covered with resin. Weave Exposure Correct Answer Surface condition of a base material in which the unbroken fibers of woven glass cloth are NOT completely covered by resin. Haloing Correct Answer condition existing in the base material in the form of a light area around holes or other machined areas on or below the surface of the base material. Mechanically induced fracturing or delamination on or below the surface of the base material; a Light area around the holes, other machined areas or both. (a light ring around a hole on a circuit board) FOD (Foreign Object Debris) Correct Answer A generic term for a substance, debris, particulate matter or article alien to the assembly or system. ex: wire and lead clippings, hair, dust, non-ESD safe objects. Solder Mask Coating Correct Answer Heat-resisting coating material applied to selected areas to prevent the deposition of solder upon those areas during subsequent soldering. Solder Mask material may be applied as a liquid or a dry film. (ex: pink masking)
Conformal Coating Correct Answer Provides a barrier layer to the surface of an electronic assembly to provide protection against the end use environment.
- distribution depends partly on the method of application and may affect visual appearance and corner coverage. Dipping Correct Answer May have a drip line or localized build-up on the edge of the board. This build-up may contain small amount of bubbles but it will not affect the functionality or reliability of the coating. Electrostatic Discharge (ESD) Correct Answer The rapid transfer of a static electric charge from one object to another at a different electrical potential. Electrostatic Discharge Sensitive (ESDS) Correct Answer Components and assemblies are damaged by these electrical energy surges.
- ESDS components can fail to operate, or may change in value due to improper handling or processing.
- immediate failures usually require replacement of the component. Classification: Class 1,2, Class 1 (General Electronic Products) Correct Answer Type of classification that includes products suitable for applications where the major requirement is FUNCTION of the assembly. Classification: Class 1,2,
Non-Wetting Correct Answer The inability of molten solder to form a metallic bond with the basis metal. Class 1 Product Correct Answer General Electronics Product - includes products where the major requirement is function of the completed assembly. Class 2 Product Correct Answer Dedicated Service Electronic Product - Continued performance and extended life required. Uninterrupted service is desired but not required. Class 3 Product Correct Answer High Performance Electrical Product - Continued high performance or performance-on-demand is critical. Equipment downtime cannot be tolerated. Equipment might be used for life- support or other critical systems. Who as the ultimate responsibility for identifying the class to which the assembly is evaluated? Correct Answer The Customer. Shall Correct Answer Invokes a requirement for manufacturers of all classes or product, and failure to comply with the requirement is a noncompliance to this standard. Order of Precedence in event of conflict 1 Correct Answer
- Procurement as agreed and documented between customer and supplier.
Order of Precedence in event of conflict 2 Correct Answer Master drawing or master ass. drawing reflecting the customer's detailed requirements. Order of Precedence in event of conflict 3 Correct Answer IPC- 1 - 610 when invoked by the customer or contract. If documents other than IPC-A-610 are cited, the order of precedence shall be defined in the _ Correct Answer Procurement documents Target Condition Correct Answer A condition that is close to perfect, but is not always achievable and may not be necessary to ensure the reliability of the assembly. Acceptable Condition Correct Answer A condition that, while not necessarily perfect, will maintain integrity and reliability of the assembly Defect Condition Correct Answer The form, fit or function of the assembly is inadequate for use in its end use environment. A defect for Class 1... Correct Answer automatically implies a defect for Class 2 and 3. A defect for Class 2 implies a defect for Class 3. Disposition Correct Answer The determination of how defects should be treated. These include rework, use as is, scrap, and repair.
Solder source side Correct Answer The side of the PCB to which solder is applied. This is usually the secondary side, but might be the primary side in some cases. Solder Destination Side Correct Answer The side of the PCB that the solder flows toward in through-hole technology. The destination is is normally the primary side of the PCB, but might be the secondary side in some cases. Cold Solder Connection Correct Answer A solder connection that exhibits poor wetting and that is characterized by a grayish porous appearance. What can cause a cold solder connection? Correct Answer Excessive impurities in the solder, inadequate cleaning prior to the soldering, and/or insufficient application of heat during the soldering process. Any violation of minimal electrical clearance is a... Correct Answer defect condition for all classes. Meniscus (component) Correct Answer Sealant or encapsulant on a lead, protruding from the seating plane of the component. This includes ceramic, epoxy or other composites, and flash from molded components. Nonfunctional Land Correct Answer A land that is not connected electrically to the conductive pattern on its layer.
Wire OverWRAP Correct Answer A wire/lead that is wrapped more than 360 degrees and remains in contact with the terminal post. Wire OverLAP Correct Answer A wire/lead is wrapped more than 360 degrees and crosses over itself (and does not remain in contact with the terminal post). Examples and illustrations... Correct Answer are often grossly exaggerated in order to depict the reasons for this classification. Inspection Methodology Correct Answer The inspector does not select the class for the assembly under inspection. Verification of Dimensions Correct Answer The actual measurements provided in this document (i.e., specific part mountings and solder fillet dimensions and determination of percentages) are not required except for referee purposes. The tolerance for magnification aides is... Correct Answer +/- 15% of the selected magnification power. Illumination at the surface of workstations should be at least _ Correct Answer 1000lm/m2 [approximately 93 foot candles]. Light sources should be selected to prevent _. Correct Answer shadows
What are typical contaminants that might cause soldering and coating problems? Correct Answer Body salts and oils, and unauthorized hand creams. What should be done to prevent ESD and EOS damage to sensitive components? Correct Answer All handling, unpacking and assembly shall be performed at a static- controlled workstation. Lane width or land diameter of >=.25 to <=.5mm will have a ... Correct Answer magnification power inspection range of 7.5x to 10x and a maximum referee of 20x. A main goal of the IPC Professional Training and Certification Programs is to... Correct Answer provide an understanding of accept/reject criteria to enhance an individual's ability and motivation to consistently and correctly apply the technical discrimination criteria. How long are IPC certs good for? Correct Answer Master IPC Trainer, Certified IPC Trainer, and Certified IPC Specialist certifications expire after two years. Certification is valid through the last day of the month, regardless of the day of the month the certification was granted. IPC Certifications are personal and portable credentials... Correct Answer granted to individuals, not the employing company. Certifications are personal property and are retained when changing employment.
Certified IPC Specialist recertification may be provided by... Correct Answer any Master IPC Trainer or Certified IPC Trainer. Certified IPC Trainers are authorized to grant a single extension of _ days to a certified IPC specialist. Such exceptions should be noted on the certification document. Correct Answer 90 What does a certified IPC specialist training program accomplish? Correct Answer Certified IPC Specialist training programs will train, test and certify in the correct application of the criteria for all product classes. Materials authorized for reproduction by the user will be so identified and provided by IPC in ____ format, e.g. student training materials (previously called student handbooks) Correct Answer electronic An applicant who completes the training course but fails to pass the certification measurement criteria can retest not sooner than 24 hours nor more than _ days following the original testing, except as authorized in writing by IPC's director of certification. Correct Answer 90
