Surface Assembly Basic Process Flow

Alright folks, let's talk about Printed-Circuit Board Assembly or PCBA, just rolls off the tongue doesn't it?! Well, it's basically the process of soldering components onto the board. Now, there are two ways we do this: reflow soldering and wave soldering. If you wanna get technical, they're like Batman and Robin. They each have their own unique abilities but together they make the perfect crime-fighting duo - in this case, assembling our SMT! So sit back, grab some popcorn, and watch these soldering methods come to life!

Reflow Soldering

Reflow soldering, refers to the melting of pre-printed in the PCB pads on the solder paste, surface assembly components to achieve the solder end or pin and PCB pads connected to a soft brazing soldering process.

1.  Process Characteristics

(1) The application of solder (in the form of solder paste) and heating are carried out separately, and the size of the solder joint can be controlled.

(2) Solder paste is distributed by means of printing, and only one stencil is generally used for solder paste printing on each soldering surface.

(3) The main function of the reflow soldering furnace is to heat the solder paste, i.e., the PCBA placed in the furnace is heated as a whole, and the solder joints welded for the first time will be re-melted when the second soldering is performed.

2.  Process:  Flow printing solder paste → patch → reflow soldering.

Wave Soldering Process

Wave soldering refers to the melting of the soft brazing solder (solder containing tin), through the mechanical pump or electromagnetic pump jet into the solder wave, so that the pre-equipped components of the PCB through the solder wave, components to achieve the solder end or pin and PCB jack / pad connection between a soft brazing soldering process.

1.  Process Characteristics

(1) Apply solder and heat to the PCB.

(2) The application of heat is mainly conducted through the melted solder, the size of the heat applied to the PCB mainly depends on the temperature of the molten solder and the contact time between the molten solder and the PCB (soldering time).

(3) The size of the solder joints, filler mainly depends on the design of the pads and the mounting gap between the holes and the leads. In other words, the size of the wave soldering joint depends mainly on the design.

(4) Soldering SMD, there is a "mask effect", easy to leakage phenomenon. The so-called "masking effect", refers to the chip SMD package body to prevent the solder wave contact to the pad / solder end of the phenomenon. (2) process flow dispensing → patch → curing → wave soldering.