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SMT Capability

What information is required for SMT processing at PCBA factory?

In SMT processing, when evaluating and quoting, the following information needs to be given to the SMT plant, so that engineers and purchasers can evaluate the process and quotation.

In PCBA SMT processing, if you need the supplier to provide one-stop PCBA processing service, then the communication and cooperation in the early stage need to be more adequate. The contract for labor and material service requires PCB board manufacturing information and assembly instructions, BOM list, Gerber information, etc. The lack of a certain item of information will cause an increase in communication costs and delays in delivery, which will have a very large impact on the timely launch of the product. So today we start from the SMT supplier's angle of view, and analyze why we need relevant information:

1. Gerber data, (includes Pad layer, solder mask layer, silk screen layer, and paste layer)

It is a highly authoritative document in SMT processing, because the follow-up PCB quotation and assembly quotation all need Gerber files for reference. The stencil must be used for SMT processing, so the information of the stencil layer must be known when making stencil.

2. BOM list (component list)

It is what materials are included on a PCBA board. These corresponding materials have different brands, part numbers, and specifications, so the prices are also different, and the calculation of the assembling fee also needs to be evaluated based on the quantity of the components.

3. Coordinate file

It mainly locates the coordinates of the components, and the file is needed when SMT engineers make assembly program for the PCB project.

4. Process instruction document

For controlling the process in PCB assembly factory, it will generally contained as some guidance documents for the PCB manufacturer, including special needs and special design points.

5. Test instructions

There are various test items and categories, including test parameters and technical indicators, and abnormal on-site treatment methods.

The above 5 points are the information needed in SMT processing.

The main features of Surface Mount Technology

SMT process is now more and more mature for electronics manufacturing. What are the main features of SMT PCB Assembly process, today China SMT factory will introduce to you.

1. High density

Since the number of pins processed by SMT is as high as hundreds or even thousands, the center distance of the pins can reach 0.3mm. The high-precision BGA on the circuit board requires fine lines and fine spacing, and the line width is reduced from 0.2~0.3mm to 0.1mm or even 0.05mm, the double wire between the 2.54mm grid has developed to 4, 5 or even 6 wires. Thin lines and fine pitches greatly increase the assembly density of SMT.

2. Small aperture

Most of the metallized holes in SMT are not used to insert component pins, and no welding is performed in the metallized holes. The metallized holes are only used as electrical interconnections between layers, so the aperture should be reduced as much as possible to provide more space for the SMT. The aperture has changed from 0.5mm in the past to 0.2mm, 0.1mm and even 0.05mm.

3. Low thermal expansion coefficient

any material will expand after heating. Polymer materials are generally higher than inorganic materials. When the expansion stress exceeds the material bearing limit, the material will be damaged. Due to the many and short SMT pins, the CTE between the device body and the SMT is inconsistent, and device damage caused by thermal stress occurs from time to time. Therefore, the CTE of the SMT circuit board substrate should be as low as possible to suit the matching with the device.

4. Good high temperature resistance

Today, most circuit boards today need to install components on both sides. Therefore, SMT processed circuit boards need to be able to withstand two reflow soldering temperatures. At present, lead-free soldering is widely used, and the soldering temperature is higher. After soldering, the circuit board is required to have small deformation and no blistering, the pads still have good solderability, and the surface of circuit board still has a high flatness.

SYS Technology is an electronics contract manufacturing factory since 2006, with SMT lines and wave soldering line in house. We have 100+ professionals waiting to service you. Contact us today: sales@syspcb.com.

SMT Component Placement Process Of Parts : Manual Placement

1. Manual mounting process requirement

(1). Improve the production efficiency as much as possible, under the condition of certain human and material resources, achieve the purpose through reasonable arrangement work procedure and adopt the best operation method.

(2). Ensure the excellent and stability of product quality. This is reflected in the production process of the product components, semi-finished products in the production line of the high rate of straight-through, the finished product inspection pass rate is high, good consistency of technical indicators; finished products in the unqualified products in the return of failure causes no instability factors or abnormal failure.

(3). Ensure that each component can work normally in the whole machine with its original performance after installation. The performance of the components should not be reduced or the parameters should not be changed due to improper installation process.

(4). Develop detailed operating specifications. For those installation processes that directly affect the performance of the machine, as far as possible, the use of special tools to reduce the arbitrariness of manual operation.

(5). The arrangement of the work sequence to facilitate the operation, in order to maintain the orderly arrangement and transfer of work between. In the installation process, to install large components, auxiliary parts, combined parts on the frame or base plate, when installing, inside and outside, up and down, left and right should have certain regularity, also pay attention to the shape symbol and mark position of each installed device, easy to observe when checking and also pay attention to the sequence order when combining.

2. The application scope of manual mounting

(1)、Because individual components are loose parts, special components don't have corresponding feeder, or because of the device's pin deformation and so on various reasons cause can't realize on the pick& place machine to mount, as the machine mount after the supplementary mount.

(2)、A small amount of new product development stage or small batch production;

(3)、Because of the financial shortage, has not introduced the mounting machine, at the same time the product assembly density and difficulty is not very big.

First, application of solder paste:

Use simple printing tool manual printing solder paste process or manual dispensing machine drop coating solder paste process.

Second, manual mounting:

1. Manual mounting tools

stainless steel tweezers

suction pen

anti-static workbench

anti-static wrist strap

2. Placement order

1), first place small components, then place big components.

2), first place short component, after place high component.

3), First light and then heavy. The installation process, first installs the light component, after installs the heavy device.

4), first after the example installed. Installation process, while using the example, screwing, welding and other processes, should first example, then screwing, and finally welding.

5), first inside and then outside. In the combination of parts to connect the whole machine, first from the combination of the rack for installation, and then gradually installed to the outside.

6), Generally arrange the assembly line mounting station according to the kind of components. Each person pastes one kind or several kinds of components; The components with more quantity can also arrange several pasting stations.

7), Can set up an inspection station behind each mounting station, also can set up an inspection station after several stations, also can complete the whole version inspection after mounting. To set according to the density of the assembly board.

8), first load conventional, common components, after loading fragile components, can prevent damage in installation.

9), Keep the work site neat and orderly, effectively control the harm caused by the production residue.

10), Installers should be responsible and develop good working habits.

11), The strict operation procedure, the complete protection measure, the perfect fire prevention and the safe use point regulation system etc. are the factors that cannot be ignored in the production.

3. Manual mounting method

1) Momentary type, cylindrical Chip component mounting method. Hold the component with tweezers, align the component solder end with the pad at both ends, put it on the pad solder paste centrally, the polar component mounting direction should conform to the requirement of the drawing, after confirming the accuracy, press it gently with tweezers, make the component solder end invade the solder paste.

2) SOT mounting method Hold the component with tweezers, align the solder end of the component with the pads at both ends, and put it on the pad solder paste centrally, and gently press the component with tweezers after confirming the accuracy, so that the pin of the component is not less than 1/2 thickness into the solder paste, and all the pins of the component are located on the pad.

3) SOP, QFP mounting method Device 1 pin or front mark align with the front mark of the printed character, hold or suck the device with tweezers or suction pen, align with the mark, align with the pads on both sides or four sides, center the device, and gently press the top surface of the device body with tweezers so that the component pins are not less than 1/2 thickness into the solder paste, requiring all the component pins to be located on the pad. Pin pitch 0.65mm below the narrow pitch device should be mounted under 3~20 times microscope.

4) SOJ, PLCC mounting method SOJ, PLCC mounting method is similar to SOP, QFP, because the pins of SOJ, PLCC are at the bottom of the device, so when aligning, it is necessary to check whether the pins and pads are aligned by eye from the side of the device and the PCB board into 45 degree angle.