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bga rework station works
bga rework station works
Application of several techniques in ball array package surface mount technology , the widespread use of plastic ball grid array , ceramic and ceramic ball grid array columnar array. Due to the different physical properties of these packages , increasing the difficulty of bga rework of . When repair, using the latest automated equipment, and understand the structure of several types of packaging components and heat removal and re-posted on the direct impact is necessary, so that not only saves time and money , but also saves components, improve the quality of board and achieve a rapid repair service . In many cases , you can fix it yourself bga package, without the need to ask service personnel on-site service professionals . bga rework land package also includes the removal from the defective board other " good " bga components.
All bga rework must follow a basic principle. bga package and must reduce the number of thermal cycles pad exposed to, with the increase in the number of thermal cycles , thermal damage to the pad , the likelihood of solder mask and bga package itself is growing. Situation bga art technology because the ball grid array has a high i / o number , so this technique is very attractive. Due to the expensive cost of x-ray inspection equipment bga often accused of making the necessary testing, and this technique has the advantage of exactly without inspection , mount technology has been achieved with mechanical equipment to direction from a separate device , and can easily draw the printing and reflow profile . However, after the removal of components, additional components to re- solder ball, often can not meet the needs of users .
bga and many other components technologies, if it does not destroy the interconnect material , will not be able bga pcb assemblies removed . In the repair process, because half of the bga solder ball remains in the assembled board , while the other half of the solder balls carried by the elements , and pulled into a filament . For this reason, before the rework required to repair the entire sphere and precast pcb pad. Bga repair method using a method using a pre-formed , according to the requirements of this approach is an array / matrix of the solder ball pitch embedded in an aqueous -based flux . A preformed solder balls generally takes about 1000 , this method is too costly . Preformed under the bga is facing , and then re- flow soldering achieve. Expect the entire solder balls can roll to be able to flush out water soluble based flux , then you can repair on the package . Another method is a replica of the original manufacturing technology , i.e. ; printing bt flux or solder paste on the glass substrate and the solder ball will be automatically filled in the preformed template bga added thickness on the lower face . Excessive solder balls , the template should be removed , the component to be reflow furnace , so as to meet the requirements of the interconnection found . However , application of this method , the cost of a method preformed lower than , the cost of 40/100k sphere, while another method using solder paste can achieve the advantages of lower cost , in addition, the method of applying solder paste , not sphere fibrillation occurs , scattered everywhere phenomenon. When using solder balls to re- package the additional tool , can be combined with the paste solder paste printing method on the component , in the reflow process, so that the template can be retained in position on the element forming the solder balls . When removal of the template , the element has been completely repaired. Re- use of additional solder ball technology curve corresponding set of hot air rework tools , bga components can be removed . Pcb pad must be cleaned once removed excess solder , it should mount components before re- printing solder. Available soldering flux or solder paste will pbga to the welding area. Hand tools available administered liquefied flux and solder paste can be printed viscous manner or spray applied to the mode pad . After mount components , where appropriate thermal curve, re- pcb
The new re-flow . In the reflow process, solder balls on each bt substrate , the ball was flat partial projected height of about 24mil. Pbga pcb mounted on the process flow to be performed and a second time to further " collapse " of each of the solder balls , and finally the height of the projection to about 19mil . solder mask pcb mount area and pore diameter can determine the height after reflow . Typically, this tolerance is sufficient for the cleaning process pbga . It is necessary to remove excess solder bga on when to remove excess solder , solder removal tool can be used , solder braid or use a soldering iron , will repair tool tilted to a certain angle, the contact area of rework required to complete the removal process . bga solder residue on the pad , a small crescent-shaped form , it is clear enough to meet the required amount of solder balls . When removing excess solder , to every element of the heating coil in the form of heat transferred to the component surface to achieve uniform heating . Then, the load is mounted bga appropriate size for the element in the template substrate . Leveling the element in the template , the printing paste used doctor blade into the hole template, with a scraper to remove excess solder paste. Using a hot air tool mount components , and with a suitable temperature profile of the nozzle , the hot air heating effect, so that the element shaking until the solder paste reflow , the solder balls to form a single . Reheating of the center member , or radially outward spiral running operation, the purpose of uniform heating can be achieved .
pbga Currently , pbga is the most common use in bga package. Mainly due to the use of bt resin substrate pbga 2-4 layers. Silicon chips are glued with epoxy adhesive to a specific location on a substrate above , and then wire bonded to its turnover , etched copper on the road. The copper wire around the top of the package distribution and the through hole through the substrate opposite the external coupling line . Then, spread to the back line to the bottom of the fan base pad array , similar eutectic solder reflow connected by welding area for the pcb pad provides pbga interface. Next, the liquid photoimageable solder mask is applied to the top of the periphery of the substrate , the epoxy resin molding compound is applied over at assembly , and cured. This is assembled to create the conditions and provide the rework operation protection. 0.030 pbga diameter solder balls , similar to the eutectic composition is generally ball 62sn/36pb/2ag , the spacing of the solder 50-60mil. solder ball bonding pads pbga bottom of the solder mask substrate optical imaging. In pbga manufacturing process , the base substrate coated with flux , solder is applied to the ball , and then the flow . Only pbga manufacturing process , the base substrate coated with flux , solder is applied to the ball , and then the flow . Only the amount of solder pbga solder balls is sufficient for each solder joint applications. cbga ceramics and plastics in many respects bga bga package there is a clear difference. cbga using 0.035 diameter : height of the solder ball of non- collapsed , and not the diameter of 0.030 eutectic alloy solder ball. In the manufacturing process , the eutectic solder alloy of these large solder balls connected to the bottom of cbga . Methods to spray their way north or template eutectic solder paste printing DPRK to adhere to the board. In the reflow process, solder balls due cbga will not collapse , the package body to delve into the plane change pads between the circuit board and more sensitive . cbga bottom preheating process requirements more precisely to reduce warpage and plane change board. Cbga dismantling process, the same as the removal pbga some high temperature solder balls adhered to the solder remains on standby and the other has been removed in the solder ball pad cbga liquidation . In the cleaned pads ready cbga Process, the flow must not be at a high temperature to avoid deposition of material on the pad lesions , as long as the temperature reaches the eutectic alloy solder reflow to the purpose of welding to stick to the accompanying need to be able to achieve a reliable board sex . The removal of solder balls may tweezers or other tools. High temperature solder and solder on the pad compounds , will give future pads superalloy repair extremely difficult forest . After cleaning up the pad and re -mount bga, and tack welding . As described above , the available printing paste or flux method , adhesion pbga. Because the sensor resistance and high-temperature solder balls collapse of non- planar , only use paste adhesive cbga. For these two packages can also be used with the method of spraying a small solder paste stencil printing method of administration . Occasionally , because the template is not aligned , spherical solder ball is not flat , that is aligned with the center of the pad . To correct this phenomenon , it should be removal of the template , and in heated conditions, coated with solder re- flow components . Solder will " spherical " , and by the surface tension of the solder centering .
However , this is called " rework renovation " technique is rarely used. Such additional to re- solder balls bga technology is to work, because:
1 , most of the flux is not wet except template , lemon -based flux . Once the solder is adhered to the hole template , it will reduce the quality of the board. Use the recommended flux composition is hundreds of times to use a template, all need to replace , or even to be used thousands of times .
2 , due to the paste into a solid sphere , making the paste volume is reduced, it will make the hole larger than the radius of the sphere radius , so you can easily take down a template from the component will especially after cleaning .
3 , the template is made of cold rolled stainless steel alloy , resulting in individual particles of the metal stretching . Regardless of which surface is heated , metal bent in one direction only . The plate was positioned so, when heated , the heating element which faces towards the board will bend. This led to the board memory metal component is pushed up against the establishment in bga solder seal around each pad . This " dam " of the solder will not flow to the other pad , whereby the uniform size of the solder balls . After cleaning the bga , can be aligned and mounted onto the pcb, and then re-flow , bringing the component repair is completed, it should be noted that the use of manually cleaning pad is not completely remove impurities. If the repair can not use electricity for cleaning, repair before , you should consider using a no-clean solder paste or flux . Conclusion bga rework and repair operator has a close relationship with the successful rework bga requires the operator to have the structure of the package with the removal and re-posted areas , proper operation of the thermal characteristics and create curves knowledge , equipment, and strictly in accordance with the development of technology operation, in order to ensure uniform consistency and success bga rework . Bga rework elements can help you save time and money. Such savings can make demands customer satisfaction and management. Both types can be considered an element of the above-described process for the repair of any rework / repair operations in order to effectively use expensive components.