WaveSolder Briefing

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