Lead-Free Reflow Oven with Nitrogen Atmosphere for Medium-Sized Printed Circuit Boards “Salamander XNZ-725”

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Lead-Free Reflow Oven with Nitrogen Atmosphere forMedium-Sized Printed Circuit Boards “Salamander XNZ-725”

In the past two or three years, despite the fact that thelead-free mounting technology just began to be applied
to mass production of commonplace electronic products,
there is an urgent need for this technology to deal withprinted circuit boards (PCBs) having a high difficulty levelsuch as for automobiles and network servers where
extremely high-reliability is required. This is presumably
because the WEEE Directive and the RoHS Directive arescheduled to come into force soon.
Because its liquidus line is higher than that of the tinlead eutectic solder by 30~40°C, the lead-free solder oftin-silver alloys, which is becoming the worldwide standard, tends to have such problems as increasing temperature differences in component joints, insufficient solder
wettability and inadequate heat resistance of components, thus lowering the soldering yields.
Furukawa Electric has been supplying, after the company addressed the above-mentioned problems to devise
appropriate countermeasures, the Salamander XNK seriesof lead-free reflow ovens for large-sized PCBs to the global market with a focus on the domestic as well as Asianmarkets, thereby making a major contribution to eliminating Pb solders.
Recently, Furukawa Electric has developed the XNZ-725
model (Figure 1), an extension of the XNK series, forexclusive use for medium-sized PCBs. This is a modified
model, intended for universal use, of a high-performancemodel that was developed for automotive applications.
Main features of the machine will be presented below.

1.

IMPROVED BASIC HEATINGPERFORMANCE

using hot air. While heat transfer rate can be increased byraising the wind speed of hot air, this will cause the displacement or shifting of components, so that improving
the heating performance by means of wind velocity alone
is restricted to a certain extent. Conventional Salamander
ovens have adopted a nozzle flow system which can,while suppressing the horizontal wind speed that causes
the displacement of components, increase the heat transfer rate. In the XNZ-725 model, the nozzle flow system,
inherited from the conventional model, has been improvedby alternating the suction and blow nozzles in a matrix
configuration as shown in Figure 2, thereby increasing thetotal output area of the blow nozzles. This has brought
about an improvement in the uniformity of temperature,and the basic heating performance has been upgradedby about 30 %. Moreover, the improved heating performance enabled to manufacture various PCBs using thesame setting for soldering temperature, so that a considerable reduction in the setup time has been achieved.

2.

INCLUSION OF FORCED COOLINGMECHANISM AS STANDARDEQUIPMENT

The two-stage cooling mechanism of the XNZ-725 using
water is included as standard equipment in considerationof the heat resistance of sensitive components and operator's comfort. This enables cooling of the surface temperature of a 1.6-mm thick glass-epoxy PCB down to 100°C
or lower at the reflow oven exit, realizing a cooling gradient of 4°C/sec at the maximum. See Figure 3.

To decrease the temperature difference in the components joints, it is required to increase the heat transfer rate

Suction nozzle

Figure 2Figure 1Appearance of Salamander XNZ-725PT.

Blow nozzle

Appearance of hot-air nozzle panel. The blow andsuction nozzles are alternately arrayed.

Furukawa Review, No. 28

200570Lead-Free Reflow Oven with Nitrogen Atmosphere for Medium-Sized Printed Circuit Boards “Salamander XNZ-725”

300

Front left
(fixed side)
Front center
Front right(moving side)
Center left
(fixed side)
CenterCenter right(moving side)
Rear left(fixed side)
Rear center
Rear right(moving side)

Temperature (°C)

250200150100030 60 90 120 150 180 210 240 270 300 330 360 390 420
Time (sec)Figure 3

3.

Example of temperature profile measurements.

FLUX COLLECTION

4.

ZONE COFIGURATION

Figure 5 shows the zone configuration of the XNZ-725
consisting of seven heating zones and two cooling zones
in addition to a flux collection system installed at the entryand exit.

7.

A new flux collection system of centralized configuration
has been adopted to prevent deposition of flux fumes
evaporated from the PCBs. Ease of maintenance has
been greatly improved due to the new system whereby
flux collection at the entry and exit is enhanced thus
reducing the intermediate collection spots.

COMPACT DESIGN

In line with the general movement of mounting systems
toward medium-sized PCBs, the XNZ-725 specializes inthis size, and succeeded in the footprint reduction whileachieving performance improvements above mentioned.
The total length of the oven is about 5 m, i.e. 20~100 cm
shorter than conventional ovens of the XNK-series.

6.

5005.

SPECIFICATION

Table 1 shows the specifications of the XNZ-725.
Table 1

Outline specifications

Length5070 mmWidth

1300 mm

Height1400 mm

Outer dimensions

Maximum PCB width

IMPROVED EASE OF OPERATION

250 mmTop and bottom clearance

A high-performance microcomputer with a touch panel
has been employed to ensure ease of operation as goodas or better than that of personal computers, while achieving upgraded reliability without using a HDD. See Figure
4.

Operation screen

Number of zones

Top: 15 mm, Bottom: 15 mm (standard)

Heating7CoolingPower supply
Power consumption

2AC 200 V, 3 phase
52 kVA max. including chiller

Weight2,200 kg

For more information, please contact:
Electronics Sales Department, Electronics Components
Division
TEL: +81-463-24-8362
FAX: +81-463-24-8376
Surface Mounting Engineering Department, Electronics
Components Division
TEL: +81-463-24-8371~3 FAX: +81-463-24-8376

Heater logging screen
Figure 4Operation panel.
* Length of zone unit: 350 mm
Seven heating zones

Two cooling zones

Forced cooling unit

Flux collection unit

Flux collection unit

Figure 5

Zone configuration.

Furukawa Review, No. 28

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