Common Knowledge of Pick and Place Machine and Smt Production

• Generally speaking, the temperature specified in the SMT workshop is 23±7°C;
• Materials and tools required for solder paste printing: solder paste, steel plate, scraper, wiping paper, dust-free paper, cleaning agent, mixing knife;
• The commonly used solder paste composition is Sn96.5%/Ag3%/Cu0.5%;
• The main components of solder paste are divided into two parts: tin powder and flux;
• The main function of flux in soldering is to remove oxides, destroy the surface tension of molten tin, and prevent re-oxidation;
• The volume ratio of tin powder particles and Flux (flux) in solder paste is about 1:1, and the weight ratio is about 9:1;
• The principle of taking solder paste is first in first out;
• When the solder paste is unpacked and used, it must go through two important processes of warming up and stirring;
• The common production methods of steel plates are: etching, laser, electroforming;
• The full name of SMT is Surface mount (or mounting) technology, which means surface adhesion (or mounting) technology in Chinese;
• The full name of ESD is Electro-static discharge, which means electrostatic discharge in Chinese;
• When making an SMT equipment program, the program includes five parts, which are PCB data; Mark data; Feeder data; Nozzle data; Part data;
• The melting point of lead-free solder Sn/Ag/Cu 96.5/3.0/0.5 is 217℃;
• The control relative temperature and humidity of the parts drying box is < 10%;
• Commonly used passive components (PassiveDevices) include: resistors, capacitors, inductors (or diodes), etc.; active components (ActiveDevices) include: transistors, ICs, etc.;
• The commonly used SMT steel plate is made of stainless steel;
• The thickness of the commonly used SMT steel plate is 0.15mm (or 0.12mm);
• The types of electrostatic charge include friction, separation, induction, electrostatic conduction, etc.; the impact of electrostatic charge on the electronics industry is: ESD failure, electrostatic pollution; the three principles of static electricity elimination are electrostatic neutralization, grounding, and shielding;
• Inch size length x width 0603=0.06inch*0.03inch, metric size length x width 3216=3.2mm*1.6mm;
• The full name of ECN in Chinese is: Engineering Change Notice; the full name of SWR in Chinese is: Special Requirements Work Order, which must be countersigned by relevant departments and distributed by the document center to be valid;
• The purpose of PCB vacuum packaging is to prevent dust and moisture;
• The quality policy is: comprehensive quality control, implementing the system, and providing the quality required by customers; full participation, timely processing, to achieve the goal of zero defects;
• The three-no quality policy is: do not accept defective products, do not manufacture defective products, and do not export defective products;
• The ingredients of solder paste include: metal powder, solvent, flux, anti-sagging agent, and active agent; by weight, metal powder accounts for 85-92%, and by volume metal powder accounts for 50%;
• Solder paste must be taken out of the refrigerator to return to temperature when used. The purpose is to restore the temperature of the refrigerated solder paste to normal temperature for printing. If the temperature is not returned, the defect that is likely to occur after the PCBA enters the Reflow is tin beads;
• SMT PCB positioning methods include: vacuum positioning, mechanical hole positioning, bilateral clamp positioning and board edge positioning;
• The resistor whose silk screen (symbol) is 272 has a resistance value of 2700Ω, and the symbol (silk screen) of a resistor with a resistance value of 4.8MΩ is 485;
• CPK refers to: the process capability under the current actual situation;
• The flux starts to volatilize in the constant temperature zone for chemical cleaning;
• Rosin-based flux can be divided into four types: R, RA, RSA, RMA;
• The RSS curve is heating→constant temperature→reflux→cooling curve;
• The PCB material we are using is FR-4;
• The PCB warpage specification does not exceed 0.7% of its diagonal;
• At present, the BGA ball diameter commonly used on computer motherboards is 0.76mm;
• The ABS system is an absolute coordinate;
• The error of ceramic chip capacitor ECA-0105Y-K31 is ±10%;
• The PCB of the computer currently in use is made of: glass fiber board;
• The diameter of tape and reel for SMT parts packaging is 13 inches and 7 inches;
• The opening of the SMT general steel plate is 4um smaller than that of the PCB PAD to prevent the phenomenon of bad solder balls;
• According to the "PCBA Inspection Specification", when the dihedral angle > 90 degrees, it means that the solder paste has no adhesion to the wave soldering body;
• After the IC is unpacked, the humidity on the display card is greater than 30%, indicating that the IC is damp and absorbs moisture;
• The weight ratio and volume ratio of tin powder and flux in the solder paste composition are correct 90%:10%, 50%:50%;
• The early surface mount technology originated from the military and avionics fields in the mid-1960s;
• At present, the contents of Sn and Pb in the most commonly used solder paste for SMT are: 63Sn 37Pb; the eutectic point is 183°C;
• The feeding distance of the common paper tape tray with a bandwidth of 8mm is 4mm;
• The most widely used electronic component material in SMT is ceramics;
• The temperature curve of the reflow furnace is most suitable for the maximum temperature of the curve at 215C;
• During the tin furnace inspection, the temperature of the tin furnace is 245°C;
• The opening pattern of the steel plate is square, triangle, circle, star, and epitome;
• The solder paste currently on the market actually only has a sticking time of 4 hours;
• The rated air pressure generally used by SMT equipment is 5KG/cm2;
• Tools for SMT parts maintenance include: soldering iron, hot air extractor, tin suction gun, tweezers;
• The high-speed pick and place machine can mount resistors, capacitors, ICs, and transistors; the packaging methods are Reel and Tray, and Tube is not suitable for high-speed pick and place machines;
• The characteristics of static electricity: small current, greatly affected by humidity;
• What kind of welding method is used when the front PTH and the back SMT pass through the tin furnace;
• Common inspection methods for SMT: visual inspection, X-ray inspection, machine vision inspection;
• The heat conduction mode of ferrochrome repair parts is conduction convection;
• At present, the main components of solder balls in BGA materials are Sn90 Pb10, SAC305, SAC405;
• Laser cutting, electroforming, and chemical etching of steel plates;
• The temperature of the welding furnace is pressed: use the temperature detector to measure the applicable temperature;
• When the SMT semi-finished products of the welding furnace are exported, the welding status is that the parts are fixed on the PCB;
• The history of modern quality management development TQC-TQA-TQM;
• The ICT test is a bed of needles test;
• ICT testing can test electronic components using static testing;
• The characteristics of solder are that the melting point is lower than other metals, the physical properties meet the welding conditions, and the fluidity at low temperature is better than other metals;
• The measurement curve must be re-measured when the welding furnace parts are replaced and the process conditions are changed;
• The solder paste thickness gauge uses Laser to measure: solder paste thickness, solder paste thickness, and printed width of solder paste;
• The feeding methods of SMT parts include vibrating feeder, disc feeder and tape feeder;
• Which mechanisms are used in SMT equipment: cam mechanism, side rod mechanism, screw mechanism, sliding mechanism;
• If the packaging method of the parts is 12w8P, the size of the counter Pinth must be adjusted by 8mm each time;
• Types of welding machines: hot air welding furnace, nitrogen welding furnace, laser welding furnace, infrared welding furnace;
• Methods that can be used for SMT parts sample trial production: streamline production, hand-printed machine placement, hand-printed hand-mounted;
• Commonly used MARK shapes are: circle, "ten" shape, square, rhombus, triangle, swastika;
• Due to improper setting of Reflow Profile in the SMT section, it is the preheating zone and cooling zone that may cause microcracks of the parts;
• Uneven heating at both ends of the SMT part is easy to cause: empty welding, deviation, tombstone;
• The cycle time of the high-speed running machine and the pick and place machine should be balanced as much as possible;
• The pick and place machine should paste small parts first, and then paste large parts;
• SMT parts can be divided into two types: LEAD and LEADLESS according to whether there are parts or not;
• There are three basic types of common automatic pick and place machines, continuous placement type, continuous placement type and mass transfer pick and place machine;
• It can be produced without LOADER in the SMT process;
• The SMT process is a board feeding system-solder paste printing machine-high-speed running machine-pick and place machine-reflow soldering-board receiving machine;
• Reasons for short circuit caused by poor printing in the manufacturing process:

          Insufficient metal content of solder paste, resulting in collapse

          Excessive opening of the steel plate, resulting in excessive tin content

          Poor quality of steel plate, poor tin application, change the laser cutting template

   There is solder paste on the back of the stencil, reduce the pressure of the scraper, and use appropriate VACUUM and SOLVENT;

• The main engineering purpose of each area of the general reflow furnace Profile:

          Preheating area; engineering purpose: solvent volatilization in solder paste.

   Uniform temperature zone; engineering purpose: activation of flux, removal of oxides; evaporation of excess water.

          Reflow area; engineering purpose: solder melting.

  Cooling area; engineering purpose: alloy solder joints are formed, part feet and pads are connected as one;

• In the SMT process, the main reasons for solder balls are: poor design of PCB PAD, poor design of steel plate openings, excessive placement depth or pressure, excessive rising slope of Profile curve, collapse of solder paste, and low viscosity of solder paste .

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