ball grid array
A ball grid array, or BGA, is a chip packaging method that uses a grid of small solder balls on the underside of the package to connect it to a circuit board, replacing the perimeter pins used by older package types with connections spread across the entire package surface.
```flowchart
{
"rows": [
{ "type": "nodes", "items": [
{ "title": "Older packages rely on perimeter leads or pins", "sub": "connection count limited by the package's outer edge length", "tone": "neutral" }
]},
{ "type": "arrow" },
{ "type": "group", "title": "BGA spreads solder balls across the whole underside", "items": [
{ "title": "Grid of small solder balls covers the package bottom", "sub": "far more connections fit in the same package footprint", "tone": "blue" }
]},
{ "type": "arrow" },
{ "type": "nodes", "items": [
{ "title": "Many more connections in a compact footprint", "sub": "supports chips needing far more I/O than perimeter pins allow", "tone": "green" }
]}
]
}
```
**BGA packaging exists because perimeter-only connections, like the leads on older package types, run out of room as chips need more and more input/output connections, since only the package's outer edge length limits how many perimeter pins can fit.** As chips have needed increasingly large numbers of connections for power, ground, and signals, BGA packaging addresses the resulting space constraint by spreading solder ball connections across the entire underside of the package rather than only around its perimeter, allowing far more connections to fit within the same compact package footprint.
```svg
```
```svg
```
| Aspect | Perimeter-lead package | Ball grid array |
|---|---|---|
| Connection layout | Around the outer edge only | Across the entire underside |
| Connection density | Limited by edge length | Much higher for same footprint |
| Best suited for | Lower pin-count chips | High pin-count, high-performance chips |
| Common use | Simpler, lower-cost parts | Modern processors and high-I/O chips |
**BGA connection reliability depends heavily on solder ball composition and the board-mounting reflow process, since every one of potentially hundreds of tiny balls needs to form a good connection simultaneously.** Because a BGA package can have hundreds or even thousands of solder balls that all need to form reliable connections at once during the board-mounting reflow process, solder ball material choice and precise control of the reflow temperature profile are both significant factors in overall BGA connection reliability.
**Inspecting BGA solder joints after board mounting is inherently more difficult than inspecting perimeter leads, since the connections are hidden underneath the package rather than visibly accessible around its edge.** Because BGA solder balls sit underneath the package and aren't directly visible once mounted, specialized inspection techniques, such as X-ray imaging, are typically needed to verify solder joint quality, unlike perimeter-lead packages where connections can often be visually inspected directly.
**BGA package variants, including fine-pitch and area-array designs with different ball spacing and counts, let this packaging approach scale to a very wide range of chip I/O requirements.** Because different chips need vastly different numbers of connections depending on their complexity, BGA packaging comes in multiple variants with different ball spacing and overall ball counts, allowing the same fundamental full-area connection approach to scale from modest chips up to the highest I/O count processors.
Read the ball grid array through a checkerboard lens: rather than lining connections up only along a shape's outer border, a checkerboard fills the entire surface with usable squares — a BGA does the same with solder balls, turning the whole underside of a package into usable connection space instead of just its edge.