Component placement on the wave side decides whether joints solder well: through-hole components go through wave soldering, and some SMDs can too, but some packages must be reflowed (for example, in one semiconductor maker’s note, the type with an exposed thermal pad on the bottom); check the component maker’s specification. Small two-terminal parts should be perpendicular to the direction of travel so both ends touch the solder at the same time; multi-lead ICs are placed along the direction of the wave, with a solder thief pad after the last lead of each row; small parts should not hide behind large parts, and SMDs should not be too close to through-hole leads. A wave solder pallet is needed just when the board has bottom-side parts that must not get solder, warps at lead-free temperatures, or has an irregular outline that cannot ride the conveyor; the pallet openings should be as large as possible. This article is about how to place components on the wave side and when to use a wave solder pallet; wave machine parameter settings, selection of selective soldering machines and choice of flux are out of scope. It is divided into 5 stages:
Stage ① | First sort which parts can go over the wave: through-hole, some SMDs, and packages that must be reflowed.
Stage ② | Orientation: two-terminal parts, multi-lead ICs and large through-hole connectors each have rules.
Stage ③ | Spacing, shadowing and pads: do not be blocked by large parts, do not sit too close to through-hole leads, pads not too large.
Stage ④ | When to use a pallet: bottom-side parts need protecting, the board warps, the outline is irregular.
Stage ⑤ | Pallet design and validation: openings as large as possible, board lying flat, watch for heat absorption and flux dead spots.
Each stage below covers: how to do it, what public sources say, and, where there is a match, what Jiahon can help with; sources, exceptions and this article’s own summaries are in the “Notes” at the end. This is the general case and still depends on the individual case.
Figure 1: The five stages of component placement for wave soldering (schematic). ① Can it go over the wave — through-hole: wave soldering; some SMDs: placed by the rules; some packages: must be reflowed, check the specification. Result: a list of wave-side components. ② Orientation — two-terminal parts: perpendicular to travel; multi-lead ICs: along the wave; large connectors: perpendicular to the wave. Result: a drawing with orientations marked. ③ Spacing and pads — not shadowed: small parts not behind large ones; distance from through-hole leads: not too close; solder thief pads: at the end of each row. Result: pads and spacing. ④ Pallet or not — bottom-side parts: cover them; board warps: support it; irregular outline: cannot ride the conveyor. Result: a decision on whether to use a pallet. ⑤ Pallet and validation — openings: as large as possible; heat absorption: do not let the temperature drop; flux: no dead spots. Result: validated soldering conditions.
Stage ①: First sort which parts can go over the wave
How to do it:
Through-hole components: usually go through wave soldering (source 1).
Some SMDs: some SMDs can also go over the wave, but placement has to follow rules (source 1).
Some packages must be reflowed: a semiconductor maker’s application note says that among its own two packages, the type with an exposed thermal pad on the bottom must be reflowed; it recommends reflow for both packages, and wave soldering just when reflow equipment is not available or not wanted (source 3). Whether other components can go over the wave depends on each component maker’s specification (this article’s own summary).
Parts that are too tall: if parts on the wave side are too tall, that side may not be able to go through wave soldering (source 1).
Ask about the direction of travel first: before layout, the designer needs to know which direction the board travels through the wave machine (source 1).
Make a list: list every type of component on the wave side, marking whether it can go over the wave and whether it needs adhesive (this article’s own summary).
What public sources say: a blog article by an electronics manufacturing services company (published 2023, updated 2025) says: through-hole parts usually go through wave soldering, and some SMDs can too; the designer needs to know the direction of travel before layout; parts that are too tall can stop that side from going over the wave. A semiconductor maker’s application note on wave soldering design (March 2023) says: among its own two packages, the type with an exposed thermal pad on the bottom must be reflowed with infrared or hot air; reflow is recommended for both packages, and wave soldering is used just when reflow equipment is not available or not wanted (notes table 1).
What Jiahon Can Help With:
- Solder bars: the product page says the solder bars are mainly used in the wave soldering process of electronics assembly plants and the hot air solder leveling process of PCB makers.
Stage ②: Orientation
How to do it:
Small two-terminal parts: the body perpendicular to the direction of travel, so both ends touch the solder at the same time (source 1).
Multi-lead ICs: placed along the direction of the wave, so the trailing leads are not blocked by the leading ones (source 1); the application note, for its own two packages, says: the leads should be perpendicular to the board’s direction of travel (source 3).
The last lead of each row: add a large pad (solder thief pad) at the trailing end of the fine-pitch row to draw off excess solder and avoid shorts (source 3).
Large through-hole connectors: place them perpendicular to the wave; when the leads line up in a row along the wave, the trailing leads are more likely to be missed (source 1).
Draw the orientation on the drawing: mark the direction of travel with an arrow on the assembly drawing, so layout and process look at the same drawing (this article’s own summary).
Figure 2: Placement orientation on the wave side (schematic, based on sources 1 and 3). Arrow: the board’s direction of travel through the wave machine. Two-terminal parts: perpendicular to the direction of travel. Multi-lead IC: placed along the direction of the wave; gold: the solder thief pad at the end of each row. Large through-hole connector: the row of leads perpendicular to the wave. Red: a small part hiding behind a large part will be shadowed. Four placement principles: know the direction of travel first; both ends of two-terminal parts soldered at once; a solder thief pad at the end of each row of a multi-lead IC; small parts not behind large ones.
What public sources say: the EMS company’s article mentioned above says: multi-lead SMDs (for example ICs) can go over the wave, but should be placed along the direction of the wave so the trailing leads are not blocked; small discrete parts should be perpendicular to the direction of travel so both leads solder at once; large through-hole connectors should be perpendicular to the wave, because when the leads line up along the wave, the trailing leads are easily missed. The application note mentioned above says: when its two packages pass through wave soldering, the leads must be perpendicular to the board’s direction of travel; large pads are placed at the trailing end of each row of fine-pitch leads as solder thieves, and the size, position and shape of the solder thief may need adjusting for the wave soldering equipment (notes table 1).
Stage ③: Spacing, shadowing and pads
How to do it:
Do not get shadowed: do not place small SMDs behind large parts (along the direction of the wave), so they are not shadowed (source 1).
Not too close to through-hole leads: SMDs on the back side too close to through-hole leads will block the wave and solder poorly (source 1).
Pads not too large: pads that are too large short easily; follow the IPC pad guidelines (source 1).
Pad spacing as wide as possible: as long as joints can still form, the wider the spacing between pads, the less likely shorts are (source 3).
Equipment makes a difference too: the application note says that with newer wave soldering equipment that has anti-bridging features, its two packages can be soldered well; for older or simpler equipment, it recommends special pad design; the solder thief is a practice it describes as “proven effective” (source 3).
What public sources say: the EMS company’s article mentioned above says: large parts shadow small SMDs behind them; back-side SMDs too close to through-hole leads block the wave; pads that are too large cause shorts, and it suggests following the IPC pad guidelines. The application note mentioned above says: pad spacing should be as wide as possible to avoid shorts, while still allowing good joints around each lead; with newer equipment that has anti-bridging features, its two packages can be wave soldered successfully; for older or simpler wave soldering equipment, special PCB pad design is recommended; the solder thief practice has been proven effective (notes table 1).
Stage ④: When to use a pallet
How to do it:
Bottom-side parts that must not get solder: use a pallet to cover the SMDs on the wave side, letting just the through-hole leads touch the solder (source 2).
The board warps: lead-free soldering temperatures are higher and boards warp easily; a pallet can support the board (source 2).
Irregular outline: boards with odd shapes that the conveyor cannot hold can ride on a pallet (source 2).
The ideal choice for mixed technology: a senior process engineer wrote in a trade magazine that for mixed-technology boards with both through-hole and SMD parts, selective soldering is the ideal choice; when equipment and throughput are not enough, covering the SMDs with a pallet and then wave soldering is a workable alternative (source 2).
When you may not need one: if the wave side has just through-hole parts or parts that can go over the wave, the board does not warp, and the outline is regular enough to ride the conveyor directly, a pallet is not necessarily needed (this article’s own summary, inferred from the situations source 2 lists as needing one).
What public sources say: an article by a senior process engineer in a trade magazine (May 2006) says: for mixed-technology boards, selective soldering is the ideal choice, but not every company has the equipment or the throughput; covering the SMDs with a pallet and wave soldering gives high throughput and short cycle times; lead-free soldering temperatures are high and boards warp, and a pallet can support the board; boards with odd shapes are hard to carry on chains or conveyors, and a pallet solves this; a pallet can also protect parts on the wave side (notes table 2).
What Jiahon Can Help With:
- When you need a custom fixture such as a wave solder pallet, Jiahon’s “Process and Fixture Design” page says “What standard products cannot solve, leave to us to assess, design and make.” Customers are asked to send photos or drawings, and the engineering department replies whether it can be made and how.
Stage ⑤: Pallet design and validation
How to do it:
Openings as large as possible: the larger the openings in the pallet, the more freely the solder flows; the source says this can eliminate defects such as shorts and solder balls, and also helps hole fill of through-holes (source 2).
Leave space front and back: leave space in front of and behind through-hole components so the solder can flow (source 2).
Board lying flat: the board has to lie flat in the pallet (source 2).
Watch for heat absorption: if the temperature drops before entering the wave, the pallet absorbs heat and the process goes out of control (source 2).
Watch for flux dead spots: with a poorly designed pallet, there are places the flux spray cannot reach (source 2).
The wave must be high enough: with a pallet, the wave height goes up to at most 0.5 inch (about 12.7 mm) (source 2).
Durability: a good pallet can last more than 3,000 soldering cycles (source 2).
Validation: after the first batch goes through with the pallet, look at through-hole fill, shorts, solder balls and flux residue, then decide whether to change the openings (this article’s own summary).
Figure 3: Cross-section of a wave solder pallet: pockets cover the bottom-side parts, and the openings let the wave touch just the through-hole leads (schematic, based on source 2). Dark gray = pallet; dark blue = bottom-side parts; light green = circuit board. Five points of pallet design: openings as large as possible; space in front of and behind through-hole parts; board lying flat; do not let the temperature drop, the pallet absorbs heat; no flux dead spots.
What public sources say: the trade magazine article mentioned above says: leave space in front of and behind through-hole parts so the solder can flow; pallet openings should be as large as possible, which can eliminate defects such as shorts and solder balls and help through-hole fill; the board should lie flat in the pallet; pallet material should be dimensionally stable, resistant to thermal shock, still flat after many uses, resistant to flux and cleaning agents, and non-absorbent, and a good pallet can last more than 3,000 cycles; poor pallet design leaves places the flux cannot reach; when the temperature drops before the wave, the pallet absorbs heat; with a pallet, the wave height goes up to at most 0.5 inch, and some pallets are as thick as 15 mm (notes table 2).
Notes: sources and exceptions
The following is for readers who need to check; skipping it does not affect the approach above. Where your product specifications, the component makers’ data, or the recommendations of your wave soldering equipment and pallet makers differ from this article, follow them.
Where each stage comes from
| Source | Where it is used, and the source |
|---|---|
| Source 1 | Stages ①, ②, ③: which parts can go over the wave, direction of travel, orientation of two-terminal parts and ICs, large connectors, shadowing, closeness to through-hole leads, pads too large; a blog article by an electronics manufacturing services company (vendor material, published October 2023, updated November 2025; dates taken from the page metadata) |
| Source 2 | Stages ④, ⑤: when to use a pallet, lead-free warpage, irregular outlines, openings and space, heat absorption, flux dead spots, wave height, durability; a trade magazine article by a senior process engineer (May 2006; the page does not explain the nature of the author’s company) |
| Source 3 | Stages ①, ②, ③: packages to be reflowed, leads perpendicular to travel, solder thief pads, pad spacing, equipment differences; a semiconductor maker’s application note on wave soldering design (vendor material, March 2023, see the cover and revision table; it covers just its own two packages) |
| Jiahon data | “What Jiahon Can Help With”; the Process and Fixture Design page |
Table 1 | Components, orientation and pads
| Item | What public sources say |
|---|---|
| Can go over the wave | Through-hole parts usually go through wave soldering, and some SMDs can too (source 1) |
| Must be reflowed | The type with an exposed thermal pad on the bottom, in that note; reflow is recommended for both of its packages, with wave soldering as the fallback (source 3) |
| Parts that are too tall | May stop that side from going over the wave (source 1) |
| Two-terminal parts | Perpendicular to the direction of travel, both ends soldered at once (source 1) |
| Multi-lead ICs | Along the direction of the wave (source 1); for the note’s two packages: leads perpendicular to the direction of travel (source 3) |
| Solder thief pads | Large pads at the trailing end of each row of fine-pitch leads; size and position adjusted for the equipment (source 3) |
| Large through-hole connectors | Perpendicular to the wave; when the leads line up along the wave, the trailing leads are easily missed (source 1) |
| Shadowing | Small parts not behind large parts; SMDs not too close to through-hole leads (source 1) |
| Pads | Too large shorts easily; follow IPC guidelines (source 1); spacing as wide as possible (source 3) |
Sources: see each row.
Table 2 | Pallets
| Item | What public sources say |
|---|---|
| Mixed technology | For boards with both through-hole and SMD parts, selective soldering is preferable; covering the SMDs with a pallet and wave soldering is a workable alternative (source 2) |
| When to use one | Protect wave-side parts, boards warping at lead-free temperatures, irregular outlines (source 2) |
| Openings | As large as possible; can eliminate shorts and solder balls and help hole fill (source 2) |
| Space | Space in front of and behind through-hole parts so the solder can flow (source 2) |
| Material | Dimensionally stable, resistant to thermal shock, still flat after many uses, chemical resistant, non-absorbent (source 2) |
| Durability | A good pallet can last more than 3,000 cycles (source 2) |
| Process | Wave height up to at most 0.5 inch; some pallets as thick as 15 mm; absorbs heat when the temperature drops; poor design leaves places the flux cannot reach (source 2) |
Sources: see each row.
Exceptions and limits
What was seen and what was not: this article read 3 public sources (an EMS company’s blog, a senior process engineer’s trade magazine article and a semiconductor maker’s application note), plus Jiahon’s Process and Fixture Design page. No full standard text on wave soldering component placement was read; the IPC pad guidelines mentioned in the text were not read by this article.
Positions and dates of the sources: source 1 is an EMS company, and its dates (published October 2023, updated November 2025) were taken from the page metadata and cannot be seen in the page text; the author of source 2 is a senior process engineer at a company, and the page does not explain the nature of the company; source 3 is a company that sells components, dated March 2023 (cover and revision table), and its content covers just its own two packages.
How orientation is written: source 1 says multi-lead ICs go “along the direction of the wave”; source 3, for its own two packages alone, says “leads perpendicular to the direction of travel”. Whether the two wordings mean the same thing is not explained by the sources, and this article does not infer it; please follow the component maker’s recommendation; the way Figure 2 is drawn is this article’s own summary. The recommendation for large through-hole connectors (perpendicular to the wave) is a different situation; do not mix them up.
Figures: the pad widths and spacings in source 3 apply just to its own packages and are not quoted here; the conversion of the 0.5-inch wave height was calculated by this article.
This article’s own summary: the list and “check the specification” in Stage ①, drawing the orientation on the drawing in Stage ② (Figures 1 to 3), when you may not need a pallet in Stage ④, and the validation and metric conversion in Stage ⑤ are this article’s own summary; the other sentences can be matched to statements in the sources or on Jiahon’s page.
Scope: this article discusses just component placement on the wave side and wave solder pallets; wave machine parameters, selection of selective soldering machines and flux are out of scope.
Jiahon’s page: “What Jiahon Can Help With” quotes just sentences from pages already published on the site.
This article is a summary of the general case, not a restatement of standard clauses, and not an endorsement of any EMS company, equipment supplier or component maker, nor an assurance for your products and processes. Please follow your product specifications, the component makers’ data, the recommendations of your equipment and pallet makers, and your own validation; this is the general case and still depends on the individual case.