First-Aid Kits for Circuit Boards ®
Newsletter | Ordering | Login
Phone: 978-373-1600
  
Exploding Solder Balls More Features
Exploding Solder Balls
Figure 1: Typical BGA pad with extending "dog bone" style via.
Manufacturers solder tens of thousands of BGA components every day. Most of this activity occurs in the flow of manufacturing and some during rework. Most BGA placement is performed flawlessly. On the other hand, industry's dynamic forces constantly push the envelope. Occasionally things go wrong.

Circuit board designers are continuously looking for more real-estate. That can be as difficult as looking for apartments in Manhattan, but that doesn't stop them from searching.

It used to be that BGA pads were always routed out to a via on the same side of the board as the pad. Now more and more designers are trying to reclaim that space by using the BGA pad itself as a via. See Figures 1 and 2.

Exploding Solder Balls
Figure 2: BGA via-in-pad arrangement.
There are occasions when the via in pad solution causes disruptions in BGA placement. There are a number of different issues that are addressed on various technical forums, but today we'll only address one; filled vias.

Densely spaced BGA locations present numerous challenges for placement. The thermal and electrical characteristics must be carefully calculated and balanced. At a minimum, when the board is exposed to solder reflow temperatures the site must remain stable.

In a recent case a customer was experimenting with a variety of different fill materials. Variance and voiding in the fill material caused failures in BGA placement. The T sub g variance at one large BGA site caused the board to warp at that location. The warping problem was addressed and solved, but the voiding issue remained.

Exploding Solder Balls
Figure 4: Void has caused the side of the BGA ball to "blow out" and deposit debris.
Exploding Solder Balls
Figure 3: BGA ball void aggravated by gases escaping from via in pad.
What's the problem with voiding you ask? Theoretically, if voids were stable during the thermal transients of BGA rework, there would be no problem, but this is a case where common sense dictates that there will be dynamic forces at work once these voids are exposed to rework temperatures.

The via is like a long tower with a ball placed on its top. Figure 3 shows what can happen when some of those via voids rise up into the BGA sphere. BGA voiding is a condition that is battled by rework personnel without the presence of integral via voiding. So adding the via void factor to the rework equation can only aggravate the condition, sometimes with disastrous results.

Figure 4 is a picture of a void that was so volatile that it caused the BGA ball to "blow out". It blew out so forcefully that it deposited a loose piece of solder under the BGA.
Several members of the Circuit Technology Center team contributed to this feature story.
Are Your BGA Rework Techs Competent?
Are Your BGA Rework Techs Competent?
Can every operator handle your BGA rework equally well? In real life, in all but just a few situations, the answer is no. Why is this so?
Learn more ...
11 Rules for Circuit Board Mods
11 Rules for Circuit Board Mods
Some of the odd twists and turns occasionally needed to modify assembled circuit boards can be surprising. Discover the 11 rules your techs should know.
Learn more ...
Must Have Circuit Boards First-aid Kits
Must Have Circuit Boards First-aid Kits
These kits have been used for decades by the most demanding electronics manufacturers. Every item is thoroughly field tested.
Learn more ...
Can You Repair a Broken Corner?
Can You Repair a Broken Corner?
What happens to an assembled circuit board with a broken corner? Can it be repaired reliably? It can if you have the training and the experience.
Learn more ...
Challenging Surface Mount Pad Repair
Challenging Surface Mount Pad Repair
Surface mount and BGA pad repair are routine operations at Circuit Technology Center. Learn how it's done with absolute precision and reliably.
Learn more ...
Do Your Repair Techs Deserve One?
Do Your Repair Techs Deserve One?
The Micro-Drill is the ideal tool for precision drilling, grinding and cutting on circuit boards. Use it to remove coatings, cuts circuits, drills holes, and much more.
Learn more ...
87 Repair/Rework Guides Free Online
87 Repair/Rework Guides Free Online
This free online guidebook, packed with detailed illustrations, will be helpful to anyone who needs to repair or rework circuit board assemblies.
Learn more ...
BGA Component Rework Simplified
BGA Component Rework Simplified
When you have tough BGA rework, where do you turn to? Discover the nation's #1 contractor for outsourced BGA rework, repair and reballing.
Learn more ...
Stop PCB Scrap Today
Stop PCB Scrap Today
What happens to your valuable circuit boards when they're damaged? Can they be repaired reliably and cost-effectively? Yes, if you have the skills and knowhow.
Learn more ...