3D Solder Paste Inspection
Measure the printed paste while the pads are still visible. Define deposit measurements, pad-family limits and the response to print variation before placement and reflow.
Check the paste deposit before it becomes a joint.
Three-dimensional solder paste inspection, or 3D SPI, measures exposed solder-paste deposits after printing and before component placement. Its measurement categories include deposit volume, height and area, with additional shape-related checks depending on the system. [S23]
For a GlobalWellPCB assembly, define SPI as a print-process checkpoint rather than a finished-joint test. Identify the critical pad families, the measurement reference and the action to take when a deposit falls outside the agreed process limits.
Review more than a single percentage.
The following are measurement and review topics for a project-specific SPI plan. There is no universal acceptance band that fits every aperture, package and printing process.
Scroll the table horizontally to see all columns.
| Review area | What to evaluate | What to agree |
|---|---|---|
| Deposit volume | The measured paste quantity over the defined inspection region. [S23] | State the reference volume and permitted limits for the pad family. |
| Deposit height | The vertical profile or height statistic reported by the selected system. [S23] | Define the reference plane and evaluated metric rather than just saying “height”. |
| Deposit area | The footprint of the deposit within the defined measurement region. [S23] | Review it with volume and height; matching area alone is not a complete paste check. |
| Alignment and shape | Position relative to the intended pad and abnormal deposit geometry. | Identify the permitted offsets and critical neighboring features. |
| Connected or missing paste | Regions flagged for missing deposits or unwanted paste connections. [S24] | Define review criteria and whether the board is held before placement. |
| Repeated variation | Patterns associated with specific apertures, board locations or consecutive prints. | Record the response and verify recovery without silently widening limits. |
Tell us which features need inspection, your sampling requirements and the reports you need. We will confirm these details in your quotation.
From a clear requirement to a documented decision.
- 01
Set the inspection reference
Match paste data, stencil revision, pad families and board support to the released assembly. Define how the reference deposit is calculated or established.
- 02
Validate the measurement program
Confirm the inspection regions, reference plane and limits for the actual board. Resolve false calls and exclusions before routine use.
- 03
Act on the print result
Review out-of-limit deposits and apply the approved hold, cleaning or reprint procedure. Investigate the relevant printing variables before releasing the board.
- 04
Confirm the next print
Reinspect corrected deposits and monitor the affected locations. Link the revised setup and disposition to the appropriate board or lot.
Use paste data to explain the process decision.
Agree which records must be retained. A result file should make it possible to understand why a board was released, held or reprinted.
- Print configuration
- Board/revision, side, stencil identifier, paste reference and SPI-program version.
- Measured location
- Pad or aperture reference, selected metric, reference value and applicable limits.
- Finding and response
- Out-of-limit condition, reviewed image, authorized adjustment or reprint decision.
- Recovery evidence
- Reinspection result and the traceable release status of affected boards.
Paste acceptance is not solder-joint acceptance.
SPI measures the printed deposit before components and reflow change it. It cannot establish final wetting, component polarity, hidden-joint condition or powered operation. Use the relevant downstream inspections and tests for those separate requirements. [S21] [S25] [S30]
3D Solder Paste Inspection FAQs
Find answers about inspection methods, reports and approvals before placing your order.
Where does SPI belong in the assembly sequence?
Specify it after paste printing and before placement, while the deposited surface remains accessible. Its purpose is to review the print rather than a completed solder joint.
Why measure volume as well as height and area?
They describe different aspects of the deposit. A useful inspection plan defines the relevant combination and its reference values instead of treating a single visual area check as full 3D evidence. [S23]
Can every pad use the same limits?
Do not assume so. Review limits for the actual aperture, pad family and process requirements. Record approved differences and validate the measurement method used.
Does SPI replace post-reflow AOI or X-ray?
No. Those methods address visible assembly features or hidden structures after soldering. A paste result is evidence from an earlier process stage. [S21] [S25]
Does a high paste reading always prove a stencil problem?
No. Investigate the setup, reference, board support and print conditions. Treat the reading as evidence to examine, not an automatic root-cause conclusion.
Can failed prints simply be reprinted?
Use an approved handling and cleaning/reprint procedure appropriate to the board and materials. Define the required reinspection before placement; do not overwrite the original disposition history.
Technical references
- [S21]Koh Young — Zenith S 3D AOI
- [S23]Koh Young America — SPI Machine: Buyer’s Checklist
- [S24]Nordson — SQ7000+ Multi Function AOI, SPI & CMM (PDF)
- [S25]Nordson — Automated X-ray Inspection Product Portfolio (PDF)
- [S30]NI — PCB Assembly Test Toolkit
Explore the inspection and testing references below. Include the applicable standards, acceptance criteria and required records with your enquiry so we can confirm the inspection plan for your board.