A PGA, or pin grid array, is an IC package with pins arranged in a regular grid on the underside, mounted by inserting those pins into a socket or a through-hole board. The body is square or rectangular, the pins are commonly on a 2.54 mm (0.1 in) or 1.27 mm (0.05 in) grid, and counts run from a few dozen to over 1,300. PGA was the dominant high-pin-count CPU package for two decades before land grid array and ball grid array took over. This is what the package is, its variants, and how it compares.
Key takeaways
- A PGA has pins on the chip that plug into a socket, so the part is removable — the trait that made it the desktop CPU package for decades.
- Pins sit on a regular grid: 2.54 mm (0.1 in) on standard PGAs, 1.27 mm (0.05 in) on high-count micro PGAs, and 1 mm on Intel’s reduced (rPGA) mobile parts (Wikipedia, pin grid array).
- Variants differ by substrate and die attach: ceramic (CPGA), plastic (PPGA), organic (OPGA), and flip-chip (FC-PGA), plus staggered (SPGA) and reduced-pitch (rPGA) layouts.
- Pin counts scale from tens on early parts to 1,331 on AMD’s Socket AM4 — the last mainstream desktop PGA before AMD moved to LGA with AM5.
- PGA versus LGA versus BGA is a question of pins, lands, or balls: PGA and LGA socket and are serviceable; BGA solders and is permanent.
- New designs rarely use PGA. It survives in legacy desktops, some mobile sockets, and hermetic ceramic parts for aerospace and military.
What the PGA package is
A pin grid array is a square or rectangular IC package with rigid pins projecting from the bottom in a grid. Flip one over and it looks like a bed of nails. The pins carry signal, power, ground, and sometimes alignment functions, and the center of the array is usually left open as a chip cavity where the die sits.
The defining feature is that the pins go into a socket, not solder. Drop a PGA into a zero-insertion-force (ZIF) socket, close the lever, and it is held without a soldered joint, which means it pops out and swaps in seconds. That interchangeability is why the PC industry built processors around PGA for so long — a CPU could be upgraded or replaced without touching an iron.
PGA earns its keep on pin count. It fits far more connections than a dual in-line package, and it did so before surface-mount packages matured, which is how processors reached hundreds of pins in the 1980s and 1990s. The trade-off is mechanical: the pins are thin and bend, and the package is bulky next to modern surface-mount parts.
[IMAGE 1: Underside and cross-section of a PGA package showing the pin grid, chip cavity, and die | alt: “PGA package pin grid array underside chip cavity cross-section”]
How a PGA is built
Every PGA is a substrate with pins on the bottom and a die on top, but the substrate material and the way the die attaches vary, and those two choices define most of the named variants.
The substrate is ceramic, plastic, or organic laminate. Ceramic (alumina) is hermetic, thermally stable, and expensive, which suits aerospace and military use. Plastic and organic laminate are cheaper and lighter, which suited high-volume consumer CPUs once cost mattered more than a hermetic seal.
The die attaches by wire bonding or flip-chip. In a wire-bonded PGA the die sits face-up and thin wires connect it to the substrate. In a flip-chip PGA the die is bumped, flipped face-down onto the substrate, and its back is left exposed for a heatsink — the arrangement Intel used on the FC-PGA. Flip-chip shortens the electrical path and improves cooling, which is why later, faster parts moved to it.
PGA pitch and pin count
Two numbers describe any PGA: the pin pitch and the pin count. Pitch is the grid spacing; count is how many pins fill it.
Standard PGAs use a 2.54 mm (0.1 in) grid. Higher-count parts drop to a 1.27 mm (0.05 in) micro grid to fit more pins in the same area, and Intel’s mobile reduced pin grid array (rPGA) went to 1 mm (Wikipedia, pin grid array). Below are verified anchors across the range.
| Package / socket | Pins | Pin pitch | Body / note |
| Socket 370 (Intel FC-PGA) | 370 | 2.54 mm, staggered | 49.53 mm sq; pins φ0.43–0.48 mm × 3.05–3.30 mm |
| Socket 478 (Intel mPGA478B) | 478 | 1.27 mm, regular | 36.5 mm sq; pins 2.03 mm long |
| Socket A / 462 (AMD) | 462 | micro / staggered | 49.53 mm sq; Athlon, Duron |
| Socket AM4 (AMD) | 1331 | 1.27 mm class | last AMD desktop PGA |
| µPGA interposer (Intel) | 495 / 615 | 1.27 mm | mobile OLGA carrier |
| Socket G2 (Intel rPGA) | 988 | 1.00 mm | mobile Core i |
The count climbed steadily. Early ceramic PGAs carried dozens to a couple hundred pins; Intel’s Socket 370 held 370 on a staggered 2.54 mm grid; Socket 478 packed 478 on a 1.27 mm grid in a smaller body; and AMD’s Socket AM4 reached 1,331 pins before the format gave way to LGA. Note that the center chip cavity means the pins do not cover the whole underside.
PGA package types
The PGA family splits into variants named for substrate, die attach, or pin layout. They are not mutually exclusive — a part can be an organic, flip-chip, micro-pitch PGA at once — but each term pins down one property.
| Subtype | What defines it | Die attach | Example |
| CPGA (ceramic) | ceramic substrate; hermetic; high-temp | wire-bond | 1st-gen Intel Pentium; AMD Socket A (early) |
| PPGA (plastic) | plastic substrate; low cost | wire-bond | Mendocino Celeron (Socket 370) |
| OPGA (organic) | organic laminate substrate | wire-bond / flip-chip | AMD Athlon XP (Socket A) |
| FC-PGA / FC-PGA2 | flip-chip die; back exposed or IHS | flip-chip (C4) | Intel PIII / P4 (Socket 370/478) |
| mPGA / µPGA (micro) | reduced 1.27 mm pitch | any | Socket 478; AMD Socket A–AM4 |
| SPGA (staggered) | offset rows for higher density | any | Socket 5/7; Socket 370 |
| rPGA (reduced) | 1 mm pitch (mobile) | flip-chip | Intel mobile Core i (Socket G1/G2) |
Two naming notes. SPGA almost always means staggered pin grid array, where alternate rows are offset so pins pack closer than a square grid allows; it is the layout Socket 5, Socket 7, and Socket 370 used for high pin counts. And “micro” (mPGA), or the AMD spelling µPGA, denotes the 1.27 mm reduced pitch, not a different construction. For the flip-chip and micro variants specifically, see the dedicated FC-PGA and mPGA references.
[IMAGE 2: Montage of CPGA, PPGA, OPGA, and FC-PGA packages showing substrate and die differences | alt: “PGA types CPGA PPGA OPGA flip-chip package comparison”]
PGA vs LGA vs BGA
The three grid-array families differ in one thing: what sits on the bottom of the package. PGA has pins, LGA has flat lands, and BGA has solder balls. That single choice drives everything else.
| Aspect | PGA | LGA | BGA |
| Board contact | pins on the chip | flat lands on the chip | solder balls on the chip |
| Mates to | socket holes (ZIF) | socket spring pins | soldered PCB pads |
| Serviceable | yes (pops out) | yes (unclamp) | no (rework only) |
| Relative density | moderate | high | highest |
| Fragile part | CPU pins | socket pins | none (but permanent) |
| Typical use | legacy desktop, mil/aero | current desktop CPUs | mobile, embedded, FPGAs |
The practical split is socketed versus soldered. PGA and LGA both drop into sockets and can be removed — PGA puts the fragile pins on the CPU, LGA moves them into the socket, so an LGA CPU survives a drop but a bent socket pin can scrap a motherboard. BGA reflows onto the board and is effectively permanent, trading serviceability for the highest connection density, which is why phones, embedded systems, and modern FPGAs use it.
PGA sockets and how they mount
Most PGAs mount in a ZIF socket. The pins are aligned by hand, dropped in with no force, and locked by a single lever that shifts the contacts sideways to grip each pin. Actuation is light by design — Intel’s mPGA478 socket caps the lever force at 4.5 kg — because the pins cannot take much side load.
Older and lower-count PGAs were also soldered directly into plated through-holes, the same as a large DIP, where interchangeability was not needed. Either way, the pins pass through or into the board rather than sitting on the surface, which is what makes a PGA a through-hole-class part in a surface-mount world.
Keying matters. A PGA is designed to seat one way, marked by a pin-1 corner, a missing or plugged pin, or a chamfer. Same-size sockets are often electrically incompatible, so the pin-count number is not a guarantee of fit.
Where PGA is used today
PGA is mostly a legacy format. Intel’s last desktop PGA was Socket 478; every Intel desktop socket since has been LGA. AMD held onto pins far longer, through Socket AM4 and its 1,331-pin parts, then switched to LGA with Socket AM5 in 2022. On the logic side, high-pin-count FPGAs and ASICs moved to BGA years ago for density.
Where PGA still ships new, it is usually ceramic. Hermetic ceramic PGAs — and their column-grid cousins, CCGA, which swap pins for high-lead solder columns — remain in aerospace, radiation, and military hardware, where a sealed, temperature-stable package outweighs cost and density. For mainstream design, though, meeting a PGA now means servicing or upgrading existing hardware more often than specifying a new part.
Handling and design notes
The failure mode to respect is bent pins. A dropped PGA or a careless insertion folds pins, and a micro-pitch pin is far harder to straighten than a coarse one. Align the pin-1 mark to the socket, seat the part flat, and let the ZIF lever do the work rather than pressing on the package.
For sourcing, check availability against the exact part and socket. PGA is often the first package a manufacturer discontinues, and a design tied to a socketed CPU can strand if the part goes end-of-life. When matching a replacement, confirm the socket designation and keying, not just the pin count, since mechanically similar sockets can be electrically different.
Frequently asked questions
What does PGA stand for?
PGA stands for pin grid array. It is an IC package with pins arranged in a regular grid on the underside, inserted into a socket or through-hole board. The body is square or rectangular, pins are usually on a 2.54 mm or 1.27 mm grid, and the format is used mainly for processors.
What is the difference between PGA and LGA?
PGA puts the pins on the chip, which plug into holes in the socket. LGA puts flat contact lands on the chip and moves the pins into the socket. LGA fits more contacts and gives a more durable chip, but a bent socket pin can ruin the motherboard; PGA keeps the fragile pins on the replaceable CPU.
What is the difference between PGA and BGA?
PGA has pins that socket, so the chip is removable. BGA (ball grid array) has solder balls that reflow onto the board, so the chip is permanent and needs rework equipment to change. BGA reaches higher density and better electrical performance; PGA is serviceable.
What are the types of PGA packages?
The main types are CPGA (ceramic), PPGA (plastic), and OPGA (organic), named for substrate, plus FC-PGA (flip-chip die attach), mPGA or µPGA (1.27 mm micro pitch), SPGA (staggered rows), and rPGA (1 mm reduced pitch). A single part can combine several, such as an organic flip-chip PGA.
What is the pin pitch of a PGA package?
Standard PGAs use a 2.54 mm (0.1 in) pin pitch. High-pin-count parts use a 1.27 mm (0.05 in) micro pitch, and Intel’s mobile reduced pin grid array (rPGA) uses 1 mm. The pitch is the center-to-center spacing of the pins in the grid.
Is PGA still used?
Rarely for new designs. Intel desktop moved to LGA after Socket 478, AMD after Socket AM4, and FPGAs to BGA. PGA survives in legacy desktop upgrades, some mobile sockets, and hermetic ceramic parts for aerospace and military, where a sealed, socketable package is worth the cost.
Bottom line
Reach for the PGA concept when you are identifying a socketed processor, comparing CPU sockets, or working on legacy or high-reliability hardware — not when specifying a new mainstream part, which will be LGA or BGA. Read the package by its bottom: pins mean PGA and a socket, lands mean LGA, balls mean BGA and solder. If it is a PGA, note the pitch (2.54 mm or 1.27 mm), respect the pins, match the exact socket and keying, and check that the part is still stocked before you commit.
[IMAGE 3: Side-by-side undersides of PGA (pins), LGA (lands), and BGA (balls) | alt: “PGA pins versus LGA lands versus BGA balls underside comparison”]
External primary sources
- Wikipedia — Pin Grid Array (pitch and variants): https://en.wikipedia.org/wiki/Pin_grid_array
- Texas Instruments — Pin Grid Array (PGA) package family: https://www.ti.com/packaging/docs/searchtipackages.tsp?packageName=PGA
- Intel 2000 Packaging Databook, Chapter 13 (FC-PGA / PPGA / µPGA): https://www.intel.de/content/dam/www/public/us/en/documents/packaging-databooks/packaging-chapter-13-databook.pdf
- Intel Pentium 4 478-Pin Socket (mPGA478) Design Guidelines: https://download.intel.com/design/Pentium4/guides/24989002.pdf
