Monday, October 28, 2013

The Basic Parts of a PCB Circuit Board

PCB, short for Printed Circuit Board, is playing increasing important role during our daily life. It makes the circuit miniaturize and visualize, and its essential role of fixing batch production and optimizing the layout of electrical equipment can never be ignored.

The circuit boards is generally composed of the following parts:

Pattern mainly refers to the line on the surface. The line is the connective tool between the components. And another copper surface will be designed as the ground and power layer.

It is used to keep the insulativity of the layers and commonly known as the base material.

Through hole/via
The hole can make two or more layers to conduct to each other. Usually, the larger holes are used as parts plug-in, while the NPTH is used to do surface-mount positioning, helping to fix screws when doing assembly.

Solder Mask
Not all the copper surface needs to solder on the parts. So for the area which soldering is not necessary, we will print a kind of material, usually known as epoxy resin, to prevent the copper surface from short circuit between the lines. According to different process, the solder mask can be divided into green oil, red oil and blue oil.

Legend/Silk Screen
This is not a necessary composition. The main function of it is to mark the name and location of the components, and to convenience the repair work after assembly.

Surface Finish/Treatment
Due to the copper surface is easy to oxidize during the general environment, causing poor solder ability. So there is usually a protection layer on the copper surface. And the methods of protection include Hot Air Solder Leveling (HASL), Immersion Gold (ENIG), Immersion Silver, Immersion Tin and OSP.

Circuit board is one of the most active industries in modern electronic components industry. The growth rate of the industry is generally higher than the electronic components industry by 3%. For the wide range of the application of printed circuit board, there must be wider market for it.

Wednesday, October 23, 2013

SMT Stencils of Printed Circuit Board

SMT stencil is an important tool during the PCB assembly. If you are producing a printed circuit board with SMD/SMT components, using a stencil can allow you to apply an even and accurately placed coat of solder paste to the pads. This is often quicker and easier than doing it manually, especially if you working with more than one copy of the same board. A consistent and accurate coat of paste will reduce the number of solder bridges and decrease board cleanup time.

The sole purpose of an SMT stencil is to transfer solder paste to a bare circuit board. A stainless steel foil is laser cut creating an opening for every surface mount device on the board. Once the stencil is properly aligned on top of the board, solder paste is applied over the openings. When the stainless steel foil is separated from the board, solder paste will remain, ready for placement of the SMD. This process, as opposed to hand soldering methods, ensures consistency and saves time.

Stainless steel foil thickness and aperture opening size control the volume of paste deposited on the board. Too much solder paste causes solder balling, bridging, and tomb-stoning. A lack of solder paste creates insufficient solder joints. All of which compromise the electrical functionality of the board.

At Wonderful PCB Limited, we use Laser Technology to manufacture SMT Solder paste stencil, high tolerance aperture openings with superior registration for its solder paste stencils. With its 4 mil beam diameter, our Laser is capable of cutting small aperture openings to meet your size requirements. When you need to make the stencil, please kindly send us the file for production and advise us the size and thickness of the stencil, with or without frame. Normally it takes 24-48 hours to make the stencil. Here is the stencil we produced for you reference.

For more detailed information, please contact Mr. Stephen Zeng at email: . Thanks a lot!