Many electronics companies focus on design, R & D and marketing, and outsource electronics manufacturing. From product prototype design to market, there are many development and testing cycles, of which sample testing is critical. When delivering the designed PCB files and BOM list to the electronics manufacturer, it is also necessary to analyze from multiple perspectives to ensure that there are no delays in the project cycle and reduce the risk of product launch.

First, if it is a high-end electronic product, the material must be strictly selected at the sample stage, the packaging process must be ensured, and the real batch production process is simulated as much as 100%. If it is a very common electronic product and the solution is very mature, then concession reception can be performed at the sample stage, such as using some alternative materials, expanding the scope of ICT test acceptance, and so on.

Second, PCBA sample production must follow the principle of speed over cost. It usually takes 5-15 days to send the PCBA samples back to the hands from the design plan. If the control is not good, this time may be extended to 1 month. If there is a time delay caused by human factors, it will have a great negative impact on the project schedule. In order to ensure that we can receive PCBA samples within the fastest 5 days, we need to start to choose electronic manufacturing suppliers during the design stage (with process capability, good coordination, focus on quality and service), and even pay 50% more prototyping cost.

Third, the design plan of the electronic product design company must follow the specifications as much as possible, such as the reservation of heat dissipation holes for circuit board design, the labeling of silk screens, the normalization of materials in the BOM list, the clear labeling, and the clear remarks on process requirements in the Gerber file. This can greatly reduce the communication time with the electronics manufacturer, and also prevent erroneous production caused by unclear labeling of the design scheme.

Fourth, fully consider the risks in logistics and distribution. In PCBA packaging, electronics manufacturers are required to provide safe packaging, such as bubble bags, pearl cotton, etc., to prevent collisions and damage in logistics.

Fifth, when determining the number of PCBA samples, the maximum principle is used. Generally, project managers, product managers, general managers, and even market personnel may need prototypes. In addition, it is necessary to fully consider the burn-in that occurs in the test. Therefore, it is generally recommended to proof more than 10 pieces.

1. Why is the engineering fee charged for PCBA prototyping?

Engineering costs refer to the production of information files, the production of stencils, the commissioning of equipment, and the replacement of SMT lines. Because the order is too small and the minimum consumption level has not been reached, these engineering costs need to be charged. The engineering fee for PCBA prototyping is mainly charged in the PCB production and SMT / DIP.

1.1. PCB Engineering Fee
Although the number of PCBs is small, when producing PCBs, it is necessary to produce according to the production process, and special equipment and manpower are required to produce, which will cause a relatively high average production cost. If the calculation is based on the unit price of mass production, PCB manufacturers will inevitably lose money. Therefore, PCB manufacturers generally charge engineering fees accordingly to maintain normal production.

1.2. SMT / DIP Engineering Fee
Before the SMT chip processing, the data needs to be sorted, the SMT stencil is opened, the first item must be confirmed, and the machine must be debugged. During this period, a lot of labor and time costs will be involved. These are electronics products Developers to bear. Therefore, general electronics processing plants will charge engineering fees according to the minimum consumption standards.

2. What does the PCBA processing plant mean by the setup fee?

The PCBA processing plant's machine-up cost refers to the machine-up consumption cost of the SMT chip processing. SMT chip processing requires fast and efficient production. General SMT chip workshops will carry out non-stop production, machine shutdown and line change are increasing production costs and reducing profits. Therefore, for some small batch orders will often be charged on set-up fee.

3. What kind of documents do I need to provide when I take the PCB board to the PCBA factory for assembly?
You need to send the necessary information files to the assembly factory first. After the assembly factory has seen it, it can be produced without any problems.

The files that need to be provided to the PCBA patch factory are: PCB files, BOM list, Pick and place, and samples.
3.1. PCB files are used to make stencils and can also be used to locate patch coordinate files, which can guide production.
3.2. The BOM is also the bill of materials. It is used to check whether the material is wrong and an indispensable document.
3.3. Pick and place. It is not necessary, but for positioning the coordinates of the assemply machine.
3.4. The sample can be used for the furnace temperature test, and it does not necessarily need to be provided.
Entrust PCBA assemply factory for processing, it is best to provide complete information to facilitate the production of the assemply factory.

4. How long is the PCBA assemply processing?

During PCBA assemply processing, when the customer's material arrives, the material needs to be counted, and SMT stencil, equipment debugging, first item confirmation, etc. need to be made. These all take time. It is mainly related to the size of the batch. The small batch order can be completed within 7 days. The production cycle of the large-scale assemply order is as follows:

Batch 1000-5000, Lead time 15 days
Batch 5000-20000, Lead time 17 days
Batch over 20,000, Lead time 20 days

5. How to control PCBA assemply quality efficiently?

The PCBA assemply process mainly includes solder paste printing, assemply, reflow soldering and AOI inspection. The process is relatively complicated. Irregular operations in any link will seriously affect the PCBA quality. Among them, the quality of PCBA can be controlled through the key links of Stencil Making, Solder Paste Control, Reflow oven temperature curve setting and AOI inspection, so as to effectively improve the quality of soldering.

5.1. Stencil Making
The solder paste is leaked to the corresponding pads of the PCB through the stencil. The quality of the stencil has a very important effect on the soldering effect of the PCB pads. There are many defects such as more tin and less tin, and the openings of the stencil are very big relationship.
Attention should be paid to the following matters during the acceptance of the stencil:
1. Check whether the method and size of the steel mesh opening meet the requirements
2. Check whether the thickness of the steel mesh meets the product requirements
3. Check if the frame size of the steel mesh is correct
4. Check whether the steel mesh is completely marked
5. Check if the flatness of the steel mesh is level
6. Check if the stencil tension is OK
7. Check whether the position and quantity of the steel mesh openings are consistent with the GERBER file
A good stencil can miss the printing of good solder paste, laying a good foundation for improving the subsequent welding quality.

5.2. Solder Paste Control
Solder paste is used as a soldering material for PCBA processing. The quality of solder paste has an important impact on the final soldering quality, and it is necessary to strictly control the solder paste.

5.2.1. Solder Paste Preservation
The storage temperature of the solder paste is between 0 and 10 ° C. If it exceeds the storage temperature range, the temperature range of the refrigerator needs to be adjusted.
The life of the solder paste is 6 months (unopened).
Do not place solder paste from the refrigerator in a place exposed to sunlight.

5.2.2. Use of solder paste
1. Before opening, the temperature of the solder paste must be raised to the ambient temperature (25 ± 2 ℃). The temperature recovery time is about 3-4 hours. It is forbidden to use other heaters to increase the temperature instantly. The stirring time using a blender is 1-3 minutes, depending on the model of the blender.
2. Depending on the production speed, the amount of solder paste on the steel net is supplemented in a small amount of multiple additions to maintain the quality of the solder paste.
3. Unused solder paste on that day should not be placed with unused solder paste. It should be stored in another container. Solder paste is recommended to be used up within 24 hours at room temperature after opening.
4. When using it the next day, you should first use the newly opened solder paste, and mix the unused solder paste with the new solder paste at a ratio of 1: 2, and add and use it in small amounts and multiple times.
5. Change the wire for more than 1 hour. Please scrape the solder paste from the steel plate before changing the wire and put it in the solder paste can.
After solder paste is continuously printed for 24 hours, due to air pollution and other pollution, in order to ensure product quality, please follow the method of "Step 4".
6. Please control the indoor temperature to 22-28 ℃, humidity RH30-60% is the best working environment.

5.3. Reflow oven temperature curve setting
The setting of reflow soldering parameters is the key to affecting the quality of soldering. Through the temperature curve, it can provide accurate theoretical basis for the setting of reflow furnace parameters. Each product has a corresponding temperature curve. When reflow soldering of new products, the furnace temperature tester needs to be tested again.

Key places affecting furnace temperature:
1. Temperature setting value in each temperature zone
2. Temperature difference of each heating motor
3. Speed of chain and mesh belt
4. Ingredients of solder paste
5. PCB thickness and component size and density
6. Number of heating zones and length of reflow
7. Effective length of heating zone and its characteristics
Only with good furnace temperature curve can we set the welding parameters in accordance with the product and improve the quality of reflow soldering.

5.4. AOI inspection
AOI inspection is usually placed behind the reflow soldering process. AOI can detect many defects in the previous process, such as more tin, less tin, polarity direction, and monuments. AOI inspection can detect the problematic PCB board, avoiding the problematic board flow in the subsequent process, is a very important link to improve the quality of PCBA.

In the process of PCBA processing, there are many factors affecting product quality. By strictly controlling the above-mentioned several key points, PCBA  quality can be efficiently controlled.