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PCBA Tech
57 questions you must know about SMT patch
PCBA Tech
57 questions you must know about SMT patch

57 questions you must know about SMT patch

2021-11-10
View:34
Author:Downs

  The ideal mirror image relationship between the cooling zone curve and the reflux zone curve;

  RSS curve is heating → constant temperature → reflux → cooling curve;

   The PCB material currently used is FR-4;

   PCB warpage specification does not exceed 0.7% of its diagonal;

   STENCIL laser cutting is a method that can be reworked;

  The diameter of the BGA ball commonly used on computer motherboards is 0.76mm;

  ABS system is absolute coordinates;

   The error of ceramic chip capacitor ECA-0105Y-K31 is ±10%;

   Panasert Panasonic automatic placement machine has a voltage of 3~200±10VAC;

   SMT parts packaging, its tape-and-reel diameter is 13 inches, 7 inches;

   SMT general steel plate opening is 4um smaller than PCB PAD to prevent bad solder balls;

pcb board

   According to the "PCBA Inspection Regulations", when the dihedral angle is greater than 90 degrees, it means that the solder paste has no adhesion to the wave solder body;

   After the IC is unpacked, if the humidity on the humidity display card is greater than 30%, it means that the IC is damp and absorbing;

   The correct weight ratio and volume ratio of tin powder to flux in the solder paste ingredients are 90%:10%, 50%:50%;

   The early surface bonding technology originated from the military and avionics fields in the mid-1960s;

   The contents of Sn and Pb in the solder paste most commonly used in SMT are: 63Sn+37Pb;

   The feeding distance of the common paper tape tray with a width of 8mm is 4mm;

  In the early 1970s, a new type of SMD in the industry was a "sealed footless chip carrier", often replaced by HCC;

   The resistance value of the component with symbol 272 should be 2.7K ohms;

  The capacitance value of the 100NF component is the same as 0.10uf;

   The eutectic point of 63Sn+37Pb is 183℃;

   The most used electronic component material for SMT is ceramic;

  The temperature curve of the reflow furnace is the most suitable for its maximum temperature of 215C;

   During tin furnace inspection, the temperature of the tin furnace is 245C;

 SMT parts are packaged with a tape-and-reel reel with a diameter of 13 inches and 7 inches;

   The hole pattern of the steel plate is square, triangle, round, star, and original shape;

   The computer-side PCB currently in use is made of glass fiber board;

   Sn62Pb36Ag2 solder paste is mainly used for what kind of substrate ceramic board;

   Rosin-based flux can be divided into four types: R, RA, RSA, RMA

   SMT segment exclusion with or without directionality;

  The solder paste currently on the market has only 4 hours of tack time;

   The rated air pressure of 7SMT equipment is generally 5KG/cm2;

. SMT equipment generally uses rated air pressure of 5KG/cm2;

   PTH on the front and SMT on the back, which welding method is used when passing through the tin furnace;

 SMT common inspection methods: visual inspection, X-ray inspection, machine vision inspection

   The heat conduction method of ferrochrome repair parts is conduction + convection;

   At present, the solder balls of BGA materials are mainly Sn90 Pb10;

  Steel plate production method: laser cutting, electroforming, chemical etching;

  The temperature of the arc welding furnace is as follows: Use a thermometer to measure the applicable temperature;

  The SMT semi-finished products of the recirculation welding furnace are in the welding condition that the parts are fixed on the PCB when they are exported;

   The development course of modern quality management TQC-TQA-TQM;

   ICT test is a needle bed test;

ICT test can test electronic parts using static test;

   The characteristics of soldering tin are that the melting point is lower than that of other metals, the physical properties meet the welding conditions, and the fluidity at low temperatures is better than other metals;

  The replacement process conditions of the parts of the arc welding furnace need to re-measure the measurement curve;

   Siemens 80F/S is a relatively electronic control drive;

   The solder paste thickness gauge uses Laser light to measure: solder paste degree, solder paste thickness, solder paste printing width;

   SMT parts feeding methods include vibrating feeder, disc feeder, tape feeder;

   Which mechanisms are used in SMT equipment: cam mechanism, side lever mechanism, screw mechanism, sliding mechanism