5 steps to teach you to complete the little bear pie development board patch

Time:2021-1-8

Abstract:This article takes you to understand the whole process of the little bear development board patch.

The first step is preparation

The first is the preparation before the formal placement, includingLoadingPreparation of steel meshAnd so on.

1. LoadingThat is, after the factory receives the customer’s bill of materials, the material number and item name are listed in the corresponding machine. At this time, according to the plan, the warehouse will equip the project materials to be produced in advance, and then the production material personnel will put the materials into the corresponding machine according to the material number set in the machine. After the production material personnel load the material, the inspectors cooperate to check whether there is any inconsistency in the material number, and sign on the material loading record. At the same time, there will be special quality inspection personnel to spot check the material loading during line patrol.

5 steps to teach you to complete the little bear pie development board patch

2. Steel mesh preparationThe steel mesh is specially customized by the manufacturer according to the development board of little bear group. The holes in the steel mesh correspond to the pads of components on the PCB board. The solder paste is printed on the pads, and the components are pasted on by the mounter, and then thermosetting is carried out by the reflow welder.

5 steps to teach you to complete the little bear pie development board patch

Second, solder paste printing

The solder paste automatic printing machine will start printing after the steel mesh is fixed and the solder paste is ready. The holes in the steel mesh correspond to the pad of the board, and the solder paste will be printed on the board through the machine. In this step, it should be noted that the solder paste is printed on the board through the holes of the steel mesh, and the accuracy of positioning is directly related to the printing quality of the board, so the holes of the steel mesh and the pad of the board must be aligned.

5 steps to teach you to complete the little bear pie development board patch

Step 3: Patch

Before the placement, in addition to the complex settings of the specific placement on the placement machine, we also need to feed the placement machine (Feida), and start the placement after everything is ready. The patch time of a bear pie development board is about 20s.

5 steps to teach you to complete the little bear pie development board patch

The fourth step is reflow soldering

After the placement is completed, reflow soldering should be carried out in the reflow welder. In the process of hot air reflow soldering, the solder paste needs to go through the following stages: solvent volatilization; the flux removes the oxide on the surface of the weldment; the solution and reflow of the solder paste are used to cool and solidify the solder paste.1. Preheating stageThe PCB and components are preheated to achieve balance, and the moisture and solvent volatilization in the solder paste are removed. It is mild, and the thermal impact on the components is as small as possible. If the temperature rises too fast, it will cause damage to the components, such as cracking of multilayer ceramic capacitors. At the same time, it can also cause solder spatter, forming solder balls and solder joints with insufficient solder in the non soldering area of the whole PCB.2. Soaking stageTo ensure that the solder can be completely dry before reaching the reflow temperature, and at the same time, it also plays the role of flux activation to remove metal oxides in components, pads and solder powder. The time is about 60 ~ 120 seconds, which varies according to the properties of solder.3. Reflux stageThe solder in the solder paste makes the gold powder begin to melt and flow again, replacing the liquid flux to wet the pad and components. This wetting effect leads to further expansion of the solder, and the wetting time for most solder is 60 ~ 90 seconds. The temperature of reflow soldering should be higher than the melting point temperature of solder paste. Generally, the reflow soldering quality can be guaranteed only when the melting point temperature exceeds 20 ℃. Sometimes it can be divided into two stages, namely melting stage and reflow stage.4. Cooling stageThe solder solidifies with the decrease of temperature, which makes the components form good electrical contact with the solder paste. The difference between the cooling rate and the preheating rate should not be too large.

5 steps to teach you to complete the little bear pie development board patch

The fifth step is testing

The common defects in welding production were detected by AOI optical detection instrument. The machine automatically scans the PCB through the camera, collects the image, compares the tested solder joints with the qualified parameters in the database, checks out the defects on the PCB through image processing, and marks the defects through the display or automatic signs for the maintenance personnel to repair. AOI optical detection instrument is used as a tool to reduce defects, and to find and eliminate errors in the early stage of assembly process, so as to achieve good process control.

5 steps to teach you to complete the little bear pie development board patch

I believe that after watching the specific production process of the development board, my friends have a deeper understanding of bear pie.

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