Where to get PCB fab and assembly for blind vias and immersion silver

You can source blind‑via PCB fabrication with immersion‑silver (ImAg) finish and turnkey assembly from PCB vendors and EMS providers that explicitly publish laser‑microvia, sequential‑lamination, and ImAg (IPC‑4553) capability—use the checklist below to qualify them and avoid yield risk.

Short answer: sourcing blind vias with immersion silver

Look for fabs that state laser‑drilled microvias (L1–L2 and deeper), via‑fill and planarization for via‑in‑pad, and immersion‑silver finishing, then pair with an assembler experienced with ImAg solderability and storage. Ask for a microsection report and capability table before you commit.

What to verify in a fab for blind vias?

• Laser microvia limits: finished hole 75–100 µm, capture pad ≥ 225–300 µm, aspect ratio ≤ 1:1, stacked vs. staggered policy, and registration tolerance ≤ ±50 µm

• Sequential lamination: maximum lam cycles supported (e.g., two cycles for stacked L1–L2–L3), press‑fit warpage spec (≤ 0.7% typical), and coupon strategy

• Via‑in‑pad: resin‑ or copper‑filled and copper‑capped microvias with planarity ≤ 20–30 µm for BGAs ≤ 0.5 mm pitch

• Inner‑layer imaging: LDI or equivalent for 50–75 µm trace/space, and defined annular rings (≥ 50 µm on microvias)

• Reliability data: IST or HATS on stacked microvias across six reflows, and cross‑sections showing no interfacial separation

Immersion silver finish: assembly and handling

Immersion silver per IPC‑4553 typically deposits ~0.12–0.40 µm Ag over copper. It wets readily with SnAgCu and supports multiple reflows, but silver is susceptible to sulfur‑driven tarnish.

• Storage: vacuum‑seal with desiccant and sulfur‑free paper; target <30°C and <60% RH; minimize open time before assembly

• Reflow: nitrogen can reduce oxidation; use no‑clean fluxes compatible with ImAg; avoid aggressive chemistries that attack silver

• Stencil/paste: 100 µm (4 mil) laser‑cut stainless stencils work well for 0.5 mm BGAs with Type‑4 paste; tune area ratio ≥ 0.5 on fine apertures

• Cleanliness: insist on low ionic contamination (tested per IPC‑TM‑650 2.3.25) to prevent creep corrosion on silver

Stackup, design rules, and DFM data you should send

Provide a complete data pack so the fab/EMS can confirm yield before quoting.

• Files: ODB++ or Gerber X2, drill map labeling blind/buried spans, netlist, pick‑and‑place, paste layers, BOM with MPNs

• Stackup: core/prepreg list (e.g., FR‑4 with 7628/2116 prepregs), copper weights, target lamination cycles, which layers get blind vias

• Impedance: targets and tolerances (e.g., 90 Ω or 100 Ω differential, 50 Ω single‑ended), preferred dielectric constants and loss tangents if RF

• Microvia usage: BGA pitch and via‑in‑pad locations; keepout rings around microvias (≥ 200 µm) to avoid resin starvation

• Solder mask: expansion 50–75 µm; NSMD pads for fine‑pitch BGAs on ImAg are common for better filleting

What HyperPCB offers for quality and compliance

HyperPCB operates an ISO 9001:2015 certified quality management system (certificate CN‑2023‑Q1156, SGS, valid to June 2027). We return quotes within 24 hours and DFM feedback within 1 business day. Boards can be built and inspected to IPC Class 2 or IPC Class 3 acceptance criteria. RoHS and REACH compliance is supported for hazardous substance control. Our partner factory AEGIS maintains ISO 9001:2015, ISO 14001:2015 and ISO 45001:2018 management systems, plus ISO 13485:2016 and IATF 16949. AEGIS also manufactures high‑frequency laminates and supplies RF PCB fabricators in China, including publicly listed PCB companies.

How do I shortlist vendors quickly?

Start with published microvia and ImAg capability tables, ask for recent microsections of stacked microvias, require IPC Class 2/3 acceptance, and confirm assembly experience on ImAg with your BGA pitch and paste type. Then run a small pilot to validate solder wetting and X‑ray fillets before ramp.