Rigao Pcba Specialized in Turn-Key Electronics, pcb printed circuit boards manufacturing Since 2006.

A, preparing a PCB assembly welding good actual product surface board

by:Rigao      2020-04-03
Because good solder paste printing, no welding assembling PCB board can't fixed thermocouple test, so you need to use the welded actual product for testing. In addition, the test sample cannot be used repeatedly, not more than 2 times. In general, as long as the test temperature does not exceed the limit temperature of test 1 ~ 2 times of assembled plate can also be used as a formal product, but absolutely do not allow the long-term repeated use of the same test sample for testing. Over a long period of time because of the high temperature of welding, the color of the PCB will be deep, and even become brown brown. Although the hot blast stove heating mode is mainly conduction, convection but there is also a small amount of radiation, conduction, dark brown than normal fresh light green PCB to absorb more calories. Therefore, the measured temperature is higher than the actual temperature. If, in the lead-free welding is likely to cause cold welding. Second, select test points. According to the complexity of the PCB assembly board and number of channels in the collector ( General collector has 3 ~ 12 test channels) , the choice of at least three or more can reflect high on a board assembly (PCB surface The most hot) , medium and low ( The most cold spots) The temperature of the representative test points. The highest temperature ( Hot) Generally in the middle of the chamber of a stove or furnace, few components or components and small components; The lowest temperature ( Cold spots) General in the large components ( Such as PLCC) , copper in large cloth, transmission guide or furnace hall edge location, blowing hot air convection. Third, fixed thermocouples. With the high temperature solder ( Sn- 90 pb, melting point solder of more than 289 ℃), The test end of dogan thermocouple respectively welding in the test point ( Solder joints) , before welding of solder in the solder joints must be clean; Or the test end of thermocouple respectively with high temperature adhesive tape paper sticking to the PCB various temperature test point location, no matter adopt what kind of way fixed thermocouples are required to ensure weld, cements, clip. The other end of the four, the thermocouple insertion machine mesa of 1, 2, respectively. . Jack position, or inserted into the collector outlet, pay attention not to reverse polarity. Thermocouple number and remember each thermocouple on the surface mount board relative position, shall be recorded. 5, will be measured on the surface of PCB assembly board placed at the entrance of reflow welding machine transmission chain/net belt ( If you use the collector, the collector should be placed behind the surface of the PCB assembly board, just to keep some distance, about 200 mm) above The test program, and start the KIC temperature curve. Six, with the operation of the PCB, drawing on the screen, Display) The real time curve ( Equipment with KIC test software) 。 After seven when PCB cooling zone, pulls the thermocouple line will drift back PCB assembly board to complete a test process at this time, displayed on the screen full of temperature curve and peak temperature/timetable ( If the collector temperature curve is used, the PCB from the reflow soldering furnace exit and collector, and then through the software read temperature curve and peak temperature schedule) 。 Eight, input corresponding client code or name of the file, save. Or according to customer's actual needs of real-time temperature curve can be printed. In case the customer checking and surface archive.
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