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underfilling of bga

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#58834

underfilling of bga | 18 May, 2009

Dear All,

Does anyone on the forum have experience with underfilling process of bga? We have a component with 0.5mm bga on one of the new products. Customer wants this component to have an underfill.

Questions - 1) which kind of epoxy or chemicals can be used 2) Is the manual application of an underfill recommended for such packages or must i use an automated machine

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#58841

underfilling of bga | 19 May, 2009

whats the reason for the underfill? we dont underfill any of our BGAs

rework could be a issue if they need to be replaced?

tried DP190?

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#58842

underfilling of bga | 19 May, 2009

Search the fine SMTnet Archives to find threads like: http://www.smtnet.com/forums/Index.cfm?CFApp=1&Message_ID=58257

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CL

#58843

underfilling of bga | 19 May, 2009

Good Morning,

We are underfilling some of our BGA's. This is a specified customer requirement. The material we are using is Emerson & Cuming E-1216 (also specified by the customer) The material was selected because of a close CTE match with the PCB. We are applying using a manual process. I agree that underfill is a rework concern. we have had a few assemblies fail fuctional test and have been unable to remove the material cleanly to allow any rework. All of this needs to be considered at quote.

Good Luck

Chris

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#58872

underfilling of bga | 22 May, 2009

Depending on the material chosen, it's possible to �rework� underfilled components. However, it's far from a production process. Two steps are usually required. First: remove the package from the PCB. Second: remove the residual underfill from the PCB. Neither step is without its problems. Typically the underfill forms a seal around the component as well as being drawn between component and PCB by capillary action. If the material can be heated to a plastic state to become vicious, a gripper tool, combined with a shear movement, can be used to pry the package from the PCB. Under some circumstances the bead will need to be removed first � using a knife tool, followed by the heating phase. Once removed, some form of mechanical or etching process will be needed to remove the residual underfill material from the PCB. Depending on the value of component and PCB this may not be deemed a viable production process!

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#58873

underfilling of bga | 22 May, 2009

Henkel- Hysol seems to be the most popular material that I see:

http://www.henkel.com/cps/rde/xchg/SID-0AC83309-B331D246/henkel_com/hs.xsl/12169_20090505-henkel-launches-next-gen-underfill-20681_COE_HTML.htm

As far as application method, its all about production rate and accuracy & repeatability requirements. You can do it manually, but as with most operations, machines to it better and faster. Here are some underfill dispensing machines:

http://www.speedlinetech.com/process.aspx?ProcessId=17

http://www.asymtek.com/applications/underfill.htm

http://www.newport.com/store/genproduct.aspx?id=478095&lang=1033&Section=Spec

http://www.gpd-global.com/

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stevenlimth

#59175

underfilling of bga | 1 July, 2009

1smtdude, I interested in your explaination of re-work an underfill part. You mention the material can be heated to a plastic state to become vicious... do you know usually what range is the temperate? (guess it can depend on the type/manufacturer of the underfill also?)

thanks

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#59289

underfilling of bga | 14 July, 2009

> 1smtdude, I interested in your explaination of > re-work an underfill part. You mention the > material can be heated to a plastic state to > become vicious... do you know usually what range > is the temperate? (guess it can depend on the > type/manufacturer of the underfill also?) > thanks

of course the temperature range depond on the type of the underfill.

fisrtly the temperature should be higher than the melting point of the solder ?as we know Pb or Pb-free solder is quite different)? secondly?As I know if the type of underfill is epoxy, the rework temperater usually from 230-270 degrees?the actual temperature of the solder joints??Lastly?higher temperture may be good to rework process, but it also may be damage to the pcb or the component. So we should get a balance between them.

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#59293

underfilling of bga | 15 July, 2009

Depending on the end use of the PCB, edge or corner bonding may be adequate. Much easier to rework as the material is only at the perimeter of the part. We don't do underfill of any degree in-house but a few years ago we did build a limited run of experimental boards for a customer (a very fussy one!) where they *insisted* that all of the devices (DDR2s and other uBGAs) were underfilled. We talked them into settling for edge bonding even though we felt it unnecessary for the end use environment.

We rented a tabetop dispenser from a popular dispensing supplier which was loud and messy. The material we used was Loctite 3129.

Good luck.

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#61407

underfilling of bga | 19 March, 2010

There is a wide range of BGA underfills to satisfy specific needs. Some are designed for those who place a premium on high speed, high volume processing, shock or drop test perforamnce, and ease of reworkability. Others are designed for those who place a premium on thermal cycle performance, sacrificing process speed and/or reworkability. All can be dispensed either manually or automatically.

One company that has a portfolio of BGA underfills, and edgebond adhesives, that span a wide range of requirements is Zymet, http://www.zymet.com.

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#61409

underfilling of bga | 19 March, 2010

Rework is typically done by heating the BGA to 170-180C to first scrape off the fillet. Then, heat to above reflow, and lift the BGA. Then, collapse the solder with heat and flux. Then, back down at 170-180C, scrape off the underfill from the board. Then, re-dress the pads. Exact conditions and process can vary from one underfill and the next.

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PCB Soldering Tools

Non-heated dispensing system