# Electronic Fabrication & PCB Assembly Standards Guide
> Master electronic fabrication processes including PCB baking, lead tinning, coil winding, CQFP preparation, and soldering standards for high-reliability.

Tags: pcb-assembly, soldering-standards, electronic-fabrication, circuit-board-inspection, coil-winding, surface-mount-technology, industrial-manufacturing
## Electronic Fabrication Processes
*   Technical standards for assembly, wiring, and inspection.
*   Focus on Process Assurance Division requirements.

## Pre-Fabrication: Inspection & Baking
*   **Visual Inspection:** Check for laminate, conductor, and plating defects.
*   **PCB Baking:** General baking at 85°C; Reflow preparation at 120°C for 3 hours.

## Lead Preparation & Turret Swaging
*   **Lead Tinning:** Dross-free solder pot at 240-280°C; 2-3 seconds dwell time.
*   **Turret Swaging:** Punch-to-anvil distance must match PCB thickness to prevent board damage.

## Coil Winding Procedures
*   **Single Winding:** (Length × Turns) + 10% Overhead + 30cm.
*   **Bifilar Winding:** Fold wire in half before starting; 15cm termination leads.
*   **Testing:** All coils must pass dry probe testing before assembly.

## CQFP Component Preparation
*   Corrosion inspection under magnification.
*   Lead forming jig height set to component thickness + 25 mils.
*   Vertical removal from jigs to maintain lead alignment.

## Specialized Wiring: PRT & 1553 Cables
*   Manual lead cleaning at 45° angle with a surgical knife.
*   1553 Shield Isolation: Outer jacket stripping (10mm) and window creation (60mm).

## Connector De-Golding Process
*   **Objective:** Remove gold plating to prevent brittle solder joints.
*   **Method:** Double-dip at 250°C for 2-3 seconds.

## Component Mounting Standards
*   **Parallelity:** Components must remain parallel to each other and flush to the PWB.
*   **Lead Protrusion:** 1-1.5mm standard for ICs and Transistors.
*   **Stress Relief:** Bend radius should be 3D to 6D.

## Soldering Process Control
*   **Temperature:** Preferred range 240°C - 280°C; absolute maximum 300°C.
*   **Technique:** Apply solder to the joint, not the iron. Never move the iron while the joint is cooling.

## Thermal Interfaces & Special Mounting
*   **Thermal Materials:** Use Chotherm 1671/974 for axial and DIP components.
*   **Turret Spacing:** Mount components 1.2 to 1.5mm from the base.

## Capacitor Soldering & Stacking
*   **Preheating:** Ceramic chips at 100°C for 10 minutes.
*   **Stacking:** Max 4 capacitors for CWR 06 stacks; bonded with Epotek H74 cured at 150°C.
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