CN1450612A - Method for forming convex point on back side of single side flexible sustrate - Google Patents

Abstract

A method for forming convex at the back of single-side flexible substrate applies complex flexible substrate composed of a flexible substrate and synthetic rubber belt surface layer with fixed soldered disk, electrode or elements on the front. The process steps are as follow: 1. to punch blind holes on complex flexible substrate with laser 2. to fill soldered paste to the blind holes with print plate 3. to melt the soldered paste to soldered ingot by high temperature reflow soldering 4. to eliminate the synthetic rubber belt surface 5. to solder to convex by second time of high temperature backflow soldering.

Description

Form the method for salient point at the single-sided flexible substrate back

Technical field

The invention belongs to printed circuit and microelectronic element encapsulation field, particularly introduce the encapsulating structure of salient point and the manufacturing process of salient point at the single-sided flexible substrate back.

Background technology

The High Density Packaging Technology of a new generation comprises BGA Package Ball-Grid-Array with the main flow that is encapsulated as of face array structure, BGA), chip size packages (Chip-Scale-Package, CSP), flip-chip (Flip-Chip) technology etc.The Flip-Chip Using technology of broad sense refers to engage with substrate by metallic conductor in ventricumbent mode after the chip upset, realizes interconnection.This technology also is incorporated in the interconnect package of MEMS (micro electro mechanical system) (MEMS).The MEMS device many times will adopt the flexible base, board structure (FlexSubstrate) of BGA form, to satisfy the needs of practical application.The one side of flexible base, board can be pad, electrode, circuit or senser etc., also can connect another MEMS device; And its back side generally is the light face, and without any components and parts, the present invention will introduce the metallic conductor of interconnection at the back side of single-sided flexible substrate.Generally speaking, the interconnecting metal conductor is comparatively advanced with metal salient point (Metal Bump) technology of face array.The technology of existing widely used preparation salient point is to adopt chemical plating or electronickelling/gold (Ni/Au) to form salient point bottom metal layers (Under BumpMetallurgy earlier, UBM) cooperate the mode of printing with paste to plant ball again, " form the method for unleaded bump interconnect " as the patent No. 01115321.0, the main manufacture process of its salient point is as follows:

Going up at the aluminium (Al) on wafer (Wafer) surface earlier adopts chemical plating or electronickelling/gold to form the UBM layer; Apply one deck photoresist (photo-resist) and give preheating at crystal column surface; Above wafer, intercept and the exposure imaging imaging, make on UBM layer position and form blind hole with suitable mask (Mask); Utilize brush board that soldering paste is inserted in the blind hole then, make soldering paste be melt into the weldering ingot through the high temperature reflux weldering, again this photoresist is removed back and cleaning with chemical reagent, only stay the weldering ingot of projection on the wafer, this weldering ingot promptly forms spherical soldered ball after the second time, the high temperature reflux weldering was handled.There is following shortcoming in this kind salient point preparation method: photoresist needs to spend the stiff time after covering; The development imaging process must be made mask in addition, has increased manufacturing cost; Photoresist must be removed with chemistry or physics mode after the reflow treatment for the first time, and whole process is loaded down with trivial details and time-consuming.And, may not adopt this technology when being packaged with, because some MEMS senser requires to keep solid-state operation for MEMS.

Summary of the invention

The invention provides a kind of method that forms salient point at the back side of single-sided flexible substrate, its objective is at the back side of single-sided flexible substrate and introduce salient point, for technology such as MEMS provide the packaging of flexibility, and simplify preparation process effectively, save time and keep solid-state operation.

A kind of method at single-sided flexible substrate back formation salient point of the present invention is inserted soldering paste, twice high temperature reflux weldering formation salient point by brush board, comprises the steps: in regular turn

(1) processing object is the composite and flexible substrate, comprises flexible base, board and synthetic adhesive tape top layer, and the flexible base, board front is fixed with pad, electrode or components and parts;

(2) beat blind hole with laser on the composite and flexible substrate, hole depth is till pad, electrode or the components and parts in flexible base, board front;

(3) utilize brush board that soldering paste is inserted the blind hole position; (4) the high temperature reflux weldering is melt into the weldering ingot with soldering paste; (5) remove synthetic adhesive tape top layer; (6) high temperature reflux weldering for the second time forms salient point.

The invention provides a kind of back side at the single-sided flexible substrate and introduce the encapsulating structure of salient point, this encapsulating structure can be used for the single face encapsulation, also can carry out double-faced packaging, for application technologies such as MEMS provide a kind of flexibility, the high-density packages structure.The present invention also provides a kind of single-sided flexible substrate back to form the method for salient point, adopt the composite and flexible substrate, the synthetic adhesive tape of its top layer good heat resistance has replaced traditional photoresist, and punch with the program control laser positioning, behind printing soldering paste, high temperature reflux, directly tear adhesive tape off and can carry out the backflow second time, can reduce multiple working procedure effectively, save time and keep solid-state operation, need not to lose time and wait for cleaning, the air-dry time of chemical agent.The gained salient point directly links to each other with the pad/electrode in flexible base, board front, and interconnect strength is good, and contact resistance is little.

Description of drawings

Fig. 1-Fig. 6 forms salient point process schematic diagram for this method, wherein

A kind of three layers of composite and flexible substrate that Fig. 1 adopts for this method,

Fig. 2 is at single-sided flexible substrate back laser drilling schematic diagram,

Fig. 3 goes into the soldering paste schematic diagram for utilizing brush board to brush in blind hole,

Fig. 4 welds the ingot schematic diagram for through high temperature reflux soldering paste being melt into,

Fig. 5 tears schematic diagram for adhesive tape is synthesized on the top layer,

Fig. 6 is through high temperature reflux formation second time salient point schematic diagram.

Symbol is among the figure:

Pad (can be other electrodes, senser etc.) 1, flexible base, board 2, rigid resin plate 3, synthetic adhesive tape 4, laser beats blind hole 5a, fill up blind hole 5b behind the soldering paste, weld ingot 5c, soldering paste 6, brush board 7, salient point 8.

Embodiment

With reference to Fig. 1-process schematic diagram that forms salient point at the back side of single-sided flexible substrate shown in Figure 6.The substrate that one embodiment of the present invention adopted is three layers of composite and flexible substrate, as shown in Figure 1.Be fixed with pad 1 or other electrodes, circuit and components and parts on flexible base, board 2 fronts of the bottom, intermediate layer 3 is the rigid resin plate, and it can strengthen the rigidity of whole base plate, thereby makes substrate that better operability be arranged.The top layer of substrate engages with the intermediate layer closely for synthetic adhesive tape 4, synthetic adhesive tape 4, but directly tears off than being easier to, and has the thermal endurance and the stability of getting well.With reference to Fig. 2-Fig. 6, concrete manufacture process is:

A, employing program control laser positioning punching technology, the punching of position shown in the dotted line in Fig. 1.Punching will

Three layers of composite and flexible substrate 2,3,4 are punched fully, and owing to the selectivity of laser to material, beat

Kong Buhui causes damage to pad 1 or other components and parts.After punching is finished, form shown in Figure 2

Blind hole 5a.

B, utilize brush board 7 that soldering paste 6 is inserted in the blind hole, form the blind hole 5b that fills up soldering paste, as shown in Figure 3.

C, make soldering paste in the blind hole be melt into weldering ingot 5c through high temperature reflux, as shown in Figure 4.

D, will synthesize adhesive tape 4 again and directly tear off, only stay the weldering ingot 5c of projection on the substrate, as shown in Figure 5.

E, after the second time, high temperature reflux was handled, this weldering ingot 5c forms the salient point of sphere on rigid resin plate 3

8, as shown in Figure 6.

Claims (1)

1. the method at single-sided flexible substrate back formation salient point is inserted soldering paste, twice high temperature reflux weldering formation salient point by brush board, comprises the steps: in regular turn

(1) processing object is the composite and flexible substrate, comprises flexible base, board and synthetic adhesive tape top layer, and the flexible base, board front is fixed with pad, electrode or components and parts;

(2) beat blind hole with laser on the composite and flexible substrate, hole depth is till pad, electrode or the components and parts in flexible base, board front;

(3) utilize brush board that soldering paste is inserted the blind hole position;

(4) the high temperature reflux weldering is melt into the weldering ingot with soldering paste;

(5) remove synthetic adhesive tape top layer;

(6) high temperature reflux weldering for the second time forms salient point.

Images