| 1 |
Select the Appropriate PCB Material |
Laminate thermal performance |
Standard FR-4 materials commonly have a glass-transition temperature
(Tg) of approximately 130–170°C.
High-Tg grades are generally around 170°C or higher.
|
Use standard FR-4 for ordinary commercial products. Consider high-Tg or
low-loss materials for high-temperature, multilayer, or high-speed applications.
|
Delamination, excessive warpage, and reduced reliability during repeated thermal cycling |
| 2 |
Confirm the Layer Stackup |
Number of layers and impedance requirements |
Common rigid boards use 2–12 layers. Controlled-impedance
designs often specify 50 Ω single-ended or
90–100 Ω differential routing, depending on the interface.
|
Request the proposed stackup, dielectric thicknesses, copper weights, and
impedance calculations before fabrication.
|
Signal loss, crosstalk, layer mismatch, and unexpected fabrication cost |
| 3 |
Compare Copper Weight and Current Capacity |
Outer and inner layer copper thickness |
1 oz copper ≈ 35 µm nominal thickness;
2 oz copper ≈ 70 µm. Higher copper weight improves
current capacity but may require wider spacing and modified etching rules.
|
Specify copper weight separately for outer and inner layers, and verify
trace width using the required current and allowable temperature rise.
|
Overheating, voltage drop, insufficient clearance, and difficult fine-line fabrication |
| 4 |
Choose the Surface Finish Carefully |
Solderability, storage life, and contact performance |
Lead-free HASL is economical and suitable for many general assemblies.
ENIG provides a flat surface for fine-pitch parts. OSP is a thin organic
coating suitable for controlled handling and shorter storage periods.
|
Use a flat finish for fine-pitch or bottom-terminated components. Match the
finish to storage time, contact requirements, and the number of reflow cycles.
|
Oxidation, uneven solder joints, poor contact reliability, and assembly defects |
| 5 |
Check Component Availability and Lifecycle |
Availability, substitution, and lifecycle status |
Lead times can change from days to several months depending on package,
semiconductor category, demand, and order quantity. A single-source part
creates a higher continuity risk than an approved multi-source alternative.
|
Approve alternative part numbers, define electrical and mechanical equivalence,
and obtain date-code, moisture-sensitivity, and traceability requirements.
|
Production stoppages, unauthorized substitutions, counterfeit parts, and redesign delays |
| 6 |
Match Package Pitch to Assembly Capability |
Component package size and placement accuracy |
Common fine-pitch packages include approximately 0.5 mm QFP
and 0.4–0.8 mm BGA. Smaller pitches demand tighter
solder-mask registration, stencil control, and inspection capability.
|
Ask for minimum component pitch, placement accuracy, pad-design rules, and
validated land-pattern data before selecting a package.
|
Bridging, opens, pad misregistration, solder shorts, and difficult rework |
| 7 |
Select the Right Assembly Technology |
SMT, through-hole, or mixed technology |
SMT supports high component density and automated placement. Through-hole
provides strong mechanical retention for connectors and high-stress parts.
Mixed-technology assemblies combine both methods on one board.
|
Use SMT for compact electronic functions, through-hole for mechanically
stressed components, and mixed technology when electrical and mechanical
needs differ.
|
Low assembly efficiency, weak mechanical joints, increased manual labor, and higher cost |
| 8 |
Define the Soldering Process |
Reflow, wave, selective, or hand soldering |
Lead-free SAC solder alloys have a liquidus temperature of approximately
217°C; typical lead-free reflow peak temperatures
are often about 235–250°C, subject to the component
and paste supplier profile.
|
Approve the thermal profile, maximum component temperature, number of reflow
cycles, solder paste type, and cleaning requirements before mass production.
|
Cold joints, component damage, voiding, tombstoning, and insufficient solder wetting |
| 9 |
Build Inspection into the Process |
Inspection coverage and test strategy |
AOI detects many visible placement and soldering defects. X-ray inspection
is useful for hidden joints such as BGAs and bottom-terminated components.
ICT and functional testing verify electrical behavior at different stages.
|
Define inspection points, sampling or 100% inspection requirements, test
coverage, defect classification, and acceptance criteria before production.
|
Escaped defects, hidden solder faults, intermittent failures, and costly field returns |
| 10 |
Verify Compliance and International Logistics |
Regulatory documentation and shipment control |
Typical compliance documentation may include RoHS declarations, REACH-related
material information, conflict-minerals statements, material declarations,
certificates of conformity, and lot traceability records.
|
Confirm the destination-market requirements, packaging standards, moisture
protection, labeling, export documents, Incoterms, and agreed quality records.
|
Customs delays, restricted-material violations, moisture damage, and incomplete traceability |
