This document provides guidance on properly setting up and understanding the key parts and parameters of a wave soldering process. It emphasizes the importance of understanding all variables and requirements before attempting fixes. Key parts discussed include the conveyor, flux applicator, preheaters and wave. Correct setup of conveyor speed, angle and clearance, as well as preheat temperature profiles, flux application and wave characteristics are vital to ensuring proper soldering with no defects. Verifying the wave shape with glass is also recommended.

1. ABSOLUTE BASICS TO SUCH A SIMPLE PROCESS…
YEAH RIGHT

2. BUT… THIS IS SO SIMPLE… JUST ADD FLUX…
• By now you probably know better that many of the shortcut-eager quick-
fixers will just give you a temporary fix but not a solution…
• So if really want to control your process, drive scrap down and bring your
process under control maybe you want to start reading.
• In general a quick fix implies no thinking, and without analysis is like applying
yourself a band aid to stop your neighbor’s bleeding.

3. UNDERSTAND YOUR PROCESS FIRST!!!
• There are many variables involved so make sure you UNDERSTAND FIRST
• Second… Analyze from the standpoint of requirements so you can figure out
what you might be missing

4. REQUIREMENTS
• The surfaces to be soldered must be free of
oxides and other contaminants in order to achieve proper physical and electrical
bond
• The temperature difference between the unit to solder and the molten solder must not
be so dramatic to produce CTE mismatch (product thermal cracking)
• Must have one (1) solder joint per pad/pin, no more (bridges) and no less (skips)
• No foreign materials present or undesired residues resulting from the process
• Components must be present, be the right component, on
the correct position and properly connected

5. PARTS OF THE PROCESS/MACHINE
• Conveyor: as it takes the product across the different stages it is co-
responsible for the results as it interacts with all requirements.
• Flux Applicator: Applies the solder facilitator. (simple!? )
• Preheating: Prepares Product and Flux for the arrival of solder.
• Wave Solder: the hot mean molten metal that we need to apply to the
electro-mechanical bond points.

6. CONVEYOR SETUP PARAMETERS
• Inclination angle between 5°-7° (typically 6°) to control wave/pcb contact
surface
• Transport speed determines EVERYTHING (fluxing, preheat profile, wave
dwell)
• Leveling front-to-back determines homogeneous contact with flux & wave
• Parallelism affects board flatness and support.

7. CONVEYOR FINGER SETUP
• Different types of fingers
• V grooved fingers are to provide some
pressure to hold PCB
• L-Shape fingers can have fingers “loose”
• Inverted spring tab keeps PCB from being
lifted by the wave
• Critical: all fingers must be in-line
• Board must sit on top of the L and does not
need to be pushed or held under pressure.

8. HOW TO SET UP CONVEYOR
• Leveling
• In-to-Out 6°
• Front-Back Level Flat
• Clearance from bottom of PCB to:
• Fluxer nozzle 2.5mm < Clearance < 8mm
• Wave nozzle 2.5mm < Clearance < 8mm
• Conveyor Width (L-Shaped) must be just sufficient to hold part from falling but no
compression.

9. FOAM FLUXER SETUP
• MUST be leveled also to produce homogeneous flux application
• Nozzle-to-board clearance
• Bubble Size homogeneous and as small as
possible
• Air Supply dry and clean
• Controls for pressure and air volume are used to maintain
bubble size and foam column height
• Air Knife setup critical
• Avoids excess flux
• Pushes flux up to top side pads
• PCB must not be dripping of flux when it leaves fluxer
Unleveled
Conveyor-fluxer

10. AIR KNIFE SETUP
• Angle too shallow or too much air
• Collapses Foam Column
• Board underfluxed
• Angle too steep or little air
• Excess flux on top (steep angle)
• Excess flux underneath dripping into
preheaters (risk of fire)

11. CONTROLLING FLUX
• VOC / Solvent based flux evaporates at
varying rates depending on temperature,
atmospheric pressure and air flow
• Must keep constant control over solids content
as solvent evaporates
• It will affect solder results, and residues
• Foam consistency changes and alters bubble size.
• The lower the air flow the lower the evaporation, but will also lower foam flux column
height.
• Maintain aerator wet in solvent at all times! Otherwise it will clog pores with solids

12. PREHEATERS
• Infrarred heaters (radiant)
• Heat bounces from metal shiny areas
• Dull areas (solder mask) raise higher
temperatures
• Heater temperature >6x over PCB
temperature
• Convection heaters
• Slower heat transfer rates
• Homogenous temperatures
• Heater temperature ~1:1 to PCB

13. PREHEAT SETUP
• Heat up ramp rates must meet Flux specifications (typically 2-3°C/Sec)
• Direct relationship with conveyor speed
• faster speeds = lower ramp rates & low exit temperature
• lower speeds = higher ramp rates & higher exit temperature)
• Exit temperature must also be met.
• Temperature too high or too soon before wave will consume flux before wave
• Temperature too low will leave too much flux on board (spatter, outgassing & solder
balls)
• Temperature is evaluated at Top Side!!!

14. WAVE SETUP FOR ASYMMETRIC WAVE
• Wave nozzle must be leveled
• Wave height (nozzle to top of wave)
• Minimize height to reduce dross
• Wave height must be at least 50%
of PCB depth (relation to conveyor)
• Back flow must be minimal.
• Wave MUST be perpendicular to
conveyor (consistency in height,
penetration and contact dwell time)

15. SOLDER WAVE CHARACTERISTICS
• Front cascade must be laminar across PCB
• Flow around the edges of nozzle (front and back) is turbulent and will not
ensure penetration and debridging
• Backflow speed must be equal to PCB speed to ensure debridging and excess
removal
• Liquid temperature too low will also cause bad solder results
• Wave height above nozzle >2.5mm but as low as possible prevent component
terminals from hitting the nozzle

16. USING GLASS TO VERIFY WAVE
• HIGH IMPORTANCE:
• Preheat glass or it will shatter into pieces
• Conveyor must not compress glass
• Perpendicular contact area is relevant
• Cannot determine laminar flow you must ensure
PCB is at least 6mm inside the nozzle edges

17. OTHER CONSIDERATIONS
• DFM
• Pin to hole ratio desirable .008 to .020”
(0.2 to 0.5mm) for proper filling
• Lead to pad ratio >2:1
• Lead protrusion: shorter is better for
component lifting reduction and solder bridging
• Topside pad reduction helps