Thanks for the inputs Wayne.

Yes I am speaking about a product that got  a lot of interest about 15 years ago.

It would have enough fluxing activity to solder a bump to a pad and the residues would set-up and encapsulate the bumps.



Rich  Kraszewski

Senior Staff Process Engineer

Phone: (920) 969-6075



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From: Wayne Thayer [mailto:[log in to unmask]]

Sent: Monday, June 15, 2020 12:29 PM

To: TechNet E-Mail Forum <[log in to unmask]>; Richard Kraszewski <[log in to unmask]>

Subject: Re: [TN] Reflow Encapsulant Availability





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Hi Rich-



I'm unfamiliar with this type of product. Are you sure you are talking about encapsulation, or are you thinking "underfill".



The "usual way" of making a BGA-based module which can be reflowed is to first underfill the BGA. That is very complicated to implement. For low quantity stuff, where you can't do the massive qualification necessary to get the underfill process fully validated, most of us just let the BGA reflow with no encapsulation or underfill.



Trying to get away without full qualification of the underfill process will lead to much misery. The underfill system includes:



  *   The material on the bottom of the BGA

  *   The soldermask on the PCB the BGA is reflowed to

  *   Flux chemistry

  *   Cleaning chemistry and effectiveness

System failure usually results in a tiny crack opening up at either the BGA surface or the PCB soldermask. The underfill mechanical characteristics at high temperatures usually ends up causing pressure on the molten solder. This molten solder then flows into the cracks and creates amazing shorts that are very difficult to see on X-Ray inspection.



Even just getting proper underfill flow and cure can be a big job. Several years ago I was responsible for a line doing this and learned that incredibly small amounts of moisture in the PCB material can force its way into the underfill chemistry because of the captured volume beneath the BGA. The result is a new substance that has no redeeming qualities for the underfill situation!



Good Luck!



Wayne Thayer



On Mon, Jun 15, 2020 at 8:16 AM Richard Kraszewski <[log in to unmask]<mailto:[log in to unmask]>> wrote:

I have a potential need for a reflow encapsulant for a BGA

Had reached out  to Henkel  but was informed that they had  discontinued that  product line.

Anyone have a different source?



Rich  Kraszewski

Senior Staff Process Engineer

Plexus



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