Method of resin molding

The method of resin molding is capable of preventing molded products from forming resin flash on their surfaces. The method comprises the steps of: covering over a parting face, of at least one of molding dies with release film; clamping a work piece, with the release film, by the molding dies; and filling the melted resin in the molding section of the molding die, wherein the release film is tightly pressed on a surface of a part of the work piece, which is exposed after molding, in the clamping step. By pressing the release film on the surface of the part of the work piece, the release film prevents the melted resin from invading into a gap between the release film and the work piece, so that no resin flash is formed on the surface of the work piece.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a method of resin molding and a resin
 molding machine for the method.
 2. Description of Related Art
 The applicant of the present invention has invented molding machines, in
 which parting faces of molding dies are covered with release film while
 molding (see Japanese Patent Kokai Gazettes No. 8-142105, No. 8-142109 and
 No. 9-57785). In the conventional resin molding machines, the parting
 faces, which include cavities, of the molding dies are covered with the
 release film, then resin molding is executed in the cavities. By using the
 release film, resin can be solidified without sticking to the molding
 dies. Further, molded products can be easily ejected from the molding
 dies, so no ejector pins are required and structures of the molding dies
 can be simpler. Many types of resin, e.g., tablet, pellet, liquid, can be
 employed in the conventional molding machines.
 FIG. 31 is a front view of a conventional resin molding machine, in which
 no release film is used; FIG. 32 is a plan view thereof. In the resin
 molding machine, a part "A" is a press section for clamping and molding
 work pieces, e.g., lead frames, with resin; a part "B" is a work feeding
 section, in which the work pieces are fed; a part "C" is a tablet feeding
 section, in which resin tablets are fed; a part "D" is a loading section,
 in which the work pieces and the resin tablets are arranged and set into a
 molding die; a part "E" is an unloading section, in which molded products
 are taken out from the molding dies and disused resin of the products are
 removed; and a part "F" is an accommodating section for accommodating the
 molded products.
 As described above, the resin molding machine using the release film has
 some advantages. For example, the molded products can be easily ejected
 from the molding die, and the structures of the molding dies can be
 simpler. The structure of the resin molding machine using the release film
 is quite different from that of the resin molding machine using no release
 film. To execute the method of resin molding with the release film, the
 old molding machines must be fully replaced, so the equipment cost must be
 quite higher.
 However, quality of the molded products, which are molded by the resin
 molding machine shown in FIGS. 31 and 32, is not fully satisfied. In the
 case of molding lead frames with resin, the resin molding machine has the
 following disadvantages: resin flash is apt to be formed on the surface of
 the molded product; thickness of the molded products are not fixed; and it
 is difficult to mold thinner products.
 In FIGS. 33-35, a work piece (a lead frame of transistors) 200 having heat
 sinks 202 are molded with resin. The work piece is clamped by molding dies
 and molded by filling the resin in cavities 206 via gates 204. Dam blocks
 208 fill spaces between adjacent workpieces 200 so as not to leak the
 resin. The height of the dam blocks 208 is slightly lower than the
 thickness of the work piece 200 so as not to damage the opposite parting
 face of the molding die when the molding dies clamp the work piece 200.
 Thus, thin resin flash is formed between the dam blocks 208 and the
 opposite parting face.
 The resin flash 210 is formed between the dam block 208 and the work piece
 200 and on outer faces of the heat sinks 202. The resin flash 210 is also
 formed in the peripheral of resin paths connecting pots to the cavities
 206, e.g., the gates 204, and in the peripheral of culls 212. This is
 because securely clamping the work piece 200 has priority over preventing
 the resin flash, so the resin flash 210 is apt to be formed between the
 molding dies.
 In FIG. 36, a work piece (a plastic circuit board of BGA) 200 is molded
 with resin. The resin flash 210 is formed in the vicinity of molded parts
 214. The thickness of the plastic circuit boards is not fixed, so all
 plastic circuit boards cannot be clamped with fixed clamping force.
 Therefore, resin flash maybe formed on surfaces of the molded products.
 If the molded products have resin flash formed thereon, the step of
 removing the resin flash is required after a molding step. Furthermore,
 the resin flash is scattered in all directions when the molded products
 are taken out from the molding die; the scattered resin causes troubles.
 Further, if the resin flash is formed on a surfaces of an electric
 terminal, the molded product cannot be electrically connected.
 SUMMARY OF THE INVENTION
 An object of the present invention is to provide a method of resin molding
 and a molding machine, which are capable of preventing molded products
 from forming resin flash on their surfaces.
 To achieve the object, the method of the present invention comprises the
 steps of:
 covering over a parting face, of at least one of molding dies with release
 film;
 clamping a work piece, with the release film, by the molding dies; and
 filling the melted resin in the molding section of the molding die,
 wherein the release film is tightly pressed on a surface of a part of the
 work piece, which is exposed after molding, in the clamping step.
 By pressing the release film on the surface of the part of the work piece,
 the release film prevents the melted resin from invading into a gap
 between the release film and the tilt work piece, so that no resin flash
 is formed on the surface of the work piece.
 In the method, the part of the work piece, which is exposed after molding,
 may be located in the molding section of the molding die when the molding
 dies clamp the work piece.
 In the method, the part of the work piece, which is exposed after molding,
 may be located outside of the molding section of the molding die when the
 molding dies clamp the work piece.
 In the method, the molding section may be formed in the parting face of one
 of the molding dies, wherein a parting face of the other molding die is a
 flat face on which the release film is fed.
 In the method, an escaping section, in which the release film can be
 accommodated, may be formed in the parting face of the molding die,
 whereby deformation of the work piece is prevented when the molding die
 presses the release film on the surface of the work piece.
 In the method, the part of the work piece, which is exposed after molding,
 may be an electric terminal.
 In the method, the part of the work piece, which is exposed after molding,
 may be a heat radiating part.
 In the method, the part of the work piece, which is exposed after molding,
 may be an optical transparent part.
 Furthermore, the resin molding machine of the present invention comprises:
 a press section including a couple of molding dies for clamping and molding
 a work piece to be molded, and a couple of platens to which the molding
 dies are respectively attached;
 a loading section for setting the work piece and a resin material into the
 molding die of the press section;
 an unloading section for conveying a molded product from the press section;
 an accommodating section for accommodating the molded product, in which
 disused resin has been removed;
 a film feeding mechanism being provided to one of the platens, the film
 feeding mechanism feeding release film to cover over a parting face, of at
 least one of the molding dies; and
 an air sucking mechanism for fixing the release film on the parting face of
 the molding die by air suction.
 The release film is fed onto the parting face of the molding die by the
 film feeding mechanism, and the molding section therein is covered with
 the release film. By the release film, the work piece can be molded
 without sticking the resin on the molding section.
 In the resin molding machine, the loading section may be located on one
 side of the press section, the unloading section may be located on the
 other side thereof, and
 the film feeding mechanism may feed the release film in the direction
 perpendicular to a line connecting the loading section and the unloading
 section.
 In the resin molding machine, the film feeding mechanism may comprise:
 a feeding roller on which long new release film has been wound, the feeding
 roller being provided on one side of the molding dies;
 a collecting roller for winding used release film, which has passed over
 the parting face of the molding die, the collecting roller being provided
 on the other side of the molding dies; and
 a driving section for rotating the feeding roller and the collecting roller
 according to molding action of the resin molding machine.
 In the resin molding machine, the width of the release film may be designed
 to cover over the whole parting face of the molding die.
 In the resin molding machine, the width of the release film may be equal to
 that of the work piece, and
 the release film may be fed to a position corresponding to the work piece.
 The resin molding machine may further comprise lock blocks being
 respectively provided to the molding dies and capable of engaging with
 each other to correctly position the molding dies when the molding dies
 clamp the work piece, the lock blocks being arranged not to interfere with
 the release film covering the molding die.
 In the resin molding machine, an escaping section, in which the release
 film can be accommodated, may be formed in the parting face of the molding
 die.
 In the resin molding machine, a drawing groove, into which a slackened part
 of the release film is drawn by air suction, may be formed in a peripheral
 of the molding section of the molding die.
 In the resin molding machine, a drawing groove, into which a slackened part
 of the release film is drawn by air suction, may be formed in a peripheral
 of the escaping section of the molding die.
 Further scope of applicability of the present invention will become
 apparent from the detailed description given hereinafter. However, it
 should be understood that the detailed description and specific examples,
 while indicating preferred embodiments of the invention, are given by way
 of illustration only, since various changes and modifications within the
 spirit and scope of the invention will become apparent to those skilled in
 the art from this detailed description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Preferred embodiments of the present invention will now be described in
 detail with reference to the accompanying drawings.
 [First Embodiment]
 A resin molding machine of the present embodiment is shown in FIGS. 1 and
 2. A basic structure of the resin molding machine is almost the same as
 that of the conventional resin molding machine. Namely, the molding
 machine has: a press section "A"; a work feeding section "B"; a tablet
 feeding section "C"; a loading section "D" in which work pieces and resin
 tablets are arranged and set into a molding die; an unloading section "E"
 in which molded products are taken out from the molding dies; and an
 accommodating section "F" in which the molded products are accommodated.
 A characterized point of the resin molding machine of the present
 embodiment is a film feeding mechanism "G", which is provided to an upper
 side of the press section "A". The press section "A" has a fixed platen 5,
 which holds an upper base 22a and an upper molding die 20a. The film
 feeding mechanism "G" is held by the fixed platen 5. The film feeding
 mechanism "G" feeds the release film 50 from a front side of the press
 section "A" to a rear side thereof.
 As shown in FIG. 2, the film feeding mechanism "G" includes a feeding
 roller 6, round which the new release film 50 is wound, and a collecting
 roller 7, which collects the used release film 50. The feeding roller 6 is
 provided on the front side of the press section "A"; the collecting roller
 7 is provided on the rear side thereof. A driving section synchronously
 drives the rollers 6 and 7 with molding action of the machine, so the
 release film 50 is intermittently fed a prescribed length. In the present
 embodiment, the width of the release film is designed to cover over a
 whole parting face of the molding die.
 The release film 50 is capable of resisting temperature of the molding
 dies, which are heated to mold work pieces. The release film 50 is easily
 peeled off from the solidified resin. The release film 50 has enough
 flexibility so as to cover and protect the surfaces of the work pieces and
 to act as a cushion. Thus, FEP film, PET film, glass cloth including
 fluorine, film of polyvinylidene chloride, FETF film, etc. can be used as
 the release film 50.
 A summarized method of resin molding by the resin molding machine will be
 explained. The resin tablets, which have been fed by the tablet feeding
 section "C", are accommodated in a resin holder and conveyed to a position
 under the loading section "D". The work pieces, e.g., lead frames, are
 conveyed from the work feeding section "B" to the loading section "D".
 In the loading section "D", the work pieces and the resin tablets are
 transferred to a loader.
 The work pieces and the resin tablets are conveyed to the press section "A"
 by the loader. Furthermore, the resin tablets are respectively set in pots
 of the molding die; the work pieces are set on the molding die. The work
 pieces are clamped, by the molding dies of the press section "A", together
 with the release film 50. The melted resin is sent from the pots to
 molding sections (cavities) to mold or encapsulate the work pieces.
 After molding, the molding dies are opened, and molded products, which have
 been molded in the press section "A", are conveyed to a degating section
 "H". At the degating section "H", disused resin, which is stuck to the
 molded product, is removed, and the molded products are accommodated in
 the accommodating section "F".
 In the case of feeding the release film 50 to the upper molding die 20a,
 the parting face of the upper die 20a need not be cleaned, so a cleaner of
 the unloading section "E" is capable of cleaning a parting face of the
 lower molding die 20b only.
 The release film 50, which is covering over the molding die, is renewed for
 each molding cycle or a prescribed number of molding cycles. When the new
 release film 50 is fed to the molding die, the release film 50 is slightly
 separated away from the parting face of the molding die by a moving
 mechanism, which is capable of vertically moving the release film 50.
 FIGS. 4 and 5 show lock blocks 70a, 70b, 72a and 72b of the molding dies
 20a and 20b, which allow the release film 50 to move from the front side
 of the molding dies to the rear side thereof. When the work pieces are
 clamped by the molding dies 20a and 20b, the lock blocks 70a and 72a and
 the lock blocks 70b and 72b are mutually engaged so as to correctly
 position the molding dies 20a and 20b. Arrangement of the lock blocks 70b
 and 72b of the lower die 20b is shown in FIG. 4. FIG. 5 is a sectional
 view of the molding dies 20a and 20b, in which the release film 50 is sent
 in the direction perpendicular to the surface of the drawing sheet, and in
 which an engaging state of the lock blocks 70a and 70b of the molding dies
 20a and 20b is shown on the right side of a center line CL.
 To correctly position the molding dies 20a and 20b, the positions of the
 centers of the molding dies, in the X- and the Y-directions, are mutually
 coincided by engaging the lock blocks 70a and 72a of the upper die 20a
 with the lock blocks 70b and 72b of the lower die 20b. In the present
 embodiment, the lock blocks 70a, 70b, 72a and 72b must be arranged so as
 not to interfere with the release film 50, which has been fed on the
 parting faces of the molding dies. Thus, the lock blocks 70b are
 respectively located at both ends, in the X-direction, of the lower die
 20b, and their shape allows the release film 50 to move in the X-direction
 (see FIG. 5).
 As shown in FIG. 5, engaging projections 71 are respectively provided to
 each end of the lock blocks 70b. The projections 71 are located outside of
 an area in which the release film 50 passes, so that the molding dies 20a
 and 20b can be closed without interfering with the release film 50.
 Note that, the lock blocks 72b arranged in the Y-direction may be located
 at centers of edges, in the X-direction, of the lower die 20b.
 Successively, the method of resin molding will be described in detail with
 reference to FIGS. 6 and 7.
 The work pieces 10 are circuit boards of BGAs. Semiconductor chips 12 are
 respectively mounted on bottom faces of the work pieces 10. The
 semiconductor chips 12 will be molded or encapsulated with the resin;
 upper faces of the work pieces, on which lands have been formed as
 electric terminals, will be exposed. There are formed cavities 28 for
 resin molding in the lower die 20b. The release film 50 is fed to the
 upper die 20a. Note that, plastic circuit boards, tape-formed substrates,
 etc. can be molded as the work pieces 10.
 In FIG. 6, a state of opening the molding dies 20a and 20b is shown on the
 left side of the center line CL; a state of closing the molding dies 20a
 and 20b and filling the resin in the cavities 28 is shown on the right
 side of the center line CL. The upper die 20a is held by the upper base
 22a; the lower die 20b is held by a lower base 22b. Heaters 24 are
 provided in the dies 20a and 20b so as to heat the dies. The lower base
 22b is held by a movable platen, which is capable of vertically moving, so
 that the lower die 20b is capable of vertically moving so as to open and
 close the dies 20a and 20b.
 Two work pieces 10, each of which is formed into a rectangle, are
 respectively set on each side of a line of the pots 26. The work pieces 10
 are correctly positioned by guide pins 27. The cavities 28 of the lower
 die 20b are located to correspond to the semiconductor chips 12 of the
 work pieces 10. Ejector pins 30 are provided in the lower die 20b and
 located to correspond to the cavities 28. Upper end faces of the ejector
 pins 30 coincide with inner bottom faces of the cavities 28. When the
 molded products are taken out from the cavities 28, the ejector pins 30
 upwardly eject the molded products therefrom.
 A plunger 32 is vertically slidably provided in each pot 26. In FIG. 6, the
 resin tablet 34 is set in the pot 26 (an example shown on the left side of
 the center line CL); the resin pellets 36 are supplied in the pot 26 (an
 example shown on the right side of the center line CL). The pots 26 are
 connected to the cavities 28 by resin paths, each of which includes
 runners 38 and gates 40.
 The work pieces 10 are molded in the lower die 20b only, so the parting
 face of the upper die 20a is a flat face with no cavities. As described
 above, the width of the release film 50 is designed to cover over the
 whole parting face of the upper die 20a. The release film 50 is fixed, by
 air suction, on the parting face.
 As shown in FIG. 6, air is sucked through air sucking holes 42 so as to fix
 the release film 50 on the parting face of the upper die 20a. The air
 sucking holes 42 are connected to air paths 44 in the upper die 20a. The
 air paths 44 are connected to an air sucking mechanism (not shown). The
 air sucking mechanism is located outside of the resin molding machine.
 Note that, the air sucking machine may be provided in the resin molding
 machine.
 In FIG. 7, the release film 50 is fed on the parting face of the upper die
 20a. The release film 50 covers over the whole parting face. Lines of the
 air sucking holes 42 are arranged in the longitudinal direction of the
 upper die 20a. The work pieces 10 are arranged in the same direction. Note
 that, symbols 27a indicate guide holes, into which the guide pins 27 will
 be inserted to correctly set the work pieces 10.
 In the case of having other air sucking means, e.g., sucking holes in the
 cavities 28, drawing grooves into which a slackened part of the release
 film 50 is drawn by air suction, each group of the air sucking means are
 respectively connected to an independent air sucking mechanism. To
 immediately resume air suction for fixing the release film 50, a mechanism
 capable of extinguishing negative pressure is preferably provided.
 As described above, the parting face of the upper die 20a is basically
 flat, but there are formed escaping sections (escaping cavities) 52, which
 are capable of absorbing the thickness of the release film 50, in the
 parting face thereof. The escaping sections 52 are located to face the
 cavities 28 of the lower die 20b. The depth of the escaping section 52 is
 slightly shallower than the thickness of the release film 50.
 While clamping the work pieces 10, a clamping force is applied to clamping
 regions in the parting faces of the dies 20a and 20b, which enclose edges
 of each cavity 28 while closing the dies 20a and 20b and which have a
 prescribed width. By concentrating the clamping force to the clamping
 regions enclosing the cavities 28 while molding, no resin leaks from the
 cavities 28. Since the work pieces 10 are not held in the cavities 28, the
 work pieces 10 are apt to be excessively pushed and deformed while
 clamping the work pieces 10 due to the thickness of the release film 50.
 But, in the present embodiment, parts of the release film 50 corresponding
 to the cavities 28 are accommodated in the escaping sections 52, so that
 deformation of the work pieces 10 can be prevented. Since the release film
 50 has enough softness, so the depth of the escaping section 52 may be
 slightly shallower than the thickness of the release film 50.
 The molding action of the molding machine will be explained.
 Firstly, the work pieces 10 are correctly set in the lower die 20b by the
 guide pins 27. In the present embodiment, a couple of work pieces 10 are
 set in the lower die 20b. While the molding dies 20a and 20b are opened,
 the release film 50 is fixed on the parting face of the upper die 20a by
 air suction. The new release film 50 is drawn a prescribed length from the
 feeding roller 6 and fixed on the parting face of the upper die 20a by
 sucking the air from the air sucking holes 42.
 The resin for molding is supplied into the pots 26. In FIG. 6, the case of
 setting the resin tablet 34 in the pot 26 is shown on the left side of the
 center line CL. On the left side of the center line CL, the dies 20a and
 20b are opened, the work piece 10 and the resin tablet 34 are set in the
 lower die 20b, and the release film 50 is fixed on the parting face of the
 upper die 20a.
 Next, the work pieces 10 are clamped by the dies 20a and 20b. In the
 present embodiment, the lower die 20b is a movable die, so the lower die
 20b is moved upward to clamp the work pieces 10. The release film 50 is
 sandwiched between the work pieces 10 and the upper die 20a. The cavities
 28 are formed in the lower die 20b.
 After clamping the work pieces 10, the resin, which has been melted in the
 pots 26, is exerted in the pot 26 by moving the plungers 32 upward. In
 FIG. 6, on the right side of the center line CL, the resin 35 is fully
 filled in the cavity 28a. The resin 35 is introduced into the cavity 28a
 via the runner 38 and the gate 40. The upper face of the work pieces 10
 facing the upper die 20a is perfectly covered with the release film 50, so
 the lower faces of the work pieces 10, on which the semiconductor chips 12
 have been respectively mounted, are encapsulated with the resin.
 After solidifying the resin 35 in the cavity 28a, the dies 20a and 20b are
 opened, and the molded products therein are ejected by the ejector pins
 30. Simultaneously, the plungers 32 are slightly moved upward to eject
 disused resin from the pots 26. Then, the molded products are taken out
 from the lower die 20a. Note that, the molded products can be easily
 peeled off from the release film 50, so the molded products are left in
 the lower die 20b when the dies 20a and 20b are opened.
 After completing one cycle of the molding action, the work pieces 10 and
 the resin for the next molding cycle are set in the lower die 20b to mold
 the new work pieces 10. As described above, covering the upper face of the
 work pieces 10 with the release film 50 and molding the lower face thereof
 can be automatically executed by the resin molding machine of the present
 embodiment.
 By covering over the upper faces of the work pieces 10 with the release
 film 50, no resin invades onto the upper faces thereof while molding or
 encapsulating the lower side of the work pieces 10. The BGA circuit boards
 (the work pieces 10) have exposed the lands (terminals) on upper faces, so
 it is very important for providing reliable BGAs to mold or encapsulte the
 lower side without forming thin resin flash on the lands.
 By clamping the work pieces 10 with the release film 50, the clamping force
 can be securely applied to the edges of the cavities, so that forming
 resin flash can be effectively prevented. Further, deformation of the work
 pieces 10 can be prevented by the escaping sections 52 of the upper die
 20a, so that accuracy of the molded products can be improved.
 Many types of resin can be used in the resin molding machine. Namely,
 generally known resin, e.g., resin tablets formed into prescribed shapes,
 resin pellets, and resin wrapped with plastic film, can be used.
 Note that, to securely clamp the work pieces 10 by the molding dies 20a and
 20b, a depth of setting sections of the lower die 20b, in which the work
 pieces 10 are set, is slightly shallower than the thickness of the work
 pieces 10. In the case of multi layered BGA boards, etc., the thickness of
 the work pieces are not fixed. Therefore gaps are apt to be formed between
 the parting faces when the work pieces are clamped; and resin flash is apt
 to be formed in the gaps. However, in the present embodiment, the gaps are
 not formed because the release film 50 close the gaps, so that no resin
 flash is formed. To prevent forming the resin flash, the release film 50
 is required to have a sufficient thickness capable of closing said gaps
 and sufficient compressibility.
 If the depth of the setting sections are also deeper than the thickness of
 the work pieces 10, forming resin flash can be prevented by clamping the
 work pieces 10 with the release film 50.
 In the present embodiment, the characteristic points are the film feeding
 mechanism "G" provided to the fixed platen 5, which holds the upper die
 20a, and the air sucking mechanism including the air sucking holes 42 of
 the upper die 20a. The film feeding mechanism "G" and the air sucking
 mechanism can be attached to the conventional resin molding machines to
 execute the above described molding method in which the release film is
 used.
 In the present embodiment, conveying the work piece 10, conveying the
 molded products, feeding the release film 50, fixing the release film 50
 by air suction, etc. are controlled by a control section. In the case of
 using no release film, the control section does not execute the film
 feeding action and the film fixing action, so the resin molding machine of
 the present embodiment can be used for the conventional molding method in
 which no release film is used. Namely, the resin molding machine can
 execute not only the method of the present invention but also the
 conventional methods.
 In the present embodiment, slackened parts of the release film 50 are drawn
 into the drawing grooves 46, which are provided to enclose the escaping
 sections 52. When the release film 50 is fixed on the parting face of the
 upper die 20a, the release film 50 is expanded by the heat of the die 20a.
 By the expanded parts, wrinkles of the release film 50 are partially
 formed on the parting face of the die 20a. By the wrinkles of the release
 film 50, gaps are formed between the work pieces 10 and the release film
 50, and the melted resin may invade into the gaps. The resin invading into
 the gaps forms the resin flash. Further, the clamping force is
 concentrated to the wrinkles, so the work pieces 10 are apt to be damaged.
 The slackened parts of the release film 50 are drawn into the drawing
 grooves 46 by air suction, so that no wrinkles of the release film 50 are
 formed on the parting face. Air suction for removing the wrinkles are
 executed by air sucking holes 46a, each of which is located in the center
 of each drawing groove 46. Note that, if the cavities are formed in the
 parting face on which the release film is fixed, the drawing grooves can
 prevent the release film from forming the wrinkles in the cavities.
 By arranging the drawing grooves 46 to enclose the escaping sections 52, no
 wrinkles are formed at parts corresponding to the escaping sections 52. By
 drawing the slackened parts of the release film 50 into the drawing
 grooves 46 by sucking air through the air sucking holes 46a after the
 release film 50 is fixed on the parting face, no wrinkles are formed. If
 the slackened parts are broad and many wrinkles are formed, fixing the
 release film on the parting face by air suction is stopped, then tension
 is applied to the release film 50 to extend the wrinkles and the release
 film 50 is fixed again by air suction. The small wrinkles left are drawn
 into the drawing grooves 46. Note that, the air sucking holes 46a may be
 formed in the escaping sections 52.
 [Second Embodiment]
 The resin molding machine of a Second Embodiment is shown in FIG. 8. In the
 present embodiment, the cavities 28 are formed in the upper die 20a, and
 the lower die 20b has the setting sections in which the work pieces 10
 will be set. The release film 50 covers over almost the whole parting face
 of the upper die 20a as in the First Embodiment. The release film 50
 covers inner faces of the cavities 28 of the upper die 20a, so cavity air
 sucking holes 47, which look like slot holes, are opened along edges of a
 bottom face of each cavity 28.
 Since the release film 50 has sufficient softness and flexibility, the
 release film can be fixed along the inner faces of the cavities 28, as
 shown in FIG. 8, by sucking air through the air sucking holes 47 after the
 release film 50 is flatly fixed on the parting face by sucking the air
 through the air sucking holes 42. Therefore, the parting face and the
 inner faces of the cavities 28 can be covered with the release film 50.
 In the present embodiment, the inner faces of the cavities 28 are covered
 with the release film 50, so the molded products can be easily ejected
 from the upper die 20a, and no ejector pins are required.
 In the resin molding machine, the release film 50 is pressed onto the upper
 faces of the work pieces 10, which are molded or encapsulated with the
 resin, when the work pieces 10 are clamped with the release film 50.
 Therefore, no resin leaks from the cavities and the resin paths on the
 work pieces 10, so the work pieces 10 can be molded without forming the
 resin flash. In the case of molding or encapsulating the BGA circuit
 boards as the work pieces 10, there are formed electric cables on the
 upper face of the circuit boards, so the upper face thereof is not a flat
 face. However, the compressible release film 50 can absorb the unevenness
 of the electric cables, so no resin flash is formed on the surface.
 In the present embodiment, the whole lower face of the work pieces 10
 contact the lower die 20b, so the heat of the lower die 20b can be
 effectively conducted to the work pieces 10 and the resin in the cavities
 can be effectively solidified. If the work pieces 10 are BGA circuit
 boards, whose heat conductivity is low, and the cavities are formed in the
 lower die 20b, a contact area of the work pieces 10, which is capable of
 contacting the lower die 20b, is made narrow. Therefore, the work pieces
 10 cannot be effectively heated and the resin cannot be effectively
 solidified. In the case of molding one side of the work pieces, shrink of
 the solidifying resin causes deformation of molded parts when the
 solidification of the resin is delayed. However, in the present
 embodiment, the whole lower face of the work pieces 10 contact the lower
 die 20b, so they can be effectively heated by the lower die 20b and
 quality of the molded products can be improved.
 In the case of molding deformable work pieces, e.g., tape substrates, TAB
 tapes, step sections or concave sections, whose depth is equal to or
 higher than the thickness of the work pieces, are formed in the parting
 face. However, forming resin flash in the vicinity of the cavities and the
 resin paths can be prevented by the release film.
 [Third Embodiment]
 A Third Embodiment will be explained with reference to FIGS. 9 and 10. In
 the present embodiment, the molded product has electric terminals (leads),
 which are extended from two or four sides of a molded (encapsulated) part.
 The cavities 28 are formed in the lower die 20b, and the release film 50 is
 fixed on the parting face of the upper die 20a by the air suction as in
 the First Embodiment. In the present embodiment, the work pieces 10 are
 lead frames, bottom faces of the semiconductor chips 12 are exposed from
 the molded parts, and upper faces of the leads 11 are exposed from the
 molded parts.
 The leads 11 of the lead frames 10 are bent at mid parts, thereof so that
 the molded product (semiconductor device) can be located above a surface
 of a circuit board when the molded product is set on the circuit board. In
 FIG. 10, the lead frame 10 and the release film 50 are clamped by the dies
 20a and 20b, and the resin 35 is filled in the cavity 28a. The
 semiconductor chip 12 is fixed on a bottom face of the lead frame 10, so
 the semiconductor chip 12 is in the cavity 28a. The release film 50 is
 pressed on the upper (exposed) faces of the leads 11.
 Escaping pockets 54 are formed in the upper die 20a. The escaping pockets
 54 are located to correspond to the exposed faces of the leads 11. The
 release film 50 covers over the upper faces of the leads 11 when the work
 pieces 10 are clamped. By covering the release film 50, no resin is stuck
 on the upper faces of the leads 11. The exposed parts of the leads 11
 which are not supported by the lower die 20b or the parts of the leads 11
 which are in the cavities are bent when they are pressed by the release
 film 50. However, in the present embodiment, the upper die 20a has
 escaping pockets 54, so the release film 50 does not bend the leads 11.
 The escaping pockets 54 act as well as the escaping sections 52 of the
 upper die 20a of the First Embodiment.
 Inner parts of the leads 11, which are inside of the exposed parts, are not
 bent by the release film 50, so no escaping pockets 54 are required for
 those parts. The escaping pocket 54 is formed along the edges of the
 cavity 28a and located on the inner side of the edges. The escaping
 pockets 54 press the release film 50 onto the exposed parts of the leads
 11 so as to prevent forming of resin flash thereon, so the depth of the
 escaping pockets 54 is designed so as not to excessively press and bend
 the leads 11. When the lead frames 10 are clamped, the release film 50
 covering over the leads 11 is pressed into clearances "P" between the
 adjacent leads 11.
 A part of the release film 50, which is located on an outer side of the
 cavity 28a is clamped, with prescribed force, by the dies 20a and 20b.
 Therefore, the clamped part of the release film 50 is fully compressed.
 In FIG. 9, a state of setting the work piece 10 and the resin tablet 34 in
 the lower die 20b and fixing the release film 50 to the upper die 20a is
 shown on the left side of the center line CL; a state of clamping the work
 piece 10 and filling the melted resin 35 in the cavity 28 is shown on the
 right side of the center line CL.
 The molding action of the resin molding machine of the present embodiment
 is the same as that of the First Embodiment, so explanation will be
 omitted. In the case of molding SON-type semiconductor devices by the
 resin molding machine of the present embodiment, forming resin flash on
 surfaces of the terminals can be effectively prevented because exposed
 parts of leads of the work pieces can be securely covered with the release
 film 50. Thus, reliable SON-type semiconductor devices can be produced. In
 this case, the metal leads are exposed. In the case of tape or plastic
 substrates having circuits, etc., they can be similarly molded by the
 resin molding machine of the present embodiment.
 [Fourth Embodiment]
 A Fourth Embodiment will be explained with reference to FIG. 11. In the
 present embodiment, the semiconductor chips 12 are fully encapsulated with
 the resin 35. In the work piece 10, the leads 11 are bent at mid
 positions, so that a die pad 12a, on which the semiconductor chip 12 has
 been mounted, is located at a position slightly lower than the leads 11;
 the semiconductor chip 12 can be fully encapsulated in the resin 35.
 The cavities 28 are formed in the lower die 20b, the release film 50 is
 fixed on the parting face of the upper die 20a, the escaping pockets 54 of
 the upper die 20a absorb the thickness of the release film 50
 corresponding to base parts of the leads 11 as in the Third Embodiment. In
 the present embodiment too, by the release film 50, the work pieces can be
 encapsulated without forming resin flash on surfaces of the external
 terminals (outer leads).
 As described in the foregoing embodiments, the release film 50 is
 sandwiched between the work pieces 10 and the molding die, so the clamping
 force of the molding dies is applied to the work pieces 10 via the release
 film 50. The clamping force must not damage the work pieces 10.
 In an example shown in FIGS. 12 and 13, the clamping force applied to the
 work pieces 10 is reduced by the release film 50. FIGS. 12 and 13 show in
 the vicinity of the cavity in which the resin is filled.
 In FIG. 12, a supporting block 56, which is capable of supporting an upper
 face of the release film 50, is provided in the upper die 20a. The
 supporting block 56 faces the cavity 28 of the lower die 20b. A plurality
 of the supporting blocks 56 are respectively provided in block holes 58 of
 the upper die 20a. There is formed an air sucking hole 59, through which
 air is sucked to fix the release film 50, between outer side faces of the
 supporting block 56 and inner faces of the block hole 58. An air path 60
 is connected to the air sucking hole 59. The air path 60 is connected to
 an external air sucking mechanism, so that the air can be sucked through
 the air sucking holes 59.
 The escaping pockets 54, which have been explained are formed in the Third
 Embodiment, in a lower end face of the supporting block 56. The escaping
 pockets 54 absorb the thickness of the release film 50 so as not to
 excessively press the leads of the work piece 10. Furthermore, in the
 present embodiment, the slackened parts of the release film 50 can be
 drawn into the escaping pockets 54 by sucking air through the air sucking
 hole 59 and the air path 60 when the release film 50 is sucked onto the
 upper die 20a, so that wrinkles of the release film 50 can be removed.
 Without the wrinkles, the release film 50 never excessively presses the
 work piece 10.
 In FIG. 13, the release film 50 prevents the resin 35 from invading onto
 the upper face of the die pad 12a to expose the upper face thereof. There
 is provided a supporting section 56a, which is capable of supporting the
 upper face of the die pad 12a, at a lower end of the supporting block 56.
 The size of the supporting section 56 is designed according to the size of
 bends in the leads.
 The air sucking hole 59 is formed between the supporting block 56 and the
 block hole 58, the release film 50 covers over the parting face and the
 supporting block 56 of the upper die 20a, and the escaping pockets 54 are
 formed at the lower end of the supporting block 56 as in the example shown
 in FIG. 12.
 In this example, the slackened parts of the release film 50, which are
 expanded by the heat of the molding dies, are drawn by sucking air through
 the air path 60, and the die pad 12a of the work piece 10 is supported by
 the supporting section 56a, so that the die pad 12a can be fixed at a
 predetermined position and the work piece 10 can be molded while exposing
 the upper face of the die pad 12a and the upper faces of the outer leads.
 Another example is shown in FIG. 14. External terminals are bumps 13. To
 expose upper faces of the bumps 13 for electric connection, the release
 film 50 is fixed on the parting face of the upper die 20a by sucking air
 through the air sucking holes 47, and the release film 50 is pressed onto
 the upper faces of the bumps 13. The semiconductor chip 12 is molded or
 encapsulated by filling the resin 35 in the cavity 28a. An air sucking
 hole 47a is formed to fix the semiconductor chip 12 on an inner bottom
 face of the cavity 28a by air suction.
 In this example too, the release film 50 is pressed onto the upper faces of
 the bumps 13 while molding, so no resin flash is formed on the exposed
 faces of the bumps 13.
 This example can be applied to a method of molding circuit boards of IC
 cards, in which surfaces of terminals are exposed.
 [Fifth Embodiment]
 A Fifth Embodiment will be explained with reference to FIG. 15. The work
 pieces 10 of the present embodiment are lead frames having heat sinks 80.
 The upper die 20a has cavities 82 for accommodating the heat sinks 80. The
 parting face of the upper die 20a, which includes inner faces of the
 cavities 82, is covered with a sheet of release film 50. A state of
 setting the work piece 10 on the lower die 20b is shown on the left side
 of the center line CL. The semiconductor chip 12 is mounted on the lower
 face of the workpiece 10; the heat sink 80 is fixed on the upper face
 thereof. The work piece 10 is set in the lower die 20b. The semiconductor
 chip 12 is set in the cavity 28 of the lower die 20b.
 In FIG. 15, a state of clamping and molding the work piece 10 by the dies
 20a and 20b is shown on the right side of the center line CL. The release
 film 50 is pressed onto the upper exposed face of the heat sink 80, so no
 resin flash is formed thereon. The resin 35 molds or encapsulates not only
 the semiconductor chip 12 but also side faces of the heat sink 80. An area
 of the escaping section 52 is slightly broader than that of the heat sink
 80, so that no resin invades onto the upper face of the heat sink 80 and
 no resin flash is formed thereon.
 [Sixth Embodiment]
 A Sixth Embodiment will be explained with reference to FIG. 16. The work
 pieces 10 are lead frames for transistors having heat sinks 84. The
 semiconductor chips 12 are mounted on the heat sinks 84. A pluralilty of
 the heat sinks 84 are connected to the lead frame 10 at regular intervals.
 Dam sections of the die are fitted in spaces between the adjacent heat
 sinks 84 so as not to leak the resin therefrom. Cavities 86, in which the
 heat sinks 84 are accommodated, are formed in the upper die 20a.
 Furthermore, the parting face of the upper die 20a, which includes inner
 faces of the cavities 86, is covered with the release film 50.
 A state of opening the dies 20a and 20b and setting the work piece 10 is
 shown on the left side of the center line CL. The semiconductor chip 12 is
 mounted on the lower face of the work piece 10. The semiconductor chip 12
 is molded by filling the resin in the cavity 28 of the lower die 20b.
 The release film 50 is pressed onto an upper face of the heat sink 84, so
 no resin invades onto the upper face thereof and no resin flash is formed
 thereon.
 By clamping the work piece 10 with the release film 50, no resin flash is
 formed. This theory will be explained with further reference to FIGS. 33
 and 34. As to a front end of the heat sink 84, a gap "S" (see FIG. 33),
 which is formed between an end face of the heat sink 84 and a side face of
 a step part of the upper die 20a, is closed by the release film 50, so
 that no resin flash is formed at the front end of the heat sink 84. A gap
 "T" (see FIG. 33) between the parting faces of the dies 20a and 20b and a
 gap "U" (see FIG. 34) between the dam section and the parting face of the
 upper die 20a are closed by the release film 50, so that no resin flash is
 formed in the gaps. The release film 50, which is compressed by the dam
 section, closes gaps "V" (see FIG. 34) between each dam section and the
 work piece 10, so that no resin flash is formed on side faces of the work
 piece 10.
 [Seventh Embodiment]
 A Seventh Embodiment will be explained with reference to FIG. 17. The
 cavities 28 are formed in the upper die 20a; the work pieces 10 are set in
 the lower die 20b. Upper faces of the semiconductor chips 12 of the work
 pieces 10 are exposed.
 The release film 50 is fed on the lower die 20b, and the work pieces 10 are
 set on the release film 50. The release film 50 covers lower faces of
 outer leads of the work pieces 10 so as not to form the resin flash
 thereon.
 The structures of the molding dies 20a and 20b of the present embodiment
 are the inverted structures of the molding dies shown in FIG. 9. The work
 pieces 10 are arranged on both sides of the pots 26 of the lower die 20b,
 so two sheets of the release film 50 are fed. At least a side edge of the
 work piece 10, which is on the gate 40 side, should coincide with an inner
 side edge of the release film 50, so that the release film 50 is not
 lifted and no resin invades the lower side of the work piece.
 Upper ends of the guide pins 27, which are capable of correctly positioning
 the work pieces 10, are sharpened, so that they can break the release film
 50 when the work pieces 10 are clamped.
 In the present embodiment, the release film 50 is pressed onto electric
 terminals of the work pieces 10 as in the embodiment shown in FIG. 9; so
 that no resin flash is formed on the surfaces of the electric terminals
 and the molded products (semiconductor devices) can be securely connected
 on circuit boards.
 A modified example is shown in FIG. 18, two sheets of the release film 50
 are respectively fed to the parting faces of the dies 20a and 20b. The
 parting faces including the inner faces of the cavities 28 are covered
 with the release film 50. By covering the parting face of the upper die
 20a, an upper exposed face of the semiconductor chips 12 are covered with
 the release film 50, so that no resin invades onto the exposed faces and
 no resin flash is formed thereon.
 A second cavity 28a, whose area is slightly broader than that of the
 semiconductor chip 12, is formed in a ceiling face of each cavity 28. By
 forming the second cavity 28a, the invasion of the resin, toward the
 exposed face of the semiconductor chip 12, can be prevented. In this
 example, parts of side faces of the semiconductor chip 12 are exposed.
 Furthermore, stress applied to the the semiconductor chip 12, which is
 caused by the molding heat, can be effectively reduced.
 [Eighth Embodiment]
 An Eighth Embodiment will be explained with reference to FIG. 19. The
 semiconductor chips 12 are connected to a substrate of the work piece 10
 by flip-chip connection. The upper die 20a has cavities 28 for molding the
 semiconductor chips 12, and the release film 50 covers over the parting
 face of the upper die 20a including the cavities 28. Note that, no release
 film 50 is fed onto the parting face of the lower die 20b.
 The work pieces 10 are clamped by the dies 20a and 20b and the resin is
 introduced from the pots 26 to the cavities 28, so that the resin in
 filled in spaces between the semiconductor chips 12 and the substrate 10a.
 By exerting the melted resin, the resin can be securely filled in spaces
 between the adjacent bumps 13.
 By covering the upper faces of the semiconductor chips 12 with the release
 film 50, no resin flash is formed on the exposed upper faces of the
 semiconductor chips 12. Furthermore, by forming the second cavities 28a,
 parts of side faces of each semiconductor chip 12 can be exposed.
 Note that, in the resin molding machine shown in FIGS. 17-19, the gates 40
 of the resin paths are formed in the upper die 20a.
 [Ninth Embodiment]
 A Ninth Embodiment will be explained with reference to FIGS. 20-22. In the
 resin molding machine of the present embodiment, concave sections 90 are
 respectively formed in package sections (resin molded sections) of the
 products. Inner patterns 100a are exposed in each concave section 90, and
 CCD parts, etc. will be connected to the inner patterns 100a. The inner
 patterns 100a are inner leads and die pads of lead frames, circuit
 patterns on plastic circuit boards, etc. In the present example, the inner
 patterns 100a are exposed inner leads.
 A plan view of the molded package section is shown in FIG. 21. There is
 formed the concave section 90 in which a semiconductor chip, etc. is set,
 the inner leads 100a of the leads 100 are exposed on step sections 92 of
 the concave section 90. The concave section 90 is enclosed by a resin wall
 section 94.
 As shown in FIG. 20, the release film 50 is fixed on the parting face of
 the upper die 20a, which includes projected section 96 for forming the
 concave section 90, by air suction. When the leads 100 are clamped by the
 dies 20a and 20b, the release film 50 is pressed onto the exposed inner
 leads 100a, so that no resin flash is formed on the exposed inner leads
 100a. Since the exposed inner leads 100a act as electric terminals to
 which the semiconductor chips are connected, the resin molding machine of
 the present embodiment can produce reliable products.
 Note that, lower faces of the inner leads 100a are fixed on upper end faces
 of supporting members 99 by adhesive tape 101 so as not to shift the leads
 100. The supporting members 99 support the lower faces of the leads 100,
 so that the upper faces of the inner leads 100a can be securely pressed
 onto the release film 50 when the work pieces are clamped.
 In FIG. 22, molded sections 35 are formed on one side of the work pieces
 10. Since the work pieces 10 are supported by the lower die 20b, exposed
 parts of the work pieces 10 can be securely pressed and protected by the
 release film 50 by clamping the work pieces 10.
 [Tenth Embodiment]
 A Tenth Embodiment will be explained with reference to FIG. 23. The resin
 molding machine of the present embodiment molds or encapsulates
 multi-layered IC packages. The multi-layered IC package is made by piling
 a plurality of packages with mutual electrical connection, so surfaces of
 the leads must be exposed in both side faces of each package after
 molding.
 FIG. 23 shows a state of clamping the work piece 10 by the dies 20a and
 20b. Leads 102 of the work piece 10 are formed into an L-shape, and end
 sections of the leads 102 will be projected from a resin molded section
 (package section).
 The upper die 20a has the cavities 28 for encapsulating the semiconductor
 chips 12 with the resin. The parting face of the upper die 20a, which
 includes the cavities 28, and the parting face of the lower die 20b are
 respectively covered with the release film 50, and the work pieces 10 are
 clamped between the release film 50. By clamping the work pieces 10 with
 the release film 50, exposed parts of the leads 102, which will be
 projected from the resin molded sections of the products, are covered with
 the release film 50, so that no resin flash is formed on the exposed
 parts.
 A plurality of packages, which have been molded or encapsulated with the
 resin, are vertically piled to mutually electrically connect their leads
 102. In the resin molding machine of the present embodiment, no resin
 flash is formed on the surfaces of the leads 102, so that the packages can
 be securely electrically connected to each other and reliability of the IC
 packages can be improved.
 [Eleventh Embodiment]
 An Eleventh Embodiment will be explained with reference to FIGS. 24 and 25.
 The resin molding machine of the present embodiment makes optical packages
 108, in which rod-shaped lenses 104 (see FIG. 25) are held by a molded
 section 106. In the optical package 108, a plurality of the lenses 104 are
 held in the molded section 106, which is formed into a circular disc
 shape.
 In FIG. 24, the rod-shaped lenses 104 are vertically arranged and clamped
 by the dies 20a and 20b, and they are molded by filling the resin 35 in
 the cavities of the dies.
 The dies 20a and 20b respectively have cavities 21a and 21b, in which upper
 ends and lower ends of the lenses 104 are held. Two sheets of the release
 film 50 are respectively fed on the parting faces of the dies 20a and 20b
 to mold the molded section 106. In the cavities 21a and 21b, the release
 film 50 covers over outer faces of the lenses 104, so no resin 35 invades
 onto the outer faces of the lenses 104 when the resin 35 is filled. Since
 the lenses 104 are optical parts, resin flash must not be formed on the
 outer faces. Therefore, reliable products can be produced by the resin
 molding machine of the present embodiment.
 By having enough flexibility and extensibility, the release film 50 can be
 easily deformed along external shapes of the lenses 104, and exposed parts
 of the lenses 104 can be securely covered with the release film 50. To
 form the cavities 21a and 21b, in which the release film 50 covers the
 ends of the lenses 104, holding members 110 may be provided in the
 cavities 21a and 21b as shown in FIG. 24. By clamping the lenses 104, by
 the dies 20a and 20b, with the release film 50, the release film 50 is
 extended and fits and covers over the ends of the lenses 104.
 [Twelfth Embodiment]
 A Twelfth Embodiment will be explained with reference to FIGS. 26 and 27.
 The resin molding machine of the present embodiment molds a holding
 section 116 of an optical cable 112, which includes a plurality of optical
 fibers, with resin. The holding section 116 bundles the optical fibers as
 one optical cable 112. In FIG. 26, the optical cable 112 is held, by the
 dies 20a and 20b, with the release film 50, and the resin 35 is filled in
 the cavity 28. A pusher 114 presses the release film 50 onto an upper end
 face of the optical cable 112 to prevent the resin from sticking thereon.
 By pushing the release film 50, which has sufficient elasticity, onto the
 upper end face of the optical cable 112, no resin 35 invades onto the
 upper end face thereof while molding.
 By molding the holding section 116 of the optical cable 112 with the resin
 35, the optical cable 112 can be attached to a predetermined place with
 high positioning accuracy. By molding with the release film 50, the end
 face of the optical cable (end faces of the optical fibers) can be clean
 without sticking resin flash, dusts, etc. The optical cable 112 having the
 molded holding section 116 is shown in FIG. 27.
 [Thirteenth Embodiment]
 A Thirteenth Embodiment will be explained with reference to FIGS. 28 and
 29. The resin molding machine of the present embodiment molds pin grid
 parts. Each of the pin grid parts has a plastic base board 123, which will
 be molded, and a plurality of pins 120, which will be vertically extended
 from the base board 121. Heads sections 120a of the pins 120 will be
 projected from a bottom face of the base board 121.
 In FIG. 28, the pins 120 are set in the lower die 20b. The pins 120 are
 pierced through a tape-shaped pin holder 122 so as to vertically set the
 pins 120 in the lower die 20b. The pins 120 are set in the lower die 20b
 together with the pin holder 122. The tape-shaped pin holder 122 may be
 made from the film materials of the release film 50. In the case of
 film-formed pin holder 122, it may be fed by the film feeding mechanism
 for feeding the release film 50.
 Through-holes 124, which are arranged to correspond to the pins 120, are
 bored in the lower die 20b; supporting pins 126, which respectively
 support the pins 120, are provided in each through-hole 124. The
 supporting pins 126 are always biased upward by springs 128.
 The upper die 20a has the cavities 28, and the release film 50 is fed on
 the parting face of the upper die 20a including the cavities 28. The depth
 of the cavities 28 define the height of the base boards 121 of the pin
 grid parts. The ceiling faces of the cavities 28 push the head sections
 120a of the pins 120. In the present embodiment, the head sections 120a of
 the pins 120 are pressed onto the release film 50 while molding. The
 springs 128 always bias the pins 120 upward, and the ceiling faces of the
 cavities 28 securely press the release film 50 onto the head sections 120a
 of the pins 120 when the dies 20a and 20b are closed.
 In the present embodiment, upper end faces of the head sections 120a of the
 pins 120 are securely covered with the release film 50 while molding, so
 no resin flash is formed on the exposed (upper) faces of the head sections
 120a. Furthermore, the head sections 120a can be securely electrically
 connected by wire bonding, etc. Further, by piercing the pins 120 through
 the pin holder 122, no resin flash is formed on exposed parts of the pins
 120.
 In FIG. 29, the escaping sections 52, which correspond to the pins 120, are
 formed in the upper die 20a, so that resin invasion can be further
 prevented by the release film 50. In the present embodiment, the upper end
 faces of the head sections 120a coincide with the upper face of the base
 board 121, but they may be projected from or retracted in the upper face
 of the base board 121.
 [Fourteenth Embodiment]
 A Fourteenth Embodiment will be explained with reference to FIG. 30. In the
 present embodiment, the wide release film 50 is fed to the upper die 20a;
 and two sheet of the narrow release film 50 are fed to the lower die 20b
 and arranged on each side of the pot 26.
 Work pieces 10 are clamped with the release film 50 and molded or
 encapsulated with the resin 34, so no resin invades the parts of the work
 pieces 10, which are covered with the release film 50.
 Some types of lead frames, e.g., palladium plated lead frames, need no
 surface treatment, so it is advantageous for them to prevent the resin
 from invading onto their leads.
 The resin molding machine of the present embodiment is capable of molding
 or encapsulating lead frames having no dam bars with resin. Since the
 release film 50 has high flexibility and compressibility, the release film
 50 having proper thickness is capable of entering and closing spaces
 between the adjacent leads, so the release film 50 act as the dam bars
 while molding.
 Note that, in the above described embodiments, the pots 26 are provided in
 the lower dies 20b, but the present invention can be applied to the resin
 molding machine whose pots 26 are provided in the upper die 20a. In the
 both types of the resin molding machines, the method of the present
 invention can be executed by feeding the release film 50 to at least one
 of the molding dies 20a and 20b.
 The invention may be embodied in other specific forms without departing
 from the spirit or essential characteristics thereof. The present
 embodiments are therefore to be considered in all respects as illustrative
 and restrictive, the scope of the invention being indicated by the
 appended claims rather than by the foregoing description and all changes
 which come within the meaning and range of equivalency of the claims are
 therefore intended to be embraced therein.