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              Technology Exchange

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              PCB storage requirements

              1、before use should be stored in packaged form at a temperature not higher than 35 ℃, relative humidity less than 75%, non-corrosive gases indoor environment; 

              2、the surface coated with anti-oxidants or bare copper PCB fluxes and save 3 months; 

              3、the surface was covered with tin-lead or nickel-plated metal layer PCB, gold, etc., shelf life of six months; 

              4、PCB assembly and welding process within 48H before unpacking Tips: If it exceeds the effective shelf life, according to relevant regulations before the warranty for the performance of certain performance tests again, after passing inspection may be appropriate to deal with, qualified products can still be used.

              PCB characteristics of different surface treatments

              1、Surface treatment: gold(ElectrolyticNi/Au) 

                Gold plate process relative to other types of higher costs, but now all of the existing plate the most stable and most suitable for use in green manufacturing process, especially in some high-priced or require high reliability electronic products are recommended. 

              2、Surface treatment: OSP board(OrganicSolderabilityPreservatives) 

                OSP process lowest cost, easy to operate, but this process due to be fitted with factory modified equipment and process conditions and Heavy poor and therefore popularity still poor, the use of this class of plates, after high-temperature heating, pre-coating on PAD The protective film is bound to be destroyed, resulting in reduced solder, especially when the substrate after the second reflow the situation is more serious, so still need to go through the process again if DIP process, then the end will challenge DIP welding on. 

              3、Finish: silver plate(ImmersionAg) 

                Although the %"Silver%" itself has a strong migration, resulting in the case of the occurrence of leakage, but today's %"immersion silver plating%" is not a simple metallic silver in the past, but with a total organics plated %"organic silver%" thus has been able to meet the future on demand lead-free process, which can be life weldability is also longer than the OSP board. 

              4、Surface treatment: of gold plate(ElectrolessNi/Au,ENIG) 

                The biggest problem is the point of such a board, %"black mat%" (BlackPad) problem, so the lead-free process there are many manufacturers do not agree to use, but most of the domestic manufacturers to use this process.

              5、Surface treatment: tin plate(ImmersionTin) 

                Such substrates easily contaminated, scratches, plus process (FLUX) oxidation discoloration will occur, most domestic manufacturers do not use this process, the cost is relatively high. 

              6、Surface treatment: HASL (HASL)

                Because low-cost, good solderability, good reliability, compatibility of the strongest, but this excellent welding characteristics due to the presence of lead HASL, so you can not use lead-free process.

              PCB FAQs

              A、Overlapping pads

              1、Pad (except the outer surface mount pads) overlap, means overlapping holes, in the drilling step because drilling at times lead to a broken drill bit, resulting in damage to the hole. 
              2、Multilayer two holes overlap, such as a hole for the isolation plate, the other holes for connecting plate (flower pads), so that after the film depicts the performance of the isolation plate, resulting in scrap.

              B、Abuse graphics layer

              1, in some graphics layer made some useless connections, originally designed four-layer board has more than five lines, so misleading.

              2, the design of the easy way to Protel software as an example of the layers have to draw the line with the Board level, but also with the Board level to draw dimension line, so when making gerber data because unselected Board level, missing connection and disconnection, or because of the choice of dimension lines shorted Board layer, thus keeping intact the graphics layer and a clear design. 

              3, in violation of conventional design, such as components in Bottom layer face design, welding surface design at Top, causing inconvenience.

              Misplacing C, characters

              A character cover pad SMD solder tabs to weld-off test and components PCB inconvenience. 2, the character design is too small, causing difficulties in silk screen printing, and too much will make the characters overlap, it is difficult to distinguish.

              D, single pad aperture settings

              1, single-sided pads generally not drilling, drilling should be labeled if its aperture should be designed to be zero. If the design value, so that when generating drill data, and the position coordinates of the hole appeared, and problems. 2, one-sided as drilling pads should be marked as such. 

              E, short pad surface mount devices

              This is an on-off test in terms of, for too dense surface mount devices, the spacing of their feet between the relatively small, the pad is quite thin, installation and testing of the needle must be down (left) staggered position, such as pads design is too short, while not affecting the device is installed, but will test pins wrong not open position.

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