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AUTOMATED ASSEMBLY

For high-volume assembly most users will want to auto-place the modules. The

modules have been designed to maintain compatibility with reflow processing

techniques, however, due to the their hybrid nature certain aspects of the

assembly process are far more critical than for other component types.

Following are brief discussions of the three primary areas where caution must be

observed.

Reflow Temperature Profile

The single most critical stage in the automated assembly process is the reflow

process. The reflow profile below should not be exceeded since excessive

temperatures or transport times during reflow will irreparably damage the

modules. Assembly personnel will need to pay careful attention to the oven's

profile to ensure that it meets the requirements necessary to successfully reflow

all components while still remaining within the limits mandated by the modules

themselves. The figure below shows the recommended reflow oven profile for

the modules.

Shock During Reflow Transport

Since some internal module components may reflow along with the components

placed on the board being assembled, it is imperative that the modules not be

subjected to shock or vibration during the time solder is liquid. Should a shock

be applied, some internal components could be lifted from their pads, causing

the module to not function properly.

Washability

The modules are wash resistant, but are not hermetically sealed. Linx

recommends wash-free manufacturing, however, the modules can be subjected

to a wash cycle provided that a drying time is allowed prior to applying electrical

power to the modules. The drying time should be sufficient to allow any moisture

that may have migrated into the module to evaporate, thus eliminating the

potential for shorting damage during power-up or testing. If the wash contains

contaminants, the performance may be adversely affected, even after drying.

125

60

0

0

50

100

150

200

250

300

120

180

240

300

30

90

150

210

270

330

360

180

210

220

Time (Seconds)

Ideal Curve

Limit Curve

Forced Air Reflow Profile

1-1.5 Minutes

2-2.3 Minutes

Ramp-up

Preheat Zone

Cooling

Soak Zone

Reflow Zone

20-40 Sec.

2 Minutes Max.

Figure 19: Maximum Reflow Profile

PAD LAYOUT

The following pad layout diagram is designed to facilitate both hand and

automated assembly.

PRODUCTION GUIDELINES

The modules are housed in a hybrid SMD package that supports hand or

automated assembly techniques. Since the modules contain discrete

components internally, the assembly procedures are critical to ensuring the

reliable function of the modules. The following procedures should be reviewed

with and practiced by all assembly personnel.

HAND ASSEMBLY

The module’s primary mounting

surface is sixteen pads located on

the bottom of the module. Since

these pads are inaccessible during

mounting, castellations that run up

the side of the module have been

provided to facilitate solder wicking

to the module’s underside. This

allows for very quick hand soldering

for prototyping and small volume

production.

If the recommended pad guidelines have been followed, the pads will protrude

slightly past the edge of the module. Use a fine soldering tip to heat the board

pad and the castellation, then introduce solder to the pad at the module’s edge.

The solder will wick underneath the module providing reliable attachment. Tack

one module corner first and then work around the device taking care not to

exceed the times listed below.

Castellations

PCB Pads

Soldering Iron

Tip

Solder

Absolute Maximum Solder Times

Hand-Solder Temp. TX +225°C for 10 Seconds

Hand-Solder Temp. RX +225°C for 10 Seconds

Recommended Solder Melting Point +180°C

Reflow Oven: +220°C Max. (See adjoining diagram)

Figure 18: Soldering Technique

0.100"

0.070"

0.065"

0.610"

Figure 17: Recommended PCB Layout