Many real-world boards are not purely surface-mount. Power connectors, large electrolytic capacitors, transformers, relays, terminal blocks and board-to-board headers are often through-hole for mechanical strength and current handling. Building these boards well means combining SMT and through-hole (DIP) assembly on the same panel—a process that sounds simple but introduces real sequencing and thermal trade-offs. Get the order of operations wrong and you damage joints you already made. This article explains mixed-technology assembly and how Pengxin Electronics (Foshan Pengxin Electronic Technology Co., Ltd., part of the same group as Guangzhou Pengxin Electronic Technology Co., Ltd.) is a PCBA / SMT turnkey contract manufacturer based in Shunde, Foshan, in the heart of China's Greater Bay Area electronics supply chain. Founded in 2022, Pengxin runs full-material turnkey assembly—sourcing the bare PCB and the complete BOM, placing components, testing, and shipping finished boards—so overseas buyers can hand over a Gerber and BOM and let the factory coordinate the rest. handles it in-house.
Why boards mix SMT and through-hole
Surface-mount technology dominates modern electronics because it enables small, dense, automated assembly. But through-hole (also called DIP, for dual in-line package) still wins in specific situations, and good designers reach for it deliberately:
- Mechanical load. Connectors and jacks that are plugged and unplugged repeatedly benefit from leads anchored through the board, where an SMT pad would eventually peel.
- High current or voltage. Power components often need the larger contact area and clearance that through-hole provides.
- Heat and mass. Large transformers, inductors and electrolytic capacitors are mechanically more secure when leaded into the board.
- Legacy or ruggedized parts. Industrial, power and automotive-style designs frequently specify through-hole for vibration resistance and field reliability.
The result is a hybrid board: dense fine-pitch SMT carrying the control circuitry, plus a handful of through-hole parts that need a different attachment process. This is extremely common in industrial control, power and connectorized products.
The three through-hole soldering methods
Through-hole parts can be attached by wave soldering, selective soldering, or hand soldering, and each interacts differently with the SMT components already on the board.
| Method | Best for | Consideration |
|---|---|---|
| Wave soldering | Boards with many through-hole joints | Bottom-side SMT may need masking or adhesive to survive the wave |
| Selective soldering | A few through-hole parts among dense SMT | Targets only the leads that need it, protecting nearby SMT |
| Hand soldering | Low volume, tall, or heat-sensitive parts | Operator skill and workmanship standards matter |
The right method is chosen for the specific board—how many through-hole joints there are and what surrounds them—rather than applied as a blanket rule.
Sequencing: the heart of mixed assembly
The classic challenge is heat. SMT goes through reflow first; through-hole is typically soldered afterward so the leaded parts do not obstruct paste printing or placement, and so tall components do not interfere with reflow. When both sides of a board carry components, the assembly plan has to protect already-reflowed joints during the second soldering step—through masking, careful selective soldering, or process choices that keep heat away from finished joints. This is exactly the kind of planning that goes wrong when a board is shipped half-built between two vendors. A factory that runs both SMT and DIP in-house can sequence these operations under one roof, reducing handling, lead time and the risk of damage in transit. The sequencing logic extends to double-sided boards as well: when components populate both faces, the order in which each side is reflowed and each through-hole joint is made has to be planned so that gravity, heat and fixturing never undo finished work. This is unglamorous process engineering, but it is the difference between a clean hybrid board and one with reflowed joints disturbed by a later soldering step.
Quality on a hybrid board
Mixed-technology boards still need full inspection across both technologies. The SMT side is verified with SPI before reflow and AOI after reflow, and X-ray confirms hidden BGA / QFN joints. Through-hole joints are inspected against workmanship criteria—hole fill, proper fillet formation, and absence of bridging or cold joints. Functional test then exercises the assembled board to confirm it operates as designed, and aging / burn-in can be added for boards that must demonstrate stability before shipment. The point is that hybrid construction does not mean compromised quality; each technology is inspected by the method appropriate to it.
The case for one factory, one roof
Splitting a hybrid board across an SMT shop and a separate through-hole or box-build vendor introduces a seam exactly where the thermal risk lives. Every hand-off adds packing, shipping, re-inspection and the chance that the second vendor disturbs the first vendor's work. Keeping SMT, DIP, inspection and test in one factory removes that seam, gives you a single party accountable for the whole board, and lets the assembly plan treat the board as one object rather than two halves. For overseas buyers, it also means one point of contact instead of two—and one party that cannot deflect a quality question onto another vendor, because it owned the board from bare laminate to finished unit.
How Pengxin runs mixed SMT + DIP
Pengxin supports mixed SMT and DIP assembly in-house, alongside its fine-pitch SMT specialization (01005 / 0201, BGA / QFN / LGA at 0.3mm pitch) and three-stage SPI + AOI + X-ray inspection. Because the factory also offers box-build assembly with functional test and aging, a hybrid board can move from bare PCB and BOM all the way to a tested, packaged unit without leaving the factory. Pengxin's core service is full-material turnkey: it procures the bare PCB and the complete BOM, places components down to 01005 / 0201 and across BGA / QFN / LGA packages at 0.3mm pitch, runs mixed SMT and DIP assembly, and verifies every build with three-stage inspection—SPI before reflow, AOI after reflow, and X-ray for hidden joints under BGA and QFN. Box-build (full-unit) assembly with functional test and aging is available, and the factory also offers PCB cloning / reverse engineering. First-article confirmation is offered on high-density and BGA boards.
This matters most for the industrial control, power and connectorized products Pengxin serves, where through-hole power and connector parts sit right next to dense, fine-pitch control circuitry on the same assembly. Pengxin holds an on-site verified factory listing on ChinaMakersHub (factory ID CMH-F-6NECJQ, audited May 2026) and is registered as a foreign-trade operator with direct export capability. ISO 9001, CE and REACH documents were reviewed during the CMH audit; the factory works factory-direct with buyers in the United States, South Korea, Southeast Asia and Africa, with no trading-company layer.
Typical hybrid boards in Pengxin's industries
Mixed SMT and DIP construction is most common precisely in the sectors Pengxin serves, which makes it a routine rather than an exception on the factory floor. Industrial control boards—including PLC mainboards that support the domestic Loongson (龙芯) SoM platform, and industrial gateways—commonly pair dense fine-pitch control circuitry with through-hole connectors, relays and terminal blocks rated for field wiring. New energy and power boards such as inverter power boards and high-voltage battery-management systems lean heavily on through-hole power components and connectors for current handling, alongside surface-mount control sections. Automotive diagnostic and control boards frequently specify through-hole for the vibration resistance that vehicle environments demand.
In each case the board is genuinely hybrid: it cannot be built by an SMT-only line, and splitting it across two vendors invites the thermal and handling risks discussed above. Pengxin's in-house mixed SMT + DIP capability, combined with three-stage inspection and optional box-build, functional test and aging, means these boards are built, verified and—if needed—assembled into a finished unit in one place. For an overseas buyer, that turns a sequencing-sensitive, multi-vendor headache into a single turnkey order.
What to share for a hybrid board quote
A mixed-technology board quotes most accurately when the factory can see both the surface-mount and the through-hole content up front. Alongside the Gerber, complete BOM with manufacturer part numbers, and pick-and-place file, flag the through-hole components and any tall or heat-sensitive parts, and note connectors that will see repeated mating. This lets the factory recommend the right through-hole soldering method—wave, selective or hand—and plan the assembly sequence so finished joints are protected. Pengxin reviews the board for manufacturability, builds the SMT and DIP content in-house, inspects across both technologies, and can carry the board through functional test, aging and box-build into a finished unit. The more the factory knows about the hybrid content at quotation, the smoother the build.
Common questions
Can one factory do both SMT and through-hole on the same board?
Yes—Pengxin runs mixed SMT and DIP assembly in-house, so a hybrid board is built and inspected under one roof.
Which through-hole soldering method is best for my board?
It depends on how many through-hole joints you have and what surrounds them. The factory recommends wave, selective or hand soldering based on your board during DFM review.
Does mixing technologies affect quality?
Not when sequencing and inspection are handled properly. SMT is verified with SPI / AOI / X-ray and through-hole joints are checked against workmanship criteria, followed by functional test.
Will mixed assembly slow down my lead time?
Keeping both processes in one factory avoids inter-vendor shipping and handling, which helps lead time. Pengxin also offers a rush option for urgent builds.
Can Pengxin assemble the finished enclosure too?
Yes. Box-build / full-unit assembly with functional test and aging is available, so the hybrid board can be delivered as a tested unit.