SMD LED is a new surface mount semiconductor light-emitting device , with a small scattering angle is large , light uniformity, high reliability , light colors including white colors , it is widely used in a variety of electronic products . PCB board is one of the major manufacturing SMD LED material . Development of each new product are SMD LED PCB board design drawings from the beginning, in the design of the front and back graphics should be given PCB and SMD LED assembly drawings and the finished map , then good PCB board design drawings to a professional LED PCB board manufacturers producing tablets plates, designed to implement a direct impact on product quality and manufacturing processes. Therefore, the design of a flawless SMD LED PCB board is not an easy thing, must take into account many factors influence the design. Therefore, this article from the following aspects of SMD LED PCB board design are discussed.
First, SMD LED PCB board structure selection
SMD LED PCB board types according to the structure: There conduction hole structure, pocket hole structure ; based on single SMD LED chips used in quantities of : monocrystalline , double and three crystalline polymorphs . On- hole PCB board structure and the structure of the PCB hole pocketing the difference is : the need to cut in both directions when the former cut , single semi- finished electrode arc ; just cut in one direction when the latter cut. Choose what kind of structure design and SMD LED PCB board using a few chips approach is based on the market requirements of the user . When the user does not make special requests , usually selected pocket hole PCB board design . PCB substrate is BT board.
Second, the choice of the direction of the pocket hole
If you choose to use pocket hole structure design the PCB board, pocket hole must be considered to choose which direction . Normally the holes are designed pocket along the width direction of the PCB board , because it can make the PCB deformation produced by compression molding a minimum .
Three , PCB board Dimensions choose
Each factor to choose a new SMD LED PCB board size dimensions must be considered : ① Quantity each PCB board design products . PCB deformation extent ② compression molding is within the acceptable range.
When not affect the production process, the number of each product as the PCB design multi-point , this will help reduce the cost of a single product . Also, because the gel will shrink after molding , PCB board easily deformed , so the PCB will have to consider in the design of each set of SMD LED quantity can not be too much, but a few groups can design points. This will satisfy a single PCB board SMD LED quantity requirements , and does not cause the gel contraction caused by compression molding deformation of PCB board is too large . PCB board PCB board will result in a larger deformation can not be cut , and the cut of Colloid and PCB board easy to peel .
PCB thickness option is to be determined based on the overall thickness of SMD LED requires users. PCB thickness is not too thick , not too thick wire will cause the solid crystal ; PCB board thickness can not be too thin, too thin can cause shrinkage after compression molding because colloids , PCB board deformation is too large.
In 0603 the general specifications thickness of 0.6mm SMD LED products as an example . If you choose the thickness of 0.3mm PCB board, the thickness of gel may only 0.3mm, 0.28mm thickness and then choose a solid crystal wafer , the overall thickness is already 0.58mm, wire bonding operation can not be performed . If you choose to 0.1mmPCB plate thickness , the thickness of gel is 0.5mm, the compression molding due to the colloidal thick , clear gel contraction , while thin PCB board , PCB board deformation this would generate too large. Therefore, when the thickness of the PCB design must choose an appropriate thickness , both make the same piece of PCB board suitable for different thickness of the chip SMD LED, and will not cause deformation after compression molding PCB board is too large .
Four , PCB circuit board design requirements
1, the solid crystal District : design solid crystal size is determined by the area of the chip size. In good solid chip to meet the energy security situation , solid crystal area to design some as small as possible . Such colloidal die after the PCB will be better adhesion , easy to produce the PCB stripped colloidal phenomena , but also consider the design of solid crystal region as single SMD LED circuit board in the middle position.
2 , wire District : District basically wire is greater than the size of the magnetic nozzle at the bottom .
3, the solid crystal area with wire distance: solid crystal region and the region from wire to wire to wire to determine the arc , arc line tension resulting from the General Assembly is not enough, from small will cause gold wire in contact to the wafer .
4 , the electrode width: the width of the electrode is generally 0.2mm.
5 , the circuit diameter: diameter electrodes connected to a circuit with solid crystal region should consider the issue size. The use of small diameter to increase the adhesion of the substrate with the colloid .
6 , vias Aperture: If vias PCB board design , vias minimum aperture is generally Φ0.2mm.
7 , punching hole diameter : If the width of the minimum hole vias PCB board design , the pocket is generally 1.0mm.
8, the cut line width: the cutting blade has a cutting because the presence of a certain thickness , PCB board after cutting portion is worn , the cut line width in the design to take into account the thickness of the cutting blade , to compensate for the design of the PCB board , otherwise, the width of the finished product after it is narrow cut .
Also, consider positioning holes pore size and other issues. Usually a PCB board circuit can be designed within the range of the number of products designed to double the number .
Fifth, the quality requirements of the PCB substrate
PCB board design, PCB board production to deal with the following technical description :
1, requires a sufficient precision: the thickness unevenness of claim <± 0.03mm, the positioning hole of the bias circuit on the circuit board <± 0.05mm.
2 , the thickness and quality of the gold layer must ensure that the gold wire bonding after tensile testing > 8g.
3, PCB board after the finished products , requiring no surface dirt , colloidal adhesion between the die and the good .
