110 knowledge points of SMT chip processing part 2
56. In the early 1970s, there was a new type of SMD in the industry, which was called “sealed foot less chip carrier”, which was often replaced by HCC;
57. The resistance of the module with symbol 272 should be 2.7K ohm;
58. The capacity of 100nF module is the same as that of 0.10uf;
The eutectic point of 63Sn + 37Pb is 183 ℃;
60. The most widely used raw material of SMT is ceramics;
61. The highest temperature of the reflow furnace temperature curve is 215C;
62. The temperature of the tin furnace is 245c when it is inspected;
63. For SMT parts, the diameter of coiling plate is 13 inches and 7 inches;
64. The opening type of the steel plate is square, triangular, round, star shaped and plain;
65. Currently used computer side PCB, its raw material is: glass fiber board;
66. What kind of substrate ceramic plate is the solder paste of sn62pb36ag2 to be used;
67. Rosin based flux can be divided into four types: R, RA, RSA and RMA;
68. Whether the resistance of SMT section is directional or not;
69. The current solder paste on the market only needs 4 hours of sticky time in practice;
70. The additional air pressure normally used by SMT equipment is 5kg / cm2;
71. What kind of welding method should be used when PTH on the front side does not pass through the tin furnace with SMT;
72. Common inspection methods of SMT: visual inspection, X-ray inspection and machine vision inspection
73. The heat conduction method of ferrochrome repair parts is conduction + convection;
74. According to current BGA data, sn90 pb10 is the primary tin ball;
75. Manufacturing method of steel plate: laser cutting, electroforming and chemical etching;
76. The temperature of the welding furnace: use a thermometer to measure the applicable temperature;
77. When the SMT SMT semi-finished products are exported, the parts are fixed on the PCB;
78. Process of modern quality management tqc-tqa-tqm;
79. ICT test is needle bed test;
80. ICT test can be used to test electronic parts, and static test is selected;
81. The characteristics of soldering tin are that the melting point is lower than other metals, the physical properties are satisfactory, and the fluidity is better than other metals at low temperature;
82. The measurement curve should be measured from the beginning when the process conditions of welding furnace parts are changed;
83. Siemens 80F / S belongs to electronic control drive;
84. The solder paste thickness gauge uses laser light to measure: solder paste degree, solder paste thickness and solder paste printing width;
85. SMT parts are supplied by oscillating feeder, disc feeder and coiling belt feeder;
86. Which organizations are used in SMT equipment: cam structure, side bar structure, screw structure and sliding structure;
87. If the visual inspection section cannot be recognized, the BOM, manufacturer approval and sample board shall be followed;
88. If the packing method of parts is 12w8p, the pinth scale of counter must be adjusted to 8mm each time;
89. Types of welding machines: hot air welding furnace, nitrogen welding furnace, laser welding furnace and infrared welding furnace;
90. Available methods for SMT parts sample trial: streamline production, hand printing machine mounting and hand printing hand mounting;
91. The commonly used mark shapes are: circle, cross, square, diamond, triangle, Wanzi;
92. Because the reflow profile is not set properly in SMT section, it is the preheating zone and cooling zone that can form the micro crack of the parts;
93. The two ends of SMT parts are heated unevenly and easy to form: empty welding, deviation and stone tablet;
94. SMT parts repair things are: soldering iron, hot air extractor, tin gun, tweezers;
95. QC is divided into IQC, IPQC,. FQC and OQC;
96. High speed Mounter can mount resistor, capacitor, IC and transistor;
97. Characteristics of static electricity: small current and great influence by humidity;
98. The cycle time of high-speed machine and universal machine should be balanced as far as possible;
99. The true meaning of quality is to do well in the first time;
100. The placement machine should stick small parts first and then large parts;
101. BIOS is a basic input / output system;
102. SMT parts can be divided into lead and leadless according to whether there are feet;
103. There are three basic types of active placement machines: continuous placement, continuous placement and many hand over placers;
104. SMT can be produced without loader;
105. The SMT process consists of feeding system, solder paste printer, high speed machine, universal machine, current welding and plate collecting machine;
106. When the temperature and humidity sensitive parts are opened, the color in the humidity card circle is blue, and the parts can be used;
107. The dimension standard of 20 mm is not the width of strip;
108. Causes of short circuit due to poor printing in the process:
a. If the metal content of solder paste is not good, it will cause collapse
b. If the opening of the steel plate is too large, the tin content is too much
c. If the quality of the steel plate is poor and the tin is poor, replace the laser cutting template
D. there is residual solder paste on the reverse side of stencil, reduce the pressure of scraper, and select appropriate vaccum and solvent
109. The primary engineering intent of each zone of the profile of the reflow furnace is as follows:
a. Preheat zone; engineering intention: flux transpiration in solder paste.
b. Temperature equalization zone; engineering intent: flux activation to remove oxides; transpiration of residual moisture.
c. Reflow zone; engineering intent: solder melting.
d. Cooling zone; engineering intention: alloy solder joint composition, part foot and pad as a whole;
110. In SMT SMT process, the main causes of solder bead are: poor depiction of PCB pad, poor depiction of steel plate opening, excessive depth or pressure of placement, too large rising slope of profile curve, solder paste collapse and low paste viscosity.
Post time: Sep-29-2020