PCBA process flow

1). Loading the board on the board is to flow the empty PCB board into the production line track:

The PCB carrier and the PCB should be fully fixed to prevent the device from being offset due to offset during SMT.

2). Laser marking is to mark a unique serial number on each PCB. Generally, I prefer to use QR code now:

The information contained in the QR code mainly includes production batch, circuit board model, manufacturer information, etc. for the subsequent process to query the produced products and the later SQE traceability of defective products.

3).Print solder paste, and print the solder paste onto the PCB through the opened PCB stencil template:

This is a more critical step. First of all, the steel mesh should be opened well, such as:

Material: stainless steel;

Thickness: 0.08±0.005mm;

Process: SMT laser + electropolishing;

Component accuracy: ±0.1mm;

Resistor parts are generally opened at a ratio of 1:1, and IC chips are cut inside and expanded outside.

Secondly, the activity of the solder paste should be good, and the tin climbing should be excellent.

4). Solder paste inspection, referred to as SPI, is to detect whether the solder paste printed on the PCB is full, uniform, and without offset:

The key point is whether it can detect abnormal conditions such as offset, poor molding, tin deficiency, collapse, tin tip, short circuit, etc.

5). The placement process, referred to as SMT, or the main steps of PCBA, is to mount components to the corresponding device position of the PCB board:

The equipment is generally a Panasonic or Samsung placement machine. Good machines have high precision and few abnormal situations such as missing paste and offset.

6). Visual inspection, that is, the SMT operator checks to see if the SMT patch is in good condition during the first PCBA:

If the device is not pasted well, such as missing, wrong, misaligned, etc., they will constantly check and correct the parameters.

7). Reflow soldering is to pass the PCB with the attached device through a high temperature box, and the solder paste is melted and soldered:

The temperature of the reflow equipment is generally required to be ±1°C. The furnace temperature curve is divided into a preheating zone, a constant temperature zone, a reflow zone, and a cooling zone, which are generally set according to the reference reflow soldering curve given by the solder paste manufacturer.

8). Component inspection, referred to as AOI; to detect whether the device has any deviation, continuous welding, missing QR code printing, etc.:

The key point is that the detection accuracy of the equipment should be high enough, such as ±15um, so that the bad patch can be effectively detected and marked.

9). The plug-in process, referred to as DIP; is to insert the plug-in device into the circuit board, and most devices can be inserted into the machine:

However, a few irregular, non-standard, large, thick and heavy components such as transformers and radiators rely on manual operation and then wave soldering or manual soldering after insertion:

10). Electrical test, referred to as ICT, mainly uses thimble or flying probe to point the test points on the PCB to test the on-off characteristics of the device, and whether the materials used are wrong to ensure the quality:

11). X-ray scanning, referred to as X-ray; mainly for X-ray scanning of BGA, QFN and RF products with shielding covers, to ensure normal soldering and mounting:

12).Function test, referred to as FCT; it is to build a product test tool, simulate the function of the whole machine, enter the quick test mode to test the function of each component, and ensure that the board can run normally:

13). Packing and storage, in fact, moisture-proof oil and three-proof paint are also applied here. The packaging is generally vacuum anti-static packaging, and then labelled and packed into storage: