Solder balls are also called a solder bump or solder sphere, due to their geometry. A solder ball is a spherical piece of soldering used to connect chip packages to PCB.
Solder balls are created through sequential flow/quench or reflow processes. After passing through these processes, they’re then degreased and classified.
You can increase a solder ball’s contact reliability by flattening its ball shape into a coin shape. We call such a solder ball a coin solder ball.
When solder balls are bad news for PCB?
A solder ball can also cause defects in a PCB. They can undermine the electrical reliability of a PCB electronic. Solder balls within 0.13mm of traces, or with a diameter wider than 0.13mm, violate the principle of minimum electrical clearance.
The IPC A 610 standard stipulates that even solder boards that are <=0.13mm in diameter can cause defects. Such defects occur when five solder balls with the stipulated diameter are placed with 100mm^2.
You can inadvertently create detrimental solder balls during automated reflow, as well as during hand soldering. When the solder ball is not warped in the no-clean residue or the conformal coating, it becomes a bane.
However, it could be complicated to determine whether the ball is entrapped in a no-clean residue or conformal coating. However, one natural and reliable way that you can use to determine that is by brush sweeping it.
If it remains in place after you stroke them with a brush, it won’t cause any defects. That’s the IPC’s take on the matter.
There are some other ways to troubleshoot a problematic solder ball. The most effective troubleshooting method first tries to identify the stage where the unintended solder ball occurs.
The defective solder ball can occur either during the printing process, the pick-and-place method, or the reflow process.
Solder balls are integral parts of most consumer electronics. However, as consumers are increasingly demanding smarter, powerful, and portable electronics, it’s become more critical to get it right with solder boards.
However, solder balls remain one of the most complex and delicate components of electric circuitry. Its use requires a high degree of conscientiousness.
How to Make a Solder Ball?
One of the oldest and widely used solder ball creation methods is the 3-Orifice design. In this method, you start by first acquiring a solid solder alloy, preferably an Sn63Pb37 or a Lead-free solder.
Craft the solder alloy into a solder wire or a solder sheet. For a wire, cut the wire into tiny pieces, and for a solder sheet, knock out specks. Cut out pieces and bits in measures that will accurately yield the volume of a solder ball with a 2mm diameter.
Next, place the pieces and specks into a column of hot oil to melt. The upper section of the column of hot crude should have a temperature above the melting point. Moreover, the lower section’s temperature should be below the melting point.
You’ll obtain your desired solder balls when the pieces and specks in the column of hot oil melt. Next, cool the balls in a viscous liquid.
Note that the presence of oxides in the column can distort the spherical shape of the balls. However, you can place a film of flux over the column to prevent this.
This method is highly efficient and low-cost. With this method, you can create up to 7,000 high-quality solder balls per second in any orifice. However, the technique also comes with its downsides.
For starters, the technique can be fraught with contamination and turn out messy. Each of the balls will each have a different weight, although you can measure their values. Also, it’s nearly impossible to obtain balls with a tolerance of 1.5%.
The Importance of The Packaging on The Formed Solder Ball
As noted above, the presence of oxides can distort the shape of the solder ball. One way to prevent the oxidation of the solder balls is through packaging.
Not only can packaging prevent the removal of oxygen, but it can also prolong the shelf-life of the solder balls even beyond their expiry date.
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