A PGA socket connects a pin grid array device to a board through the device’s underside pins, with no soldering of the device itself. Three parameters decide which socket fits: pin count, pin pitch, and how much force the pins survive during insertion. Zero insertion force (ZIF) sockets clamp the pins with a lever or cam, low insertion force (LIF) sockets lighten the seating force without an actuator, and standard friction sockets grip each pin directly.

Key takeaways

• Fix pin count and pitch first, then choose insertion force and durability to match the device and the number of insertions.
• Standard pitch is 2.54 mm (0.100 in); fine-pitch PGA and most test sockets use 1.27 mm (0.050 in).
• Move to ZIF above roughly 100 to 200 pins, or whenever a device is inserted more than a few times, because friction sockets bend fragile pins on high-count parts.
• AMD used PGA on mainstream desktop CPUs through Socket AM4 at 1331 pins; AM5 switched to LGA, and Intel moved to LGA at LGA775 in 2004.
• For test and burn-in, specify gold-over-nickel contacts, a high-temperature housing, and rated insertion cycles in the thousands.

What a PGA socket does

A pin grid array places the package pins on the underside in a regular matrix. The socket receives those pins and routes each one to the board, so the device stays removable for service, upgrade, or test. This separates PGA from BGA, where solder balls fix the device permanently, and from LGA, where the package presents flat lands and the spring contacts live in the socket.

The practical consequence is mechanical. PGA pins are thin and easy to bend, so the socket has to seat and retain them without shearing them. That constraint drives the split between friction, LIF, and ZIF designs.

ZIF, LIF, and standard sockets: insertion force decides pin survival

A ZIF (zero insertion force) socket uses a lever or screw cam to open its contacts, so the device drops in with almost no force and then clamps for a firm connection. A LIF (low insertion force) socket has no actuator; it applies lighter contact force than a standard friction socket, trading some retention for safer seating.

[IMAGE 1: cross-section of a ZIF socket showing the lever cam opening the contacts around a PGA pin | alt: “ZIF PGA socket cross-section showing a lever cam clamping a pin grid array pin”]

Standard friction sockets give the firmest grip and the lowest cost, but the per-pin insertion force adds up. On a 300-pin device that force can fold pins before they align, which is why friction sockets stay on low-count parts that seat once. LIF reduces that risk for moderate counts and occasional service. ZIF removes it: the contacts stay open until the device is fully seated, then the lever closes them with a controlled wipe.

Property	Standard (friction)	LIF	ZIF
Insertion force	Full, per pin	Reduced	Near zero, lever or cam actuated
Actuation	None	None	Lever or screw cam
Typical pin counts	Up to ~100	~40 to 200	100 to 1300+
Reinsertion cycles	Few (units)	Tens	Hundreds to thousands
Pin protection	Poor on high counts	Moderate	Excellent
Contact-R stability	Good if gold	Good	Good, actuation controls wipe
Board space	Compact	Compact	Needs lever swing clearance
Relative cost	Lowest	Low to mid	Highest
Typical use	Low count, seat once	Field service, moderate count	CPUs, ATE, burn-in, high count

Pin pitch and grid layouts

Classic PGA uses a 2.54 mm (0.100 in) grid, the same pitch as through-hole DIP parts, which is why early sockets reused mature contact technology. Denser devices drop to 1.27 mm (0.050 in), and micro-PGA CPU sockets went finer still to fit hundreds of pins under a small lid.

Layout matters as much as pitch. A full grid populates every position, while a depopulated or perimeter grid leaves the center open for a cavity or to cut pin count. SPGA (staggered pin grid array) offsets alternate rows by half a pitch, which packs more pins into the same footprint and appeared on Socket 5 and Socket 7 parts. Pins are addressed by a row-letter and column-number matrix, so a bent A1 pin is easy to call out on an inspection report.

[IMAGE 2: side-by-side diagram of a full grid versus a staggered pin grid array (SPGA) layout | alt: “Full grid versus staggered pin grid array SPGA pin layout comparison”]

PGA package sub-types you will meet

The substrate under the pins sets cost, thermal path, and reliability. The names below describe the same pin-grid idea built on different materials or in a different layout.

Sub-type	Substrate	Notes	Example era or use
CPGA	Ceramic	High reliability, tolerates high temperature	Older CPUs, mil and aero
PPGA	Plastic	Lower cost, modest thermal path	Celeron, Socket 370 era
FC-PGA	Flip chip on organic or ceramic	Die mounted face down for better thermal and electrical path	Pentium III and Pentium 4 era
OPGA	Organic	Cost and performance balance	Some Athlon parts
SPGA	Layout, not a substrate	Staggered rows raise pin density	Socket 5 and Socket 7

Historical CPU sockets as a pin-layout reference

CPU sockets are the most documented PGA parts, so they make a useful sizing reference even for non-CPU work. The pin counts below are stable historical facts; confirm exact pitch and package revision against the platform datasheet before you commit a footprint.

Socket	Pins	Pitch	Package	Actuation	Era
Socket 7	321	2.54 mm	SPGA	ZIF lever	Pentium
Socket 370	370	2.54 mm	PPGA / FC-PGA	ZIF lever	Pentium III
Socket A (462)	462	2.54 mm	CPGA / OPGA	ZIF lever	Athlon / Duron
Socket 478	478	verify (mPGA)	FC-PGA	ZIF lever	Pentium 4
Socket AM4	1331	verify (mPGA)	mPGA	ZIF cam	Ryzen (to 2022)

[IMAGE 3: underside pins of a PGA CPU next to the flat lands of an LGA socket, each labeled | alt: “PGA package pins compared with LGA socket contacts”]

The industry split is worth remembering. AMD kept the pins on the CPU (PGA) for mainstream desktop through AM4, then moved to LGA on AM5, while Intel moved the pins into the socket (LGA) at LGA775 in 2004. If a part is called LGA, the fragile pins are in the socket rather than on the device, and the handling rules invert.

Contacts, plating, and current

Socket springs are usually beryllium copper or phosphor bronze. Beryllium copper holds its contact force better at temperature, so burn-in and high-temperature sockets favor it. Plating decides electrical life, since gold over nickel gives low, stable contact resistance and tolerates many insertions, whereas tin costs less but oxidizes and suits permanent, seat-once sockets.

Typical figures for signal-grade sockets sit in the tens of milliohms for contact resistance and around 1 A per contact, with power contacts rated higher. Gold thickness is commonly quoted from about 0.38 to 0.76 µm (15 to 30 µin) over a nickel underplate. Treat these as starting points and confirm the exact contact resistance, current rating, and plating on the specific series, because they vary widely across friction, LIF, ZIF, and test sockets.

How to choose: a selection decision path

1. Get the package drawing first: pin count, pitch, grid map, and pin length and diameter.
2. Count expected insertions over the product or test life; more than a few points to LIF or ZIF.
3. If pin count exceeds roughly 100 to 200, default to ZIF to avoid bent pins on seating.
4. Set the thermal environment, since burn-in or high ambient favors beryllium copper contacts and an LCP or PPS housing rated to your temperature.
5. Set electrical needs, because high-speed test favors spring-probe or elastomeric sockets over long-pin sockets; check contact inductance and capacitance against your signal bandwidth.
6. Set durability, as test and ATE work needs rated cycles in the thousands and gold plating.
7. Set mounting: choose through-hole solder, press-fit, or clamshell, and confirm lever swing clearance in the board layout.
8. Confirm compliance last: RoHS and REACH on materials and plating, and UL94 V-0 flammability on the housing.

Failure modes and how to avoid them

• Bent or sheared package pins from friction insertion on high-count parts. Move to ZIF and inspect the grid map for the pins most exposed during misalignment.
• Rising contact resistance as gold wears through to nickel over many cycles. Specify adequate gold thickness and a rated cycle life for the duty.
• Open or intermittent contacts from tin oxide or debris. Use gold plating for reworkable and test sockets and keep the contact area clean.
• Contact force relaxation at high temperature. Prefer beryllium copper over phosphor bronze for burn-in and hot environments.
• Solder joint fatigue on high-pin-count through-hole sockets under thermal cycling. Control the reflow or wave profile and add mechanical retention.
• Intermittent contact on large arrays from package warpage or socket coplanarity. Hold a flatness spec and use a proper loading mechanism.

Suppliers and where they fit

Several suppliers specialize in PGA and pin-grid test sockets, including Aries Electronics, Yamaichi, Enplas, Plastronics, Ironwood Electronics, 3M (Textool ZIF), Mill-Max, Loranger, Winslow, Preci-Dip, and Amphenol. Some lean toward production sockets and others toward ATE and burn-in. Pull the exact series and part number from a distributor listing and confirm the pin count, pitch, plating, temperature range, and cycle life against the datasheet before you order.

Frequently asked questions

What is a PGA socket?

A PGA socket is a receptacle that connects a pin grid array device to a circuit board through the device’s underside pins, without soldering the device down. It keeps the part removable for upgrade, service, or test, and comes in friction, low insertion force, and zero insertion force styles.

What is the difference between ZIF and LIF sockets?

A ZIF socket has a lever or cam that opens the contacts, so the device seats with almost no force and is then clamped. A LIF socket has no actuator and simply uses lighter contact force than a standard socket. ZIF protects fragile high-count parts and supports many insertions, while LIF suits moderate counts and occasional service.

What does zero insertion force mean?

Zero insertion force means the socket contacts stay open while the device is placed, so no force acts on the pins during seating. A lever or screw then closes the contacts onto the pins. This prevents bent pins on high pin-count devices and allows repeated insertion for test and rework.

Are PGA sockets still used?

Yes, though less in new consumer CPUs. AMD used PGA on mainstream desktop through Socket AM4 and moved to LGA on AM5, and Intel has used LGA since 2004. PGA and pin-grid sockets remain common in test and burn-in, in legacy and industrial systems, and in some FPGA and processor prototyping.

What pin pitch do PGA sockets use?

The standard PGA pin pitch is 2.54 mm (0.100 in), matching through-hole DIP spacing. Denser devices use 1.27 mm (0.050 in), and micro-PGA CPU sockets went finer to fit hundreds of pins. Always confirm the pitch and grid map on the package drawing before selecting a socket.

Is a PGA socket the same as an LGA socket?

No. In a PGA system the pins are on the device and the socket receives them. In an LGA system the package has flat lands and the spring pins live in the socket. The two are not interchangeable, and they reverse which part carries the fragile contacts, so handling and inspection differ.

What to do next

Choose ZIF for any high-count or repeatedly inserted PGA device and for all test and burn-in work, and reserve friction sockets for low-count, seat-once parts where cost and board space matter and pin stress is not a concern. Size the contact plating and housing temperature to the actual duty cycle rather than the nominal part rating, then verify pin count, pitch, current, plating, and cycle life against the chosen series datasheet before release.