PCBA Tech - SMT replacement chip components and point calculation

Tips for replacing chip components in SMT chip processing

In the SMT chip processing industry, electronic components are one of the most contacted materials, and the replacement of chip components is often encountered during processing. This job seems simple, but it is really difficult to operate. It needs to be replaced in strict accordance with relevant requirements.

First, before replacing chip components, prepare a temperature-controllable electric soldering iron with a ground wire, and the width of the soldering iron tip must be the same as the metal end surface of the chip components, and the temperature must reach 320 degrees Celsius. In addition, preparing tweezers, removing tin, fine low-temperature rosin welding wire, etc. are also indispensable.

When replacing, put the soldering iron tip directly on the upper surface of the damaged component. When the solder on both sides of the component and the adhesive underneath have melted, remove the component with tweezers. Immediately afterwards, the residual tin on the circuit board is sucked up with a tin removal strip, and then the adhesive and other stains on the original pad are wiped with alcohol.

When PCBA is processed, usually only a proper amount of solder is applied to one pad on the circuit board; then use tweezers to place the component on the pad. In order to quickly heat the tin on the pad, the molten tin contact chip component needs to be placed on the metal end, But never touch the component with a soldering iron tip.

It should be noted that as long as one end of the newly replaced chip component has been fixed, the other end can be soldered, but pay more attention to heating the pad on the circuit board and add an appropriate amount of solder to make the pad and the component end face Form a bright arc. The amount of solder must not be too much, so as not to flow under the component and short-circuit the pad; for the same reason, only the molten tin can be dipped into the metal end of the component during soldering, and the soldering iron tip should not touch the component to complete the entire replacement. process.

SMT patch processing point calculation method

SMT patch processing points calculation method:

In product dispatch factories and processing plants, engineers often have to calculate product processing fees. How to calculate SMT processing fees?

1. Understand the smt production process and the content of each process:

Feeding--Printing solder paste--SMD components--Visual inspection--Reflow oven--Ultrasonic cleaning--Cutting--Appearance inspection--Packaging (some products require IC programming and PCBA function testing)

2. Calculate the number of patch components:

SMT chip processing fee is generally calculated based on the number of component points. For smt chip processing, one chip (resistance, capacitance, diode) is counted as one point, one transistor is counted as 1.5 points, and the four pins of IC are counted as one point, and the PCB board is counted. All placement points on the board.

3. Calculate the cost

Processing fee = point * unit price of 1 point (processing fee includes: red glue, solder paste, washing water and other auxiliary materials)

4. Other expenses

The cost of measurement frame, steel mesh and other agreed upon by both parties shall be calculated separately.