PCB FABRICATION

Calpak USA fabricates printed circuit boards from single-sided 1-layer designs up to complex 30-layer stack-ups. High layer count boards use vacuum lamination and sequential lamination processes to maintain precise layer-to-layer registration, typically holding alignment within 2 to 3 mils across the panel. Blind and buried vias, stacked microvias, and back-drilled vias are supported for high-density interconnect designs that require routing density beyond what surface layers alone can provide. Calpak USA's fabrication team at our Hawthorne, California facility works with your design team to optimize the stack-up for impedance targets, signal integrity, and thermal management. For layer counts above 20, Calpak USA recommends early engagement so we can review material selection, press cycles, and drill aspect ratios before Gerber files are finalized. All multi-layer fabrication is performed to IPC Class 2 or Class 3 standards as specified.

Calpak USA offers a comprehensive selection of surface finishes to match your assembly process and reliability requirements. Options include ENIG (electroless nickel immersion gold) for fine-pitch SMT and wire bonding applications, HASL (hot air solder leveling) in both leaded and lead-free formulations for cost-effective general-purpose boards, immersion silver for high-frequency RF designs requiring low contact resistance, immersion tin for press-fit connector applications, OSP (organic solderability preservative) for high-volume lead-free assembly, hard gold for edge connectors and high-wear contact surfaces, and soft bondable gold for wire bond pads. Calpak USA's engineering team at our Hawthorne, California facility can recommend the optimal finish based on your solder process, shelf-life requirements, number of reflow cycles, and end-use environment. Surface finish selection is confirmed during DFM review before fabrication begins.

Yes. Calpak USA fabricates single-layer and multi-layer flex circuits using polyimide (Kapton) and non-Kapton flexible substrates, as well as rigid-flex combinations that integrate rigid FR-4 sections with flexible polyimide interconnects in a single board. Rigid-flex designs reduce connector count, save weight, and improve reliability in applications that require dynamic bending or dense three-dimensional packaging. Calpak USA supports flex constructions with cover layers, stiffeners, adhesiveless laminates, and controlled impedance on flex layers. Minimum bend radius and cycle-life requirements are reviewed during DFM to ensure the design meets IPC-2223 guidelines for flex and rigid-flex circuits. Both prototype and production volumes are supported from our Hawthorne, California facility with IPC Class 2 and Class 3 compliance. Calpak USA recommends submitting a stack-up drawing and bend requirement specifications with your Gerber files for accurate quoting.

Calpak USA achieves minimum trace widths down to 2 mils (0.002 inches / 50 microns) and minimum air gaps of 3 mils (0.003 inches / 75 microns) for fine-line fabrication on inner and outer layers. Standard production designs typically use 4-mil trace and 4-mil space, which provides a good balance of manufacturing yield and routing density. For HDI designs requiring tighter geometries, Calpak USA supports laser-drilled microvias down to 4-mil diameter and sequential build-up layers. Annular ring minimums are 3 mils for inner layers and 4 mils for outer layers under standard tolerances, with tighter rings available for controlled-process builds. Our Hawthorne, California engineering team reviews trace and space requirements during DFM and may recommend adjustments to improve yield without compromising your routing density or impedance targets. All fine-line fabrication is verified with automated optical inspection.

Controlled impedance fabrication at Calpak USA begins with impedance modeling during the stack-up design phase, where dielectric thickness, trace width, copper weight, and material Dk values are calculated to achieve your target impedance within a specified tolerance, typically plus or minus 10 percent for single-ended and differential pairs. Calpak USA fabricates impedance test coupons on each production panel, and these coupons are measured using time-domain reflectometry equipment after fabrication. TDR sends a fast-rise signal pulse through the test coupon trace and measures the reflected signal to determine the characteristic impedance at every point along the conductor. Calpak USA provides TDR test reports with measured impedance values, target values, and pass/fail status for each coupon. Reports are included with shipment from our Hawthorne, California facility at no additional charge for controlled impedance orders. Failing panels are rejected before board singulation.

Calpak USA fabricates PCBs using a wide range of substrate materials beyond standard FR-4. High-performance options include high-Tg FR-4 (Tg 170C and above) for lead-free assembly and elevated operating temperatures, Rogers laminates (RO4003C, RO4350B, RO3003) for RF and microwave circuits requiring low dielectric loss, PTFE (Teflon) for millimeter-wave and high-frequency applications, polyimide for flex circuits and high-temperature environments, ceramic-filled hydrocarbon laminates for stable Dk across temperature and frequency, and metal-core substrates (aluminum and copper) for LED and power electronics thermal management. Calpak USA also supports mixed-dielectric constructions that combine FR-4 with Rogers or PTFE layers for cost-optimized RF boards. Material selection is reviewed during DFM at our Hawthorne, California facility, and Calpak USA maintains relationships with major laminate suppliers to ensure material availability and consistent lot-to-lot Dk performance.