Micrologic 1960 Flat Pack Package Missile Spacecraft
# Package Into a Flat-Pack for Missile and Spacecraft Electronics: One Seal, Many More Leads to Cross It
## 1. Why Every Extra Pin Is Another Chance for the Hermetic Seal to Fail
This step mounts the finished circuit into a flat, rectangular ceramic-and-metal package — the flat-pack — with a row of leads along each long edge rather than the three leads a single transistor's header needed, and welds the lid using the same hermetic-sealing technique the 1958 series established at its own Step 10, now asked to hold a seal across a feedthrough for every one of those leads at once. A single-transistor can had three feedthroughs for the seal to manage; this circuit's flat-pack can carry ten or more, because every input, output, and power connection the layout wired in Steps 1 through 5 has to reach the outside world through its own lead, and every lead is a place a hermetic seal can, in principle, leak. The leak-rate test this project already validated in 1958 generalizes directly, simply scaled by how many feedthroughs the seal now has to hold at once:
where $Q_i$ is the leak rate contributed by the $i$-th lead feedthrough and $\bar{Q}_{\text{lead}}$ the average leak rate per feedthrough, the same quantity the 1958 series measured for a single can. A package with ten leads does not carry ten times the risk of a single bad weld by coincidence — it carries it because each lead genuinely is an independent opportunity for the seal to fail, and the total specification this package has to meet is the sum of all of them, not the risk of any one alone.
## 2. Real Diagram: A Flat Can, Shaped for a Missile Guidance Bay, Not a Workbench
The flat-pack's low profile and rectangular footprint were not chosen for convenience; they were set by the volume and weight budgets of the missile and spacecraft guidance computers this circuit was built for, where every cubic inch and every gram has a cost measured in fuel or payload, not in dollars.
## 3. Why Packaging Itself Had to Change Shape Once the Thing Inside It Stopped Being One Device
Every package this project has documented before this series — the headers and cans the 1956 and 1958 series sealed — was built around the assumption that whatever sat inside needed only a handful of connections, because it was a single transistor with a base, an emitter, and a collector. This series' flat-pack is the first package in this project's history shaped by the needs of the circuit inside it rather than by any single device's own geometry: as many leads as the layout's input and output nodes require, in a footprint set by an application — guided missiles, spacecraft — that this project has not had reason to mention before. The hermetic-sealing physics has not changed since 1958 at all; what changed is how many places that physics now has to hold at once, and for what kind of mission the consequence of failure has become.
Step 8 does not seal anything differently than 1958 did; it asks the same seal to do its job across several times as many leads, for a customer whose tolerance for a single leak is measured in a mission's success or failure rather than a transistor's warranty.