How to choose rework station BGA


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  1. #1
    Join Date
    May 2012
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    Thumbs up How to choose rework station BGA

    BGA Rework Process Introduction
    1 Introduction
    Defects are caused by many reasons during soldering SMD components as empty soldering, short circuit and others, so repair is necessary. The rework process is simple for common SMD, resistor, capacitor, SOIC, SOJ, PLCC and others. With small alignment are more and more in electronic products, lots of BGA, CSP, QFP and others are more and more, so rework stations become good helpers for operators.
    2 How to Choose Rework Station
    Main differences of rework stations are heat source and heat mode; Take example only upper heat or upper and lower both heating, some can set temperature curve. Considering protecting components, the upper and lower both heating system are better. To prevent PCB warping during repairing, preheat function in the rework system is better. PCB fix, BGA position and others are important consideration.
    3 Rework process
    1) BGA disassemble
    Remove BGA chip with rework system and clean solder residue on PCB with solder iron to make solder pad flat; clean and remove flux residue with special cleaner.
    2) BGA dry
    Please check all BGA chips dry or damp; put damp BGA components into dry box to dry.
    3) Print solder paste
    Print solder paste on disassemble location before soldering BGA; small and special BGA stencil is necessary because there are other components on the board; Thickness and size of stencils are decided by BGA ball diameter and distance.
    For CSP whose ball diameter is <0.4mm, operators can cover flux on PCB solder pad directly.
    4) Mount BGA chips
    Set rework program and put dry BGA into preparation location; rework system will take it automatically and then place it into soldering location.
    5) Solder
    Set soldering temperature according BGA size, PCB thickness and others; then rework station will complete soldering process.
    Take BGA400 rework station from Beijing Glichn as example, more support is from Beijing Glichn S&T Development Co.,Ltd. www.smtchn.com.

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  2. #2

    Default Re: How to choose rework station BGA

    Choosing a BGA rework station Hot Air vs IR


    Hot Air is older and traditional, been around for about a decade. IR is relatively new in the reworking market.

    Hot Air gives uneven heating. IR provides more even heat due to absorption rather than penetration thus a simple benefit of IR is it can remove plastic components, such as a CPU socket, with IR it penetrates the solder joints and does not burn or melt the plastic. IR is usually silent in operation because it has no air flow, while Hot Air uses a forced air system which is heated.

    Technically speaking a Hot Air rework station is more complicated to manufacture than IR in structure and the cost is higher. This is because there are many cables in top hot air heater along with with a fan system. Hot Air uses nozzles which is both a pro and a con, the con is you have to purchase different nozzles for different sizes of chips and the pro is that nozzles can be rotated in 360 degree which very easy for alignment.

    IR stations tend to use ceramic heating plate, they give even heating without causing shift of other surrounding components due to the lack of air movement, but due to the IR plate being a fixed size, you may need to use high temperature tape to cover the surrounding area of the BGA chip. However when using Hot Air you may come across the same issue if your nozzle is not an exact fit or the air flow is too high.

    Many of the expensive machines use Hot Air because well its been around longest and many companies do not want to switch. They have procedures in place and changing them will cost too much. Samsung or Intel with several millions of employees having to retrain and re certify them is too much. Why do you think so many companies still use Win 2K or XP, its all about the transition cost and time.

    IR is newer, but it is gaining much more interest, the reason it has a bad name is due to the inferior plates being used. Higher end plates such as those fitted with Elstein heaters will perform much better. 99% of game console and laptop reworkers have or are using a cheap IR machine probably from ACHI, Scotle, LY, Honton or Jovy. There are very expensive high quality IR machines many of them using focues IR which is an extremely powerful technology.

    Regarding the ACHI brand, it was a brand targeted to be very cheap and that it is, it works but needs lots of experience and upgrades to make it work well. Jovy is targeted to mobile phone reworking and small components thus it works well for that, but many used it for large chips and cause problems thus they hate it and think its inferior. Realizing this, a new version was released which eliminated most if not all of the previous issues. These machines are not in the cheap price range however.

    Any person can perform reworking with just about anything. Anything from an open flame to a million dollar rework station. Heat guns, SMT stations, BGA stations, torches, stoves, ovens and more can all be used as heat sources. Understanding the heat source, using it properly and ensuring that its the right heat source for the job, is where many fail. Many rework technicians attribute their setup as being successful. Having success in regards to any amount for example 60% success rate or even 30% gives the user confidence in themselves and their process.

    Reworking is a science, its not just about heating things. Simplistically it can appear to be that is all we do, heat the chip and remove it. There are many variables involved. MSL moisture sensitivity level, package size and type, environmental variables, pcb thickness and quality, copper planes, flux, solderability and more.

    User A can rework a board and Hot Airve it working in 9 mins with $500 setup. User B can rework in 3 mins with $40,000 setup. Both boards work from both users. Both feel they Hot Airve success, but there are more variables involved. User A board may last a shorter or longer period of time tHot Airn the board repaired by user B. Equipment and user are the biggest factors in reworking. User A may fix 60% of boards and they last 6 mo. User B may fix 90% of boards and they last 2 mo. User B may feel over confident and not user proper profies thus causing both instant and time based problems.

    Variables that affect User B may not be the same for User A thus having less success but longevity. The success rates can also change if the user does not update processes and monitor variables. The same principles can be applied to a chef, chef A is a veteran and has a dull knife, chef B is a noobie but has a very sharp knife. Chef A or B could have a better cut with their current setup, but if the 2 switched setups chef A would most always have the better cut while chef B would blame their setup for the lack of success.

    Having used several different types of equipment at XModdz, i can honest say Hot Air is geared towards smaller components since it is able to be focused using nozzles. IR can be used very well with large BGA due to the heater being very large itself. The Aoyue 732 uses Hot Air & IR, basically air is pushed through the IR plates thus providing heated air as well as convection or radiation to the board. When reworking smaller components the provided nozzles work fine since the thermal mass is low there isnt a lot of problems with uneven heating. When reworking larger BGAs, the nozzles in place would not work well as there would be uneven heating issues, i would remove the nozzle and raise the heater when reworking RSX chips and the temps are usually spot on, the downside is it takes longer to heat since the air flow is not being focused but having an even heat spread more than makes up for that. For smaller BGAs the nozzle in place and low to the component suffices.

    Package temperature is also very important, non ROHS, PB, or lead packages would tolerate a temperature of around 235c, while ROHS, PB free, or lead free packages tolerate temperatures of around 260c. New processors and chipsets use integrated heat spreaders or IHS. It is a heatsink that is affixed semi permantely to the chip. When reworking an RSX chip with Hot Air the package would be much higher than the solder ball temp and this is due to the penetration technology heating up the RSX since it is closer to the heating source and was absorbing much of the heat, applying heat resistant tape to the IHS reduced the temperatures considerably. When reworking with IR the package temp was very close to the solder ball temp due to the absorbtion technology.

    Using the ACHI with stock heaters is basically a terrible system for thick multi layer boards. Not to metion they degrade much quicker. Hot Airving cHot Airnged all 5 plates there is a much more even spread of heat. Reworking thinner boards such as cell phones the stock plates worked fine. Sometimes using the top fan would help with evening out the heat, in some cases it did not make a difference.

    With the ZX 360 station, things were much more complicated and took a very long time to setup, it used a more complicated control system where there were many different settings to be in place. Also Hot Airving come from IR to Hot Air getting used to the air flow system took some time. The recommendations for this machine is to Hot Airve the nozzle very close to the board almost touching it and this is due to the nozzle design. The nozzles Hot Aird a a vent on each side thus having the heat released after penetrating the component instead of creating a humid environment. This is a common design on high end Hot Air rework stations.

    I will end by saying i prefer IR over Hot Air. Unless a manufacturer of machines actually releases an article stating which technology is truly better. I can without a doubt say IR technology is much easier to use than Hot Air. With my IR systems simply modifying the bottom heat 20 degrees higher for thicker boards in the profile was all i needed to achieve a proper rework. Using Hot Air, there was much more involved, raising the top heat as well as having longer dwells and increasing the # of steps to achieve a proper rework.

  3. #3
    Join Date
    Apr 2016
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    3603 Edison Place, Rolling Meadows IL ,USA
    Posts
    2

    Default Re: How to choose rework station BGA

    According to BEST Inc BGA rework station is a repair system to solder and desolder defects during soldering SMD components as empty soldering, short circuit and others. Main differences of rework stations are heat source and heat mode; Take example only upper heat or upper and lower both heating, some can set temperature curve. Considering protecting components, the upper and lower both heating system are better. To prevent PCB warping during repairing, preheat function in the rework system is better. PCB fix, BGA position and others are important consideration. More information at http://www.soldertools.net/bga-stencils-stencilquik/

  4. #4
    Join Date
    Aug 2016
    Posts
    22

    Default Re: How to choose rework station BGA

    This is really a difficult task. Put budget and time constraints on the decision making process. Here are the stages to be consider while choosing the best rework station.
    Deciding criteria, research rework station, justification.

  5. #5

    Default Re: How to choose rework station BGA

    [QUOTE=bgareworkgurl;124285]Choosing a BGA rework station Hot Air vs IR

    [/QUOTE]

    @bgareworkgurl explained it very well. But, also like to share one article which is "Two Prevalent Rework Heating Methods--Which One is Best?" which will also help in choosing the right rework station according to the requirements.


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