US OSAT — OUTSOURCED SEMICONDUCTOR ASSEMBLY & TEST
A US OSAT built for low-volume work.
Heisler Semiconductor operates as a US-based OSAT — an outsourced semiconductor assembly and test provider — in Halethorpe, Maryland. We run prototype and low-to-mid-volume advanced-packaging programs: die attach, wire bond, flip chip, hermetic sealing, inspection, and test, on US soil.
Programs here start as small as one unit — a first article, a DOE lot, a pilot build — and scale on the same line to production runs at 3,000 components per hour per system, on multiple automated systems. If your quantity has ever been turned away as too small for an assembly line, this is the page for you.
/ US-soil assembly / prototype quantities / prototype-to-volume / engineer-to-engineer
WHAT AN OSAT IS
Assembly and test, outsourced.
An OSAT takes finished die from a foundry or a die bank and delivers packaged, tested parts. Heisler is the low-volume, US-based version of that model: the die are yours, the packaging engineering and the line are ours.
- A US OSAT: outsourced semiconductor assembly and test performed on US soil, by a domestic engineering team.
- A services provider — engineering, assembly, inspection, and packaging, from design-rule review through qualified volume.
- Built for prototype quantities and low-to-mid-volume programs — with automated placement at 3,000 components per hour per system when a program scales.
- Not a foundry and not an IDM — we do not fabricate wafers or die.
- Not a chip designer or a fabless product company — we do not sell our own chips.
- Not a commodity high-volume line — a locked, million-unit design belongs on one; a program still being engineered belongs here.
PROCESS COVERAGE
Every process, one roof.
The processes below run in one facility, under one quality system. Each links to its full capability page.
3D heterogeneous integration
Multi-die stacking, interposers, fan-out WLP, and chiplet integration.
Wafer-level processing
Direct-write litho, TSV, deposition, etch, and RDL for interposers and WLP.
Laser micromachining
Micro-via drilling, dicing, singulation, and marking on Si, sapphire, ceramics, and metals.
Inspection & metrology
X-ray, 3D AOI, SEM, and cross-section — the traceable data record for every build.
Failure analysis & reliability
Thermal cycling, hermeticity test, screening, and cross-section FA.
LOW-VOLUME BY DESIGN
Prototype quantities are the point.
Most assembly houses treat low volume as an interruption to a high-volume schedule. Heisler is organized around it: prototype quantities, engineering lots, and pilot builds are the schedule.
A one-piece first article runs the same line, the same inspection gates, and the same per-build traveler discipline as a pilot run. That matters because the first article is where the process window gets proven — and the proof is only worth something if the volume build inherits it.
That inheritance is the prototype-to-volume model: build a test vehicle, run the DOE, prove the window, then scale the same process on the same line — no re-qualification handoff to a separate volume supplier, no second supplier re-learning your part.
Evaluating suppliers for a program like this? Work through the seven-criteria framework in Choosing a US OSAT. A fabless team with a taped-out chip should start at ASIC Packaging & Test.
WHO RUNS LOW-VOLUME PROGRAMS
Industries that run small.
Low-volume, high-consequence hardware is concentrated in a few markets — and each has its own packaging page.
- Aerospace & defense — qualification-driven builds where the program, not the unit count, sets the bar.
- Medical & bio — implantable and diagnostic devices that start at prototype quantities and stay traceable.
- RF & mmWave — GaN, GaAs, and AlN assemblies where the package is part of the circuit.
- Advanced sensors — MEMS, biosensor, and microfluidic die that need sensor-grade handling.
FAQ
Answers, before you ask.
What is a US OSAT?
OSAT stands for outsourced semiconductor assembly and test. An OSAT takes finished die from a foundry or a die bank and delivers packaged, tested parts. A US OSAT performs that work on US soil with a domestic engineering team. Heisler Semiconductor is a US OSAT in Halethorpe, Maryland, focused on prototype and low-to-mid-volume advanced-packaging programs.
Does Heisler accept low-volume and prototype orders?
Yes. Low volume is welcome here — first articles, DOE lots, engineering builds, and pilot runs are how most programs start, and prototype quantities get the same process discipline and per-build documentation as a production run. The ceiling is not low: automated assembly runs at 3,000 components per hour per system, on multiple systems, so the same line carries a program from one unit into production volume.
What assembly processes does Heisler run as an OSAT?
Die attach (eutectic, epoxy, silver sinter, fluxless), gold thermosonic ball and aluminum ultrasonic wedge wire bond, flip chip (C4, C2 copper pillar, Au-stud) with capillary or no-flow underfill, hermetic seam-weld and solder-seal packaging with fine and gross leak test, 3D heterogeneous integration, wafer-level processing, laser micromachining, and inspection and metrology including X-ray, 3D AOI, and SEM.
How does prototype-to-volume work at Heisler?
The prototype and the production run stay on the same line with the same engineering team. We build a test vehicle, run the DOE, prove the process window, then scale the proven process — so there is no re-qualification handoff to a separate volume supplier.
Is Heisler a foundry or a die manufacturer?
No. Heisler is not a foundry, not an IDM, and does not design or sell its own chips. We are a services provider: packaging, assembly, inspection, and test of die our customers supply.
Where is the OSAT work performed?
On US soil, at our facility in Halethorpe, Maryland, in the Baltimore area. Assembly, process development, and engineering are all performed domestically by one team.
Process More.
Bring us the small program.
Ten units on a substrate nobody else will touch, or a pilot build that has to become production without changing hands — send the process, geometry, and quantity, and we will tell you what a first engagement looks like.
Request a Capability Brief →/ US-soil assembly / prototype quantities / 3,000 cph per system / one engineering team